Knee Ligament Injuries

Anterior Cruciate Ligament (ACL) Injury

Definition

An anterior cruciate ligament Anterior Cruciate Ligament A strong ligament of the knee that originates from the posteromedial portion of the lateral condyle of the femur, passes anteriorly and inferiorly between the condyles, and attaches to the depression in front of the intercondylar eminence of the tibia. Knee Joint: Anatomy ( ACL ACL A strong ligament of the knee that originates from the posteromedial portion of the lateral condyle of the femur, passes anteriorly and inferiorly between the condyles, and attaches to the depression in front of the intercondylar eminence of the tibia. Knee Joint: Anatomy) injury causes structural damage to the anterior cruciate ligament Anterior Cruciate Ligament A strong ligament of the knee that originates from the posteromedial portion of the lateral condyle of the femur, passes anteriorly and inferiorly between the condyles, and attaches to the depression in front of the intercondylar eminence of the tibia. Knee Joint: Anatomy. The functions of the ligament are to:

• Control anterior translation Translation Translation is the process of synthesizing a protein from a messenger RNA (mRNA) transcript. This process is divided into three primary stages: initiation, elongation, and termination. Translation is catalyzed by structures known as ribosomes, which are large complexes of proteins and ribosomal RNA (rRNA). Stages and Regulation of Translation of the tibia Tibia The second longest bone of the skeleton. It is located on the medial side of the lower leg, articulating with the fibula laterally, the talus distally, and the femur proximally. Knee Joint: Anatomy on the femur
• Restrict tibial internal/ external rotation External Rotation Examination of the Upper Limbs on the femur  
• Restrict varus/valgus deviation of the tibia Tibia The second longest bone of the skeleton. It is located on the medial side of the lower leg, articulating with the fibula laterally, the talus distally, and the femur proximally. Knee Joint: Anatomy on the femur

Anatomy

• Originates at the posteromedial aspect of the lateral femoral condyle, posterior to the longitudinal axis of the femur
• Runs inferiorly, medially, and anteriorly 
• Attaches to the anteromedial aspect of the tibia Tibia The second longest bone of the skeleton. It is located on the medial side of the lower leg, articulating with the fibula laterally, the talus distally, and the femur proximally. Knee Joint: Anatomy between the condyles

Epidemiology

• Incidence Incidence The number of new cases of a given disease during a given period in a specified population. It also is used for the rate at which new events occur in a defined population. It is differentiated from prevalence, which refers to all cases in the population at a given time. Measures of Disease Frequency: 68.6 per 100,000/year in the United States
  • Peak incidence Incidence The number of new cases of a given disease during a given period in a specified population. It also is used for the rate at which new events occur in a defined population. It is differentiated from prevalence, which refers to all cases in the population at a given time. Measures of Disease Frequency in men: between 19 and 25 years; related to sports
  • Peak incidence Incidence The number of new cases of a given disease during a given period in a specified population. It also is used for the rate at which new events occur in a defined population. It is differentiated from prevalence, which refers to all cases in the population at a given time. Measures of Disease Frequency in women: 14–18 years 
• Most commonly injured ligament in the knee
• Athletes and trauma patients Patients Individuals participating in the health care system for the purpose of receiving therapeutic, diagnostic, or preventive procedures. Clinician–Patient Relationship are the most commonly affected.

Etiology

• Noncontact mechanism (rotational forces):
  • Skiers
  • Baseball players
  • Soccer players
  • Basketball players
• Contact mechanism (direct blunt trauma to the knee): football players

Clinical presentation

Patients Patients Individuals participating in the health care system for the purpose of receiving therapeutic, diagnostic, or preventive procedures. Clinician–Patient Relationship with an ACL ACL A strong ligament of the knee that originates from the posteromedial portion of the lateral condyle of the femur, passes anteriorly and inferiorly between the condyles, and attaches to the depression in front of the intercondylar eminence of the tibia. Knee Joint: Anatomy injury present with pain Pain An unpleasant sensation induced by noxious stimuli which are detected by nerve endings of nociceptive neurons. Pain: Types and Pathways and report recent high-energy blunt trauma to the knee.

History:

• Patient reports hearing or feeling a “pop” and that the affected knee “gave out” at the time of injury.
• Also important to delineate:
  • Timing 
  • Mechanism of trauma
  • Site of injury
  • Further details of the specific situation

Physical examination:

• Antalgic gait Antalgic Gait Legg-Calvé-Perthes Disease
• Tenderness to palpation Palpation Application of fingers with light pressure to the surface of the body to determine consistency of parts beneath in physical diagnosis; includes palpation for determining the outlines of organs. Dermatologic Examination along the joint line
• Edema Edema Edema is a condition in which excess serous fluid accumulates in the body cavity or interstitial space of connective tissues. Edema is a symptom observed in several medical conditions. It can be categorized into 2 types, namely, peripheral (in the extremities) and internal (in an organ or body cavity). Edema around the knee joint Knee joint The knee joint is made up of the articulations between the femur, tibia, and patella bones, and is one of the largest and most complex joints of the human body. The knee is classified as a synovial hinge joint, which primarily allows for flexion and extension with a more limited degree of translation and rotation. Knee Joint: Anatomy
• Decreased range of motion Range of motion The distance and direction to which a bone joint can be extended. Range of motion is a function of the condition of the joints, muscles, and connective tissues involved. Joint flexibility can be improved through appropriate muscle strength exercises. Examination of the Upper Limbs
• Knee instability tests:
  • Anterior drawer maneuver: 
    • The patient lies supine with hips flexed to 45 degrees, knee at a 90-degree angle, and feet flat on the exam table. 
    • The clinician Clinician A physician, nurse practitioner, physician assistant, or another health professional who is directly involved in patient care and has a professional relationship with patients. Clinician–Patient Relationship stabilizes the leg Leg The lower leg, or just “leg” in anatomical terms, is the part of the lower limb between the knee and the ankle joint. The bony structure is composed of the tibia and fibula bones, and the muscles of the leg are grouped into the anterior, lateral, and posterior compartments by extensions of fascia. Leg: Anatomy by sitting on the patient’s toes and holds the proximal tibia Tibia The second longest bone of the skeleton. It is located on the medial side of the lower leg, articulating with the fibula laterally, the talus distally, and the femur proximally. Knee Joint: Anatomy with both hands and pulls anteriorly. 
    • Positive test: Proximal tibia Tibia The second longest bone of the skeleton. It is located on the medial side of the lower leg, articulating with the fibula laterally, the talus distally, and the femur proximally. Knee Joint: Anatomy will slide anteriorly, like a drawer being opened.
  •   Pivot shift Pivot Shift Examination of the Lower Limbs test:
    • The patient lies supine with the knee fully extended.
    • The clinician Clinician A physician, nurse practitioner, physician assistant, or another health professional who is directly involved in patient care and has a professional relationship with patients. Clinician–Patient Relationship places an  internal rotation Internal Rotation Examination of the Upper Limbs and valgus force on the proximal  tibia Tibia The second longest bone of the skeleton. It is located on the medial side of the lower leg, articulating with the fibula laterally, the talus distally, and the femur proximally. Knee Joint: Anatomy while carrying the knee into passive  flexion Flexion Examination of the Upper Limbs.
    • The test is positive if the knee becomes unstable and subluxated; even a “clunk” sound could be produced. 
  • Lachman test:
    • The patient lies supine with the affected knee at a 30-degree angle. 
    • The clinician Clinician A physician, nurse practitioner, physician assistant, or another health professional who is directly involved in patient care and has a professional relationship with patients. Clinician–Patient Relationship stabilizes the distal femur with the left hand Hand The hand constitutes the distal part of the upper limb and provides the fine, precise movements needed in activities of daily living. It consists of 5 metacarpal bones and 14 phalanges, as well as numerous muscles innervated by the median and ulnar nerves. Hand: Anatomy and pulls on the tibia Tibia The second longest bone of the skeleton. It is located on the medial side of the lower leg, articulating with the fibula laterally, the talus distally, and the femur proximally. Knee Joint: Anatomy toward themselves.
    • Positive test: anterior displacement Displacement The process by which an emotional or behavioral response that is appropriate for one situation appears in another situation for which it is inappropriate. Defense Mechanisms

Diagnosis

Diagnosis is made clinically and confirmed by imaging.

• MRI is the preferred imaging method:
  • Primary signs:
    • Hyperintensity of the ACL ACL A strong ligament of the knee that originates from the posteromedial portion of the lateral condyle of the femur, passes anteriorly and inferiorly between the condyles, and attaches to the depression in front of the intercondylar eminence of the tibia. Knee Joint: Anatomy (usually at the midportion)
    • Discontinuity of ligament fibers
    • Alteration of Blumensaat’s line
    • Edema Edema Edema is a condition in which excess serous fluid accumulates in the body cavity or interstitial space of connective tissues. Edema is a symptom observed in several medical conditions. It can be categorized into 2 types, namely, peripheral (in the extremities) and internal (in an organ or body cavity). Edema
  • Secondary signs:
    • Bone marrow Bone marrow The soft tissue filling the cavities of bones. Bone marrow exists in two types, yellow and red. Yellow marrow is found in the large cavities of large bones and consists mostly of fat cells and a few primitive blood cells. Red marrow is a hematopoietic tissue and is the site of production of erythrocytes and granular leukocytes. Bone marrow is made up of a framework of connective tissue containing branching fibers with the frame being filled with marrow cells. Bone Marrow: Composition and Hematopoiesis edema Edema Edema is a condition in which excess serous fluid accumulates in the body cavity or interstitial space of connective tissues. Edema is a symptom observed in several medical conditions. It can be categorized into 2 types, namely, peripheral (in the extremities) and internal (in an organ or body cavity). Edema
    • Associated medial collateral ligament Medial collateral ligament Knee Joint: Anatomy injury
    • Anterior tibial translation Translation Translation is the process of synthesizing a protein from a messenger RNA (mRNA) transcript. This process is divided into three primary stages: initiation, elongation, and termination. Translation is catalyzed by structures known as ribosomes, which are large complexes of proteins and ribosomal RNA (rRNA). Stages and Regulation of Translation > 7 mm
• X-ray X-ray Penetrating electromagnetic radiation emitted when the inner orbital electrons of an atom are excited and release radiant energy. X-ray wavelengths range from 1 pm to 10 nm. Hard x-rays are the higher energy, shorter wavelength x-rays. Soft x-rays or grenz rays are less energetic and longer in wavelength. The short wavelength end of the x-ray spectrum overlaps the gamma rays wavelength range. The distinction between gamma rays and x-rays is based on their radiation source. Pulmonary Function Tests is useful only to rule out fractures.
• Arthroscopy: uses an instrument (arthroscope) inserted into the joint through a small incision
  • Gold standard for diagnosis
  • Minimally invasive surgical procedure used for diagnosis; may also be used for the treatment of meniscal tears

Management

• Conservative management: in patients Patients Individuals participating in the health care system for the purpose of receiving therapeutic, diagnostic, or preventive procedures. Clinician–Patient Relationship with low functional demand
  • Rest, Ice, Compression, and Elevation (RICE)
  • No weight-bearing (use crutches or wheelchair)
  • NSAIDs NSAIDS Primary vs Secondary Headaches for pain Pain An unpleasant sensation induced by noxious stimuli which are detected by nerve endings of nociceptive neurons. Pain: Types and Pathways relief
• Orthopedic surgery consultation and surgical management for reconstruction using a tissue graft Graft A piece of living tissue that is surgically transplanted Organ Transplantation is done in:
  • Athletes 
  • Young, active patients Patients Individuals participating in the health care system for the purpose of receiving therapeutic, diagnostic, or preventive procedures. Clinician–Patient Relationship
  • Significant knee instability
  • Injury to multiple structures of the knee
• Rehabilitation with physical therapy Physical Therapy Becker Muscular Dystrophy:
  • Improves functionality 
  • Increases knee stability
• Prognosis Prognosis A prediction of the probable outcome of a disease based on a individual’s condition and the usual course of the disease as seen in similar situations. Non-Hodgkin Lymphomas: 90% of patients Patients Individuals participating in the health care system for the purpose of receiving therapeutic, diagnostic, or preventive procedures. Clinician–Patient Relationship will return to normal functioning after repair.

Differential diagnosis of ACL tear ACL tear Knee Pain

• Meniscal tear: injury to the meniscus caused by rotational or shearing forces Shearing forces Vascular Resistance, Flow, and Mean Arterial Pressure across the tibiofemoral joint Tibiofemoral joint Knee Joint: Anatomy. Clinical presentation includes a history of a twisting or rotational injury followed by joint line pain Pain An unpleasant sensation induced by noxious stimuli which are detected by nerve endings of nociceptive neurons. Pain: Types and Pathways associated with a small effusion. Some patients Patients Individuals participating in the health care system for the purpose of receiving therapeutic, diagnostic, or preventive procedures. Clinician–Patient Relationship may also present with mechanical symptoms, such as joint locking, clicking, or catching.
• Posterior knee dislocation Posterior Knee Dislocation Knee Dislocation: pathologic loss of articulation of the knee joint Knee joint The knee joint is made up of the articulations between the femur, tibia, and patella bones, and is one of the largest and most complex joints of the human body. The knee is classified as a synovial hinge joint, which primarily allows for flexion and extension with a more limited degree of translation and rotation. Knee Joint: Anatomy due to high-energy trauma such as that due to motor-vehicle collisions or low-energy trauma Low-Energy Trauma Toddler’s Fractures such as that seen in athletic training.
• Fracture Fracture A fracture is a disruption of the cortex of any bone and periosteum and is commonly due to mechanical stress after an injury or accident. Open fractures due to trauma can be a medical emergency. Fractures are frequently associated with automobile accidents, workplace injuries, and trauma. Overview of Bone Fractures of the tibial spine Spine The human spine, or vertebral column, is the most important anatomical and functional axis of the human body. It consists of 7 cervical vertebrae, 12 thoracic vertebrae, and 5 lumbar vertebrae and is limited cranially by the skull and caudally by the sacrum. Vertebral Column: Anatomy or femoral or tibial epiphysis Tibial Epiphysis Blount’s Disease: diagnosed on X-ray X-ray Penetrating electromagnetic radiation emitted when the inner orbital electrons of an atom are excited and release radiant energy. X-ray wavelengths range from 1 pm to 10 nm. Hard x-rays are the higher energy, shorter wavelength x-rays. Soft x-rays or grenz rays are less energetic and longer in wavelength. The short wavelength end of the x-ray spectrum overlaps the gamma rays wavelength range. The distinction between gamma rays and x-rays is based on their radiation source. Pulmonary Function Tests and managed by an orthopedic specialist.
• Medial collateral knee ligament injury: structural damage to the medial collateral ligament Medial collateral ligament Knee Joint: Anatomy (function is to provide valgus stability to the knee)

Medial Collateral Ligament (MCL) Injury

Definition

A medial collateral ligament Medial collateral ligament Knee Joint: Anatomy ( MCL MCL Knee Joint: Anatomy) injury causes structural damage to the ligament whose function is to provide valgus stability to the knee.

Unhappy triad: simultaneous injury of the MCL MCL Knee Joint: Anatomy, ACL ACL A strong ligament of the knee that originates from the posteromedial portion of the lateral condyle of the femur, passes anteriorly and inferiorly between the condyles, and attaches to the depression in front of the intercondylar eminence of the tibia. Knee Joint: Anatomy, and the medial meniscus Medial Meniscus Meniscus Tear

Anatomy

• Originates from the medial epicondyle Medial epicondyle Arm: Anatomy of the femur and runs to the medial condyle of the tibia Tibia The second longest bone of the skeleton. It is located on the medial side of the lower leg, articulating with the fibula laterally, the talus distally, and the femur proximally. Knee Joint: Anatomy 
• Attaches in 2 places on the tibia Tibia The second longest bone of the skeleton. It is located on the medial side of the lower leg, articulating with the fibula laterally, the talus distally, and the femur proximally. Knee Joint: Anatomy

Epidemiology

• 40% of all knee injuries
• 60% of knee injuries while skiing involve the MCL MCL Knee Joint: Anatomy.

Etiology

• Sudden, high-energy twisting or turning motions (rotational forces):
  • Skiers
  • Baseball players
  • Soccer players
  • Basketball players
• Blunt trauma (direct blow to the lateral aspect of the knee) 

Clinical presentation

Patients Patients Individuals participating in the health care system for the purpose of receiving therapeutic, diagnostic, or preventive procedures. Clinician–Patient Relationship with MCL MCL Knee Joint: Anatomy injury present with pain Pain An unpleasant sensation induced by noxious stimuli which are detected by nerve endings of nociceptive neurons. Pain: Types and Pathways and report recent trauma to the knee. The exam is ideally done in the 1st 20–30 minutes, before swelling Swelling Inflammation interferes with the exam.

History:

• Patient reports hearing or feeling a pop and that the affected knee feels unstable.
• Also important to delineate:
  • Timing 
  • Mechanism of trauma
  • Site of injury
  • Further details of the specific situation

Physical examination:

• Antalgic gait Antalgic Gait Legg-Calvé-Perthes Disease
• Pain Pain An unpleasant sensation induced by noxious stimuli which are detected by nerve endings of nociceptive neurons. Pain: Types and Pathways on palpation Palpation Application of fingers with light pressure to the surface of the body to determine consistency of parts beneath in physical diagnosis; includes palpation for determining the outlines of organs. Dermatologic Examination along the course of the MCL MCL Knee Joint: Anatomy
• Edema Edema Edema is a condition in which excess serous fluid accumulates in the body cavity or interstitial space of connective tissues. Edema is a symptom observed in several medical conditions. It can be categorized into 2 types, namely, peripheral (in the extremities) and internal (in an organ or body cavity). Edema/ ecchymosis Ecchymosis Extravasation of blood into the skin, resulting in a nonelevated, rounded or irregular, blue or purplish patch, larger than a petechia. Orbital Fractures on the medial aspect of the knee
• Decreased range of motion Range of motion The distance and direction to which a bone joint can be extended. Range of motion is a function of the condition of the joints, muscles, and connective tissues involved. Joint flexibility can be improved through appropriate muscle strength exercises. Examination of the Upper Limbs
• Knee instability test (valgus stress test):
  • The patient lies supine with the affected limb abducted off the examination table and the knee fully extended.
  • The clinician Clinician A physician, nurse practitioner, physician assistant, or another health professional who is directly involved in patient care and has a professional relationship with patients. Clinician–Patient Relationship holds the ipsilateral ankle with 1 hand Hand The hand constitutes the distal part of the upper limb and provides the fine, precise movements needed in activities of daily living. It consists of 5 metacarpal bones and 14 phalanges, as well as numerous muscles innervated by the median and ulnar nerves. Hand: Anatomy and applies valgus pressure on the knee.
  • The test is positive if joint opening and pain Pain An unpleasant sensation induced by noxious stimuli which are detected by nerve endings of nociceptive neurons. Pain: Types and Pathways are detected. 
• Grades of instability in MCL MCL Knee Joint: Anatomy injuries:
  • Grade I: pain Pain An unpleasant sensation induced by noxious stimuli which are detected by nerve endings of nociceptive neurons. Pain: Types and Pathways along the course of the MCL MCL Knee Joint: Anatomy with no joint opening
  • Grade II: partial opening of the joint
  • Grade III: significant joint opening

Diagnosis

Diagnosis is made clinically and later confirmed by imaging studies.

• MRI is the preferred imaging method: allows for examination of neighboring structures
• Ultrasonography may be a more accessible alternative to MRI.
• X-ray X-ray Penetrating electromagnetic radiation emitted when the inner orbital electrons of an atom are excited and release radiant energy. X-ray wavelengths range from 1 pm to 10 nm. Hard x-rays are the higher energy, shorter wavelength x-rays. Soft x-rays or grenz rays are less energetic and longer in wavelength. The short wavelength end of the x-ray spectrum overlaps the gamma rays wavelength range. The distinction between gamma rays and x-rays is based on their radiation source. Pulmonary Function Tests is useful only to rule out fractures.

Management

• Conservative management: in patients Patients Individuals participating in the health care system for the purpose of receiving therapeutic, diagnostic, or preventive procedures. Clinician–Patient Relationship with low functional demand
  • RICE
  • No weight-bearing (use crutches or wheelchair)
  • NSAIDs NSAIDS Primary vs Secondary Headaches for pain Pain An unpleasant sensation induced by noxious stimuli which are detected by nerve endings of nociceptive neurons. Pain: Types and Pathways relief
• Orthopedic surgery consultation and surgical management:
  • Indicated in all cases for evaluation and treatment options
  • Surgical management is performed in grade III injuries with or without concomitant injuries.
• Rehabilitation with physical therapy Physical Therapy Becker Muscular Dystrophy:
  • Return-to-play protocol: progressive increase in the difficulty of exercises
  • Program must be as comprehensive as possible to ensure maximal recovery of functionality.
• Prognosis Prognosis A prediction of the probable outcome of a disease based on a individual’s condition and the usual course of the disease as seen in similar situations. Non-Hodgkin Lymphomas: 98% of patients Patients Individuals participating in the health care system for the purpose of receiving therapeutic, diagnostic, or preventive procedures. Clinician–Patient Relationship with grade I and II injuries will experience a full recovery with conservative management.
  • Grade I injuries: typically can return to athletic activity in 10–14 days
  • Grade II and III injuries: variable Variable Variables represent information about something that can change. The design of the measurement scales, or of the methods for obtaining information, will determine the data gathered and the characteristics of that data. As a result, a variable can be qualitative or quantitative, and may be further classified into subgroups. Types of Variables recovery times

Differential diagnosis of MCL MCL Knee Joint: Anatomy tear

• Slipped capital femoral epiphysis Epiphysis The head of a long bone that is separated from the shaft by the epiphyseal plate until bone growth stops. At that time, the plate disappears and the head and shaft are united. Bones: Structure and Types: orthopedic disorder of early adolescence characterized by the pathologic “slipping,” or displacement Displacement The process by which an emotional or behavioral response that is appropriate for one situation appears in another situation for which it is inappropriate. Defense Mechanisms, of the femoral head, or epiphysis Epiphysis The head of a long bone that is separated from the shaft by the epiphyseal plate until bone growth stops. At that time, the plate disappears and the head and shaft are united. Bones: Structure and Types, on the femoral neck Neck The part of a human or animal body connecting the head to the rest of the body. Peritonsillar Abscess. Slipped capital femoral epiphysis Epiphysis The head of a long bone that is separated from the shaft by the epiphyseal plate until bone growth stops. At that time, the plate disappears and the head and shaft are united. Bones: Structure and Types is considered a type I Salter-Harris growth plate fracture Growth Plate Fracture Slipped Capital Femoral Epiphysis, and it affects boys twice as often as girls. 
• Osteoarthritis Osteoarthritis Osteoarthritis (OA) is the most common form of arthritis, and is due to cartilage destruction and changes of the subchondral bone. The risk of developing this disorder increases with age, obesity, and repetitive joint use or trauma. Patients develop gradual joint pain, stiffness lasting < 30 minutes, and decreased range of motion. Osteoarthritis: most common form of arthritis Arthritis Acute or chronic inflammation of joints. Osteoarthritis due to cartilage Cartilage Cartilage is a type of connective tissue derived from embryonic mesenchyme that is responsible for structural support, resilience, and the smoothness of physical actions. Perichondrium (connective tissue membrane surrounding cartilage) compensates for the absence of vasculature in cartilage by providing nutrition and support. Cartilage: Histology destruction and changes of the subchondral bone Subchondral Bone Osteochondritis Dissecans. The risk of developing osteoarthritis Osteoarthritis Osteoarthritis (OA) is the most common form of arthritis, and is due to cartilage destruction and changes of the subchondral bone. The risk of developing this disorder increases with age, obesity, and repetitive joint use or trauma. Patients develop gradual joint pain, stiffness lasting < 30 minutes, and decreased range of motion. Osteoarthritis increases with age, obesity Obesity Obesity is a condition associated with excess body weight, specifically with the deposition of excessive adipose tissue. Obesity is considered a global epidemic. Major influences come from the western diet and sedentary lifestyles, but the exact mechanisms likely include a mixture of genetic and environmental factors. Obesity, and repetitive joint use or trauma. Patients Patients Individuals participating in the health care system for the purpose of receiving therapeutic, diagnostic, or preventive procedures. Clinician–Patient Relationship develop gradual joint pain Pain An unpleasant sensation induced by noxious stimuli which are detected by nerve endings of nociceptive neurons. Pain: Types and Pathways, stiffness lasting < 30 minutes, and decreased range of motion Range of motion The distance and direction to which a bone joint can be extended. Range of motion is a function of the condition of the joints, muscles, and connective tissues involved. Joint flexibility can be improved through appropriate muscle strength exercises. Examination of the Upper Limbs.

Lateral Collateral Ligament (LCL) Injury

Definition

A lateral collateral ligament Lateral collateral ligament Knee Joint: Anatomy (LCL) injury causes structural damage to the ligament whose function is to prevent varus angulation Angulation Buckle or Torus Fracture of the knee.

Anatomy

• Originates from the lateral epicondyle Lateral epicondyle Arm: Anatomy of the femur and runs on the outside of the knee
• Attaches on the fibular head
• Is narrower than the MCL MCL Knee Joint: Anatomy and is not fused with the capsular ligament or lateral meniscus
• Is more flexible than the MCL MCL Knee Joint: Anatomy and is less susceptible to injury

Epidemiology and etiology

• Least common of all ligamentous knee injuries
• Rarely seen in isolation; usually accompanies other injuries of the knee
• Women and athletes are considered at increased risk:
  • Tennis
  • Gymnastics
• Can also be due to direct blunt trauma to the anteromedial aspect of the knee, causing extreme hyperextension and varus stress

Clinical presentation

History: 

The patient reports trauma to the medial aspect of the knee followed by varus bending.

Physical examination:

• Antalgic gait Antalgic Gait Legg-Calvé-Perthes Disease
• Pain Pain An unpleasant sensation induced by noxious stimuli which are detected by nerve endings of nociceptive neurons. Pain: Types and Pathways on palpation Palpation Application of fingers with light pressure to the surface of the body to determine consistency of parts beneath in physical diagnosis; includes palpation for determining the outlines of organs. Dermatologic Examination along the joint line
• Lower limb weakness and/or foot drop Foot Drop Leprosy
• Edema Edema Edema is a condition in which excess serous fluid accumulates in the body cavity or interstitial space of connective tissues. Edema is a symptom observed in several medical conditions. It can be categorized into 2 types, namely, peripheral (in the extremities) and internal (in an organ or body cavity). Edema around the knee joint Knee joint The knee joint is made up of the articulations between the femur, tibia, and patella bones, and is one of the largest and most complex joints of the human body. The knee is classified as a synovial hinge joint, which primarily allows for flexion and extension with a more limited degree of translation and rotation. Knee Joint: Anatomy
• Decreased range of motion Range of motion The distance and direction to which a bone joint can be extended. Range of motion is a function of the condition of the joints, muscles, and connective tissues involved. Joint flexibility can be improved through appropriate muscle strength exercises. Examination of the Upper Limbs
• Knee instability tests:
  • Varus stress test: 
    • The patient lies supine with the affected knee at a 30-degree angle. 
    • The clinician Clinician A physician, nurse practitioner, physician assistant, or another health professional who is directly involved in patient care and has a professional relationship with patients. Clinician–Patient Relationship stabilizes the distal femur with 1 hand Hand The hand constitutes the distal part of the upper limb and provides the fine, precise movements needed in activities of daily living. It consists of 5 metacarpal bones and 14 phalanges, as well as numerous muscles innervated by the median and ulnar nerves. Hand: Anatomy and applies varus pressure on the ankle. 
    • The test is positive if there is lateral compartment gaping. 
  • External rotation External Rotation Examination of the Upper Limbs recurvatum test: 
    • The patient lies supine with the affected knee extended.
    • The clinician Clinician A physician, nurse practitioner, physician assistant, or another health professional who is directly involved in patient care and has a professional relationship with patients. Clinician–Patient Relationship stabilizes the distal femur with 1 hand Hand The hand constitutes the distal part of the upper limb and provides the fine, precise movements needed in activities of daily living. It consists of 5 metacarpal bones and 14 phalanges, as well as numerous muscles innervated by the median and ulnar nerves. Hand: Anatomy and externally rotates the tibia Tibia The second longest bone of the skeleton. It is located on the medial side of the lower leg, articulating with the fibula laterally, the talus distally, and the femur proximally. Knee Joint: Anatomy.
    • Positive test: hyperextension of the knee
• Grades of instability in LCL injuries:
  • Grade I:
    • Clinical signs of sprain ( pain Pain An unpleasant sensation induced by noxious stimuli which are detected by nerve endings of nociceptive neurons. Pain: Types and Pathways)
    • No instability
  • Grade II:
    • More signs of sprain ( pain Pain An unpleasant sensation induced by noxious stimuli which are detected by nerve endings of nociceptive neurons. Pain: Types and Pathways and edema Edema Edema is a condition in which excess serous fluid accumulates in the body cavity or interstitial space of connective tissues. Edema is a symptom observed in several medical conditions. It can be categorized into 2 types, namely, peripheral (in the extremities) and internal (in an organ or body cavity). Edema)
    • Ligament laxity is observed, but with an end point.
  • Grade III:
    • Severe clinical signs of sprain ( pain Pain An unpleasant sensation induced by noxious stimuli which are detected by nerve endings of nociceptive neurons. Pain: Types and Pathways, edema Edema Edema is a condition in which excess serous fluid accumulates in the body cavity or interstitial space of connective tissues. Edema is a symptom observed in several medical conditions. It can be categorized into 2 types, namely, peripheral (in the extremities) and internal (in an organ or body cavity). Edema, ecchymosis Ecchymosis Extravasation of blood into the skin, resulting in a nonelevated, rounded or irregular, blue or purplish patch, larger than a petechia. Orbital Fractures)
    • Noticeable knee instability

Diagnosis

Diagnosis is made clinically and confirmed by imaging studies.

• Bedside ultrasonography Bedside Ultrasonography ACES and RUSH: Resuscitation Ultrasound Protocols in minor LCL injuries
• X-ray X-ray Penetrating electromagnetic radiation emitted when the inner orbital electrons of an atom are excited and release radiant energy. X-ray wavelengths range from 1 pm to 10 nm. Hard x-rays are the higher energy, shorter wavelength x-rays. Soft x-rays or grenz rays are less energetic and longer in wavelength. The short wavelength end of the x-ray spectrum overlaps the gamma rays wavelength range. The distinction between gamma rays and x-rays is based on their radiation source. Pulmonary Function Tests is useful only to rule out fractures.
• MRI indicated if:
  • History of significant trauma 
  • Ultrasound findings suggest major injury to the LCL and other structures:
    • Cruciate ligament
    • Meniscal tear

Management

• Conservative management for grade I and II injuries:
  • RICE
  • No weight-bearing (use crutches or wheelchair)
  • NSAIDs NSAIDS Primary vs Secondary Headaches for pain Pain An unpleasant sensation induced by noxious stimuli which are detected by nerve endings of nociceptive neurons. Pain: Types and Pathways relief
  • Bracing for 3–6 weeks
• Orthopedic surgery consultation and surgical management:
  • Consultation in all cases to discuss treatment options
  • Surgery is indicated in grade III injuries.
  • Caution to avoid injury to the common peroneal nerve Peroneal nerve The lateral of the two terminal branches of the sciatic nerve. The peroneal (or fibular) nerve provides motor and sensory innervation to parts of the leg and foot. Popliteal Fossa: Anatomy and neurologic complications
• Rehabilitation with physical therapy Physical Therapy Becker Muscular Dystrophy 6 weeks after grade I and II injuries:
  • Joint instability and pain Pain An unpleasant sensation induced by noxious stimuli which are detected by nerve endings of nociceptive neurons. Pain: Types and Pathways must be resolved and range of motion Range of motion The distance and direction to which a bone joint can be extended. Range of motion is a function of the condition of the joints, muscles, and connective tissues involved. Joint flexibility can be improved through appropriate muscle strength exercises. Examination of the Upper Limbs restored.
  • Grade I: return to activity after 4 weeks
  • Grade II: return to activity after 10 weeks
• Grade III injuries: immobilization Immobilization Delirium and non–weight-bearing for 6 weeks postoperatively
  • Rehabilitation starts 4 months after reconstruction. 
  • Criteria for return to full activity:
    • Fully restored range of motion Range of motion The distance and direction to which a bone joint can be extended. Range of motion is a function of the condition of the joints, muscles, and connective tissues involved. Joint flexibility can be improved through appropriate muscle strength exercises. Examination of the Upper Limbs 
    • Recovered quadriceps and hamstring strength
    • Resolution of joint pain Pain An unpleasant sensation induced by noxious stimuli which are detected by nerve endings of nociceptive neurons. Pain: Types and Pathways
    • Resolution of joint laxity and instability
    • Able to complete normal physical activities without pain Pain An unpleasant sensation induced by noxious stimuli which are detected by nerve endings of nociceptive neurons. Pain: Types and Pathways
• Complications:
  • Chronic knee pain Pain An unpleasant sensation induced by noxious stimuli which are detected by nerve endings of nociceptive neurons. Pain: Types and Pathways
  • Knee instability
  • Neurologic, due to common peroneal nerve injury Nerve Injury Surgical Complications:
    • Long-term foot drop Foot Drop Leprosy
    • Lower limb weakness
    • Decreased sensation
• Prognosis Prognosis A prediction of the probable outcome of a disease based on a individual’s condition and the usual course of the disease as seen in similar situations. Non-Hodgkin Lymphomas: The majority of patients Patients Individuals participating in the health care system for the purpose of receiving therapeutic, diagnostic, or preventive procedures. Clinician–Patient Relationship return to normal functioning after treatment.

Differential diagnosis of LCL tear

• Posterior knee dislocation Posterior Knee Dislocation Knee Dislocation: pathologic loss of articulation of the knee joint Knee joint The knee joint is made up of the articulations between the femur, tibia, and patella bones, and is one of the largest and most complex joints of the human body. The knee is classified as a synovial hinge joint, which primarily allows for flexion and extension with a more limited degree of translation and rotation. Knee Joint: Anatomy due to high-energy trauma such as that due to motor-vehicle collisions or low-energy trauma Low-Energy Trauma Toddler’s Fractures such as that seen in athletic training. 
• Meniscal tear: injury to the meniscus caused by rotational or shearing forces Shearing forces Vascular Resistance, Flow, and Mean Arterial Pressure across the tibiofemoral joint Tibiofemoral joint Knee Joint: Anatomy. Clinical presentation includes a history of a twisting or rotational injury followed by joint line pain Pain An unpleasant sensation induced by noxious stimuli which are detected by nerve endings of nociceptive neurons. Pain: Types and Pathways associated with a small effusion. Some patients Patients Individuals participating in the health care system for the purpose of receiving therapeutic, diagnostic, or preventive procedures. Clinician–Patient Relationship may also present with mechanical symptoms, such as joint locking, clicking, or catching.
• ACL ACL A strong ligament of the knee that originates from the posteromedial portion of the lateral condyle of the femur, passes anteriorly and inferiorly between the condyles, and attaches to the depression in front of the intercondylar eminence of the tibia. Knee Joint: Anatomy injury: causes structural damage to the ligament whose functions are to control anterior translation Translation Translation is the process of synthesizing a protein from a messenger RNA (mRNA) transcript. This process is divided into three primary stages: initiation, elongation, and termination. Translation is catalyzed by structures known as ribosomes, which are large complexes of proteins and ribosomal RNA (rRNA). Stages and Regulation of Translation of the tibia Tibia The second longest bone of the skeleton. It is located on the medial side of the lower leg, articulating with the fibula laterally, the talus distally, and the femur proximally. Knee Joint: Anatomy and restrain tibial rotation Rotation Motion of an object in which either one or more points on a line are fixed. It is also the motion of a particle about a fixed point. X-rays and varus/valgus stress.

Posterior Cruciate Ligament (PCL) Injury

Definition

The posterior cruciate ligament Posterior Cruciate Ligament A strong ligament of the knee that originates from the anterolateral surface of the medial condyle of the femur, passes posteriorly and inferiorly between the condyles, and attaches to the posterior intercondylar area of the tibia. Knee Joint: Anatomy ( PCL PCL A strong ligament of the knee that originates from the anterolateral surface of the medial condyle of the femur, passes posteriorly and inferiorly between the condyles, and attaches to the posterior intercondylar area of the tibia. Knee Joint: Anatomy) is the largest and strongest ligament in the knee. Injury to the PCL PCL A strong ligament of the knee that originates from the anterolateral surface of the medial condyle of the femur, passes posteriorly and inferiorly between the condyles, and attaches to the posterior intercondylar area of the tibia. Knee Joint: Anatomy causes structural damage resulting in loss of stabilization with resultant posterior translation Translation Translation is the process of synthesizing a protein from a messenger RNA (mRNA) transcript. This process is divided into three primary stages: initiation, elongation, and termination. Translation is catalyzed by structures known as ribosomes, which are large complexes of proteins and ribosomal RNA (rRNA). Stages and Regulation of Translation of the tibia Tibia The second longest bone of the skeleton. It is located on the medial side of the lower leg, articulating with the fibula laterally, the talus distally, and the femur proximally. Knee Joint: Anatomy.

Epidemiology

• Seen in approximately 3% of knee injuries due to trauma
• 95% of PCL PCL A strong ligament of the knee that originates from the anterolateral surface of the medial condyle of the femur, passes posteriorly and inferiorly between the condyles, and attaches to the posterior intercondylar area of the tibia. Knee Joint: Anatomy tears occur in combination with other ligament tears; isolated PCL PCL A strong ligament of the knee that originates from the anterolateral surface of the medial condyle of the femur, passes posteriorly and inferiorly between the condyles, and attaches to the posterior intercondylar area of the tibia. Knee Joint: Anatomy injuries are uncommon.

Etiology

• High-energy trauma such as motor-vehicle accidents, in association with damage to other knee structures
• Sports injuries: 2nd most common cause of PCL PCL A strong ligament of the knee that originates from the anterolateral surface of the medial condyle of the femur, passes posteriorly and inferiorly between the condyles, and attaches to the posterior intercondylar area of the tibia. Knee Joint: Anatomy injury

Clinical presentation

Isolated PCL PCL A strong ligament of the knee that originates from the anterolateral surface of the medial condyle of the femur, passes posteriorly and inferiorly between the condyles, and attaches to the posterior intercondylar area of the tibia. Knee Joint: Anatomy injuries are relatively uncommon, and athletes with such injuries may continue to function at a high level.

History:

• Pain Pain An unpleasant sensation induced by noxious stimuli which are detected by nerve endings of nociceptive neurons. Pain: Types and Pathways in the back of the knee (especially with squatting or kneeling)
• Slight limp 
• Chronically injured PCL-deficient knee may present with generalized anterior knee pain Pain An unpleasant sensation induced by noxious stimuli which are detected by nerve endings of nociceptive neurons. Pain: Types and Pathways localized to the medial compartment or patellofemoral joint Patellofemoral Joint The articulation between the articular surface of the patella and the patellar surface of the femur. Knee Joint: Anatomy.

Physical examination: 

• Mild to moderate knee effusion
• Loss of terminal knee flexion Flexion Examination of the Upper Limbs (final 10–20 degrees)
• Posterior drawer test:
  • The patient lies supine with the affected knee at a 90-degree angle. 
  • The clinician Clinician A physician, nurse practitioner, physician assistant, or another health professional who is directly involved in patient care and has a professional relationship with patients. Clinician–Patient Relationship stabilizes the leg Leg The lower leg, or just “leg” in anatomical terms, is the part of the lower limb between the knee and the ankle joint. The bony structure is composed of the tibia and fibula bones, and the muscles of the leg are grouped into the anterior, lateral, and posterior compartments by extensions of fascia. Leg: Anatomy by sitting on the patient’s toes and grasps the proximal lower leg Leg The lower leg, or just “leg” in anatomical terms, is the part of the lower limb between the knee and the ankle joint. The bony structure is composed of the tibia and fibula bones, and the muscles of the leg are grouped into the anterior, lateral, and posterior compartments by extensions of fascia. Leg: Anatomy at the upper tibia Tibia The second longest bone of the skeleton. It is located on the medial side of the lower leg, articulating with the fibula laterally, the talus distally, and the femur proximally. Knee Joint: Anatomy and tries to displace the lower leg Leg The lower leg, or just “leg” in anatomical terms, is the part of the lower limb between the knee and the ankle joint. The bony structure is composed of the tibia and fibula bones, and the muscles of the leg are grouped into the anterior, lateral, and posterior compartments by extensions of fascia. Leg: Anatomy posteriorly. 
  • Positive test: excessive posterior translation Translation Translation is the process of synthesizing a protein from a messenger RNA (mRNA) transcript. This process is divided into three primary stages: initiation, elongation, and termination. Translation is catalyzed by structures known as ribosomes, which are large complexes of proteins and ribosomal RNA (rRNA). Stages and Regulation of Translation
• Muller’s test, also called the quadriceps active test:
  • The patient lies supine as above and is asked to raise the foot Foot The foot is the terminal portion of the lower limb, whose primary function is to bear weight and facilitate locomotion. The foot comprises 26 bones, including the tarsal bones, metatarsal bones, and phalanges. The bones of the foot form longitudinal and transverse arches and are supported by various muscles, ligaments, and tendons. Foot: Anatomy off the table.
  • Positive test: anterior translation Translation Translation is the process of synthesizing a protein from a messenger RNA (mRNA) transcript. This process is divided into three primary stages: initiation, elongation, and termination. Translation is catalyzed by structures known as ribosomes, which are large complexes of proteins and ribosomal RNA (rRNA). Stages and Regulation of Translation of the proximal tibia Tibia The second longest bone of the skeleton. It is located on the medial side of the lower leg, articulating with the fibula laterally, the talus distally, and the femur proximally. Knee Joint: Anatomy prior to the foot Foot The foot is the terminal portion of the lower limb, whose primary function is to bear weight and facilitate locomotion. The foot comprises 26 bones, including the tarsal bones, metatarsal bones, and phalanges. The bones of the foot form longitudinal and transverse arches and are supported by various muscles, ligaments, and tendons. Foot: Anatomy leaving the table while attempting to elevate the foot Foot The foot is the terminal portion of the lower limb, whose primary function is to bear weight and facilitate locomotion. The foot comprises 26 bones, including the tarsal bones, metatarsal bones, and phalanges. The bones of the foot form longitudinal and transverse arches and are supported by various muscles, ligaments, and tendons. Foot: Anatomy

Diagnosis

• X-ray X-ray Penetrating electromagnetic radiation emitted when the inner orbital electrons of an atom are excited and release radiant energy. X-ray wavelengths range from 1 pm to 10 nm. Hard x-rays are the higher energy, shorter wavelength x-rays. Soft x-rays or grenz rays are less energetic and longer in wavelength. The short wavelength end of the x-ray spectrum overlaps the gamma rays wavelength range. The distinction between gamma rays and x-rays is based on their radiation source. Pulmonary Function Tests to rule out fractures
• MRI for suspected PCL PCL A strong ligament of the knee that originates from the anterolateral surface of the medial condyle of the femur, passes posteriorly and inferiorly between the condyles, and attaches to the posterior intercondylar area of the tibia. Knee Joint: Anatomy injury

Management

Referral to orthopedic surgeon is needed.

• Grade III PCL PCL A strong ligament of the knee that originates from the anterolateral surface of the medial condyle of the femur, passes posteriorly and inferiorly between the condyles, and attaches to the posterior intercondylar area of the tibia. Knee Joint: Anatomy injuries: demonstrated by the anterior border of the medial tibial plateau Plateau Cardiac Physiology being displaced posteriorly > 10 mm
• Additional significant soft tissue Soft Tissue Soft Tissue Abscess injuries 
• PCL PCL A strong ligament of the knee that originates from the anterolateral surface of the medial condyle of the femur, passes posteriorly and inferiorly between the condyles, and attaches to the posterior intercondylar area of the tibia. Knee Joint: Anatomy disruption involving avulsion fracture Avulsion fracture Tearing away of the cortical bone fragment at the location of a strong ligament or tendon attachment. The bone fragment detachment site often occurs near a soft site (e.g., growth plate) at the base where ligaments; tendons; or joint capsules attach. Overview of Bone Fractures at the ligamentous insertion at the tibia Tibia The second longest bone of the skeleton. It is located on the medial side of the lower leg, articulating with the fibula laterally, the talus distally, and the femur proximally. Knee Joint: Anatomy
• Isolated PCL PCL A strong ligament of the knee that originates from the anterolateral surface of the medial condyle of the femur, passes posteriorly and inferiorly between the condyles, and attaches to the posterior intercondylar area of the tibia. Knee Joint: Anatomy injuries, as multiligament trauma typically requires surgical intervention. 

Differential diagnosis of PCL tear PCL tear Knee Pain

• Posterior collateral ligament injury: Other injuries are often sustained in combination with PCL PCL A strong ligament of the knee that originates from the anterolateral surface of the medial condyle of the femur, passes posteriorly and inferiorly between the condyles, and attaches to the posterior intercondylar area of the tibia. Knee Joint: Anatomy injury.
• Proximal tibial fracture Fracture A fracture is a disruption of the cortex of any bone and periosteum and is commonly due to mechanical stress after an injury or accident. Open fractures due to trauma can be a medical emergency. Fractures are frequently associated with automobile accidents, workplace injuries, and trauma. Overview of Bone Fractures: may result from similar injuries causing a PCL tear PCL tear Knee Pain. A tibial fracture Fracture A fracture is a disruption of the cortex of any bone and periosteum and is commonly due to mechanical stress after an injury or accident. Open fractures due to trauma can be a medical emergency. Fractures are frequently associated with automobile accidents, workplace injuries, and trauma. Overview of Bone Fractures typically presents clinically with a hemarthrosis Hemarthrosis Bleeding into the joints. It may arise from trauma or spontaneously in patients with hemophilia. Hemophilia, larger than the effusion seen with a PCL PCL A strong ligament of the knee that originates from the anterolateral surface of the medial condyle of the femur, passes posteriorly and inferiorly between the condyles, and attaches to the posterior intercondylar area of the tibia. Knee Joint: Anatomy injury. There is associated pain Pain An unpleasant sensation induced by noxious stimuli which are detected by nerve endings of nociceptive neurons. Pain: Types and Pathways and guarding that limit Limit A value (e.g., pressure or time) that should not be exceeded and which is specified by the operator to protect the lung Invasive Mechanical Ventilation clinical examination. Diagnosis is made with X-ray X-ray Penetrating electromagnetic radiation emitted when the inner orbital electrons of an atom are excited and release radiant energy. X-ray wavelengths range from 1 pm to 10 nm. Hard x-rays are the higher energy, shorter wavelength x-rays. Soft x-rays or grenz rays are less energetic and longer in wavelength. The short wavelength end of the x-ray spectrum overlaps the gamma rays wavelength range. The distinction between gamma rays and x-rays is based on their radiation source. Pulmonary Function Tests, and management is by an orthopedic specialist.
• Tibiofemoral dislocation: may occur following significant trauma and is a potentially limb-threatening injury if there is circulatory compromise. Tibiofemoral dislocation requires emergency evaluation. Clinical presentation is with severe pain Pain An unpleasant sensation induced by noxious stimuli which are detected by nerve endings of nociceptive neurons. Pain: Types and Pathways and swelling Swelling Inflammation and gross instability of the knee. There may be obvious deformity Deformity Examination of the Upper Limbs, and management is an urgent reduction if the dislocation does not reduce spontaneously.
• Bone Bone Bone is a compact type of hardened connective tissue composed of bone cells, membranes, an extracellular mineralized matrix, and central bone marrow. The 2 primary types of bone are compact and spongy. Bones: Structure and Types contusion: may occur at the same time as PCL PCL A strong ligament of the knee that originates from the anterolateral surface of the medial condyle of the femur, passes posteriorly and inferiorly between the condyles, and attaches to the posterior intercondylar area of the tibia. Knee Joint: Anatomy injury; however, posterior drawer test would be negative in a patient with an isolated bone Bone Bone is a compact type of hardened connective tissue composed of bone cells, membranes, an extracellular mineralized matrix, and central bone marrow. The 2 primary types of bone are compact and spongy. Bones: Structure and Types contusion.
• Quadriceps tendon Quadriceps tendon Knee Joint: Anatomy and patellar tendon tears: also may occur due to an injury involving falling with the knee flexed. With tendon tears, patients Patients Individuals participating in the health care system for the purpose of receiving therapeutic, diagnostic, or preventive procedures. Clinician–Patient Relationship often report feeling a popping sensation in the knee and are immediately unable to bear weight, whereas patients Patients Individuals participating in the health care system for the purpose of receiving therapeutic, diagnostic, or preventive procedures. Clinician–Patient Relationship with a PCL PCL A strong ligament of the knee that originates from the anterolateral surface of the medial condyle of the femur, passes posteriorly and inferiorly between the condyles, and attaches to the posterior intercondylar area of the tibia. Knee Joint: Anatomy injury usually can bear weight. On X-ray X-ray Penetrating electromagnetic radiation emitted when the inner orbital electrons of an atom are excited and release radiant energy. X-ray wavelengths range from 1 pm to 10 nm. Hard x-rays are the higher energy, shorter wavelength x-rays. Soft x-rays or grenz rays are less energetic and longer in wavelength. The short wavelength end of the x-ray spectrum overlaps the gamma rays wavelength range. The distinction between gamma rays and x-rays is based on their radiation source. Pulmonary Function Tests, patients Patients Individuals participating in the health care system for the purpose of receiving therapeutic, diagnostic, or preventive procedures. Clinician–Patient Relationship with tendon tears may have altered height of the patella Patella The flat, triangular bone situated at the anterior part of the knee. Knee Joint: Anatomy or signs of a patellar avulsion injury.