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Knee Dislocation

Knee Dislocation

A dislocation of the knee ( tibiofemoral joint Tibiofemoral joint Knee Joint: Anatomy) is a rare injury but is important to recognize because of limb-threatening trauma. Knee dislocations (KDs) are emergent cases that require immediate reduction and evaluation of the neurovascular system. Clinical presentation Presentation The position or orientation of the fetus at near term or during obstetric labor, determined by its relation to the spine of the mother and the birth canal. The normal position is a vertical, cephalic presentation with the fetal vertex flexed on the neck. Normal and Abnormal Labor includes precedent trauma, obvious deformity Deformity Examination of the Upper Limbs, effusion, 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, and possible signs of vascular injury to the popliteal artery Popliteal Artery The continuation of the femoral artery coursing through the popliteal fossa; it divides into the anterior and posterior tibial arteries. Popliteal Fossa: Anatomy. Management includes reduction of the dislocation, serial examinations for arterial perfusion, imaging of the vascular system, and orthopedic and vascular consultations.

Last updated: 29 Apr, 2022

Editorial responsibility: Stanley Oiseth, Lindsay Jones, Evelin Maza

Contents

Overview

Definition

A dislocation of the knee ( tibiofemoral joint Tibiofemoral joint Knee Joint: Anatomy) is a rare injury that is important to recognize due to the frequent association with vascular injury and associated risk of limb amputation Amputation An amputation is the separation of a portion of the limb or the entire limb from the body, along with the bone. Amputations are generally indicated for conditions that compromise the viability of the limb or promote the spread of a local process that could manifest systemically. Amputation. These are emergent cases that require immediate reduction and evaluation of the neurovascular system.

Epidemiology

  • 0.02% of all musculoskeletal injuries (very uncommon)
  • 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 may be higher, as the actual percentage of cases that dislocate and spontaneously reduce is unknown.
  • 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 is an independent risk factor.
  • High-velocity dislocations are more commonly associated with vascular injury.
  • Vascular injuries reported in approximately 5%–50% of patients Patients Individuals participating in the health care system for the purpose of receiving therapeutic, diagnostic, or preventive procedures. Clinician–Patient Relationship
  • 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 injuries reported in approximately 20% of patients Patients Individuals participating in the health care system for the purpose of receiving therapeutic, diagnostic, or preventive procedures. Clinician–Patient Relationship

Etiology

  • High-velocity or high-energy trauma:
  • Low-velocity trauma: associated with morbid 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

Classification

Knee dislocations (KDs) can be classified based on the position 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 in relation to the femur, etiology, or on the pattern of ligament tears (Schenck classification).

Classification based on the position 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 in relation to the femur:

  • Types:
    • Anterior dislocation
    • Posterior dislocation
    • Medial dislocation
    • Lateral dislocation
    • Rotatory dislocation
  • Posterior and anterior KDs: most common, highest risk of associated popliteal artery Popliteal Artery The continuation of the femoral artery coursing through the popliteal fossa; it divides into the anterior and posterior tibial arteries. Popliteal Fossa: Anatomy injury
  • Posterior dislocations: primarily occur secondary to direct trauma Direct Trauma Toddler’s Fractures to the anterior 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 of a flexed knee (dashboard injury)
Image showcasing the bony landmarks of the femur, tibia, and patella bones. Anterior surface

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: bony structure and landmarks

Image by BioDigital, edited by Lecturio

Classification by etiology:

  • High velocity: 
    • Most common mechanism
    • High-velocity impact or trauma
  • Low velocity:
    • Lower-velocity injuries/falls
    • Associated with morbid 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

Schenck classification of KDs: based on pattern of ligament tears

Usually a high-energy mechanism of injury is required for multiple ligaments to fail in order for dislocation to occur.

  • KD KD An acute, febrile, mucocutaneous condition accompanied by swelling of cervical lymph nodes in infants and young children. The principal symptoms are fever, congestion of the ocular conjunctivae, reddening of the lips and oral cavity, protuberance of tongue papillae, and edema or erythema of the extremities. Kawasaki Disease I: involvement of 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 ( 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) or 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)
  • KD KD An acute, febrile, mucocutaneous condition accompanied by swelling of cervical lymph nodes in infants and young children. The principal symptoms are fever, congestion of the ocular conjunctivae, reddening of the lips and oral cavity, protuberance of tongue papillae, and edema or erythema of the extremities. Kawasaki Disease II: injury to both 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/ 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 with both collaterals intact (rare)
  • KD KD An acute, febrile, mucocutaneous condition accompanied by swelling of cervical lymph nodes in infants and young children. The principal symptoms are fever, congestion of the ocular conjunctivae, reddening of the lips and oral cavity, protuberance of tongue papillae, and edema or erythema of the extremities. Kawasaki Disease III: injury to 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 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 and either medial collateral ligament Medial collateral ligament Knee Joint: Anatomy ( MCL MCL Knee Joint: Anatomy) or lateral collateral ligament Lateral collateral ligament Knee Joint: Anatomy (LCL) (not both)
    • KD KD An acute, febrile, mucocutaneous condition accompanied by swelling of cervical lymph nodes in infants and young children. The principal symptoms are fever, congestion of the ocular conjunctivae, reddening of the lips and oral cavity, protuberance of tongue papillae, and edema or erythema of the extremities. Kawasaki Disease IIIM: MCL MCL Knee Joint: Anatomy torn
    • KD KD An acute, febrile, mucocutaneous condition accompanied by swelling of cervical lymph nodes in infants and young children. The principal symptoms are fever, congestion of the ocular conjunctivae, reddening of the lips and oral cavity, protuberance of tongue papillae, and edema or erythema of the extremities. Kawasaki Disease IIIL: LCL torn
  • KD KD An acute, febrile, mucocutaneous condition accompanied by swelling of cervical lymph nodes in infants and young children. The principal symptoms are fever, congestion of the ocular conjunctivae, reddening of the lips and oral cavity, protuberance of tongue papillae, and edema or erythema of the extremities. Kawasaki Disease IV: all 4 ligaments torn ( 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, 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, MCL MCL Knee Joint: Anatomy, LCL), highest rate of vascular injury
  • KD KD An acute, febrile, mucocutaneous condition accompanied by swelling of cervical lymph nodes in infants and young children. The principal symptoms are fever, congestion of the ocular conjunctivae, reddening of the lips and oral cavity, protuberance of tongue papillae, and edema or erythema of the extremities. Kawasaki Disease V: multiple ligamentous injuries with periarticular 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 (knee 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-dislocation)

Related videos

4:27
Posterior Knee Dislocation

Pathophysiology

Trauma mechanism

  • Posterior: 
    • Direct force to the anterior 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 the knee flexed at 90 degrees
    • Seen in motor vehicle accidents Motor Vehicle Accidents Spinal Cord Injuries: 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 striking the dashboard
  • Anterior: 
    • Hyperextension injury
    • Disruption of the posterior structures of the knee
  • Lateral: 
    • Varus/valgus stress
    • Commonly associated with a tibial plateau Plateau Cardiac Physiology 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
    • Associated with peroneal nerve injury Nerve Injury Surgical Complications
  • Medial:
    • Varus/valgus stress
    • Commonly associated with a tibial plateau Plateau Cardiac Physiology 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
  • Rotatory: 

Pathological anatomy

  • 2 or more ligaments (cruciate or collateral) must be compromised to allow the knee to dislocate.
  • Most commonly, both cruciate ligaments and at least 1 collateral ligament are disrupted.
  • The popliteal artery Popliteal Artery The continuation of the femoral artery coursing through the popliteal fossa; it divides into the anterior and posterior tibial arteries. Popliteal Fossa: Anatomy:
    • Traverses the posterior portion of the knee
    • Attaches proximally at the adductor hiatus
    • Attaches distally to the proximal arch of the soleus Soleus Leg: Anatomy muscle
    • This tethering makes it vulnerable to injury with a KD KD An acute, febrile, mucocutaneous condition accompanied by swelling of cervical lymph nodes in infants and young children. The principal symptoms are fever, congestion of the ocular conjunctivae, reddening of the lips and oral cavity, protuberance of tongue papillae, and edema or erythema of the extremities. Kawasaki Disease.
  • The 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:
    • Winds laterally around the proximal fibula Fibula The bone of the lower leg lateral to and smaller than the tibia. In proportion to its length, it is the most slender of the long bones. Leg: Anatomy
    • Tethered above and below the femoral head by fascial/ligamentous structures
    • This tethering makes it vulnerable to injury with a KD KD An acute, febrile, mucocutaneous condition accompanied by swelling of cervical lymph nodes in infants and young children. The principal symptoms are fever, congestion of the ocular conjunctivae, reddening of the lips and oral cavity, protuberance of tongue papillae, and edema or erythema of the extremities. Kawasaki Disease.
  • KDs can be open or closed.
  • Posterolateral dislocations are generally irreducible and require surgical management.
Menisci and articular surfaces of the knee

Image displaying the menisci Menisci Meniscus Tear, ligaments, and bony surfaces and their relation to one another

Image by Lecturio. License: CC BY-NC-SA 4.0
Image displaying the menisci and their relation with other articular surfaces that compose the knee joint

Image displaying the menisci Menisci Meniscus Tear and their relation with other articular surfaces that compose 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

Image by BioDigital, edited by Lecturio
Supporting ligaments of the patellofemoral joint

Supporting ligaments of the patellofemoral joint Patellofemoral Joint The articulation between the articular surface of the patella and the patellar surface of the femur. Knee Joint: Anatomy

Image by Lecturio. License: CC BY-NC-SA 4.0
Contents of the popliteal fossa

Posterior anatomy of the knee showing the relationship Relationship A connection, association, or involvement between 2 or more parties. Clinician–Patient Relationship between the popliteal artery Popliteal Artery The continuation of the femoral artery coursing through the popliteal fossa; it divides into the anterior and posterior tibial arteries. Popliteal Fossa: Anatomy and the tibial and common fibular nerves

Image by BioDigital, edited by Lecturio

Clinical Presentation

Knee dislocations are an uncommon injury but require emergent evaluation and management secondary to the possibility of limb ischemia Ischemia A hypoperfusion of the blood through an organ or tissue caused by a pathologic constriction or obstruction of its blood vessels, or an absence of blood circulation. Ischemic Cell Damage, which may require surgical intervention to avoid  amputation Amputation An amputation is the separation of a portion of the limb or the entire limb from the body, along with the bone. Amputations are generally indicated for conditions that compromise the viability of the limb or promote the spread of a local process that could manifest systemically. Amputation.

Important considerations

  • If dislocation occurred in the context of high-energy trauma: Patients Patients Individuals participating in the health care system for the purpose of receiving therapeutic, diagnostic, or preventive procedures. Clinician–Patient Relationship may require simultaneous evaluation and management following the advanced trauma life support (ATLS) method.
  • Consider the possibility of spontaneous reductions: In the absence of obvious deformity Deformity Examination of the Upper Limbs, 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 may overlook the high risk of an associated vascular injury.

History

  • In isolated trauma, the patient may be able to describe the mechanism. 
  • Patients Patients Individuals participating in the health care system for the purpose of receiving therapeutic, diagnostic, or preventive procedures. Clinician–Patient Relationship or first responders will usually report a high-energy blunt trauma (e.g., motor Motor Neurons which send impulses peripherally to activate muscles or secretory cells. Nervous System: Histology vehicle accident, industrial accident, sports injury).
  • As these injuries are often high-energy trauma, evaluation for other life-threatening injuries is essential.

Physical examination

  • Obvious deformity Deformity Examination of the Upper Limbs of the knee:
    • Associated swelling Swelling Inflammation
    • Limited 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
    • Appearance less dramatic in morbidly obese patients Patients Individuals participating in the health care system for the purpose of receiving therapeutic, diagnostic, or preventive procedures. Clinician–Patient Relationship
    • Up to 50% of KDs may have spontaneously reduced prior to presentation Presentation The position or orientation of the fetus at near term or during obstetric labor, determined by its relation to the spine of the mother and the birth canal. The normal position is a vertical, cephalic presentation with the fetal vertex flexed on the neck. Normal and Abnormal Labor (exact percentage is unknown).
  • Meticulous vascular examination:
    • Popliteal artery Popliteal Artery The continuation of the femoral artery coursing through the popliteal fossa; it divides into the anterior and posterior tibial arteries. Popliteal Fossa: Anatomy injury:
      • Decreased distal pulses (always check distal pulses and perfusion)
      • Ankle-brachial index Ankle-brachial index Comparison of the blood pressure between the brachial artery and the posterior tibial artery. It is a predictor of peripheral arterial disease. Cardiovascular Examination < 0.9
      • Compare to contralateral limb.
    • Signs of severe vascular compromise: 
      • Absent pulses
      • Pale or cool extremity
      • Paresthesias Paresthesias Subjective cutaneous sensations (e.g., cold, warmth, tingling, pressure, etc.) that are experienced spontaneously in the absence of stimulation. Posterior Cord Syndrome
      • Paralysis 
      • Palpable thrill or audible bruit
      • Visible expanding hematoma Hematoma A collection of blood outside the blood vessels. Hematoma can be localized in an organ, space, or tissue. Intussusception
  • Neurological examination Neurological examination A neurological exam is a systematic assessment of cognitive, sensory, and motor responses to identify pathologies of the nervous system. A neurological exam allows for the localization of neurologic lesions to narrow the differential diagnosis and focus on subsequent laboratory and imaging examinations. The exam should include assessments of the subject’s mental status, speech, cranial nerves, motor system, deep tendon reflexes, sensation, balance, and coordination. Neurological Examination:
    • Peroneal nerve injury Nerve Injury Surgical Complications common with KD KD An acute, febrile, mucocutaneous condition accompanied by swelling of cervical lymph nodes in infants and young children. The principal symptoms are fever, congestion of the ocular conjunctivae, reddening of the lips and oral cavity, protuberance of tongue papillae, and edema or erythema of the extremities. Kawasaki Disease
    • 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 exam: 
      • Evaluate sensation: 1st web space 
      • Evaluate motor Motor Neurons which send impulses peripherally to activate muscles or secretory cells. Nervous System: Histology involvement: eversion Eversion Chronic Apophyseal Injury of 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 and 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/toe dorsiflexion
      • No associated deep tendon reflex
  • Ligamentous examination:
    • Evaluate ligamentous integrity of the knee after neurovascular integrity.
    • Rule out associated 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 in high-energy trauma prior to ligament evaluation.
    • Evidence of multiple ligamentous disruption in the appropriate clinical scenario may indicate a KD KD An acute, febrile, mucocutaneous condition accompanied by swelling of cervical lymph nodes in infants and young children. The principal symptoms are fever, congestion of the ocular conjunctivae, reddening of the lips and oral cavity, protuberance of tongue papillae, and edema or erythema of the extremities. Kawasaki Disease with a spontaneous reduction.
Neglected irreducible posterolateral knee dislocation

Posterior knee dislocation: Note the obvious deformity Deformity Examination of the Upper Limbs as 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 is displaced downward due to gravity.

Image: “Neglected irreducible posterolateral knee dislocation” by Department of Orthopaedics, Postgraduate Institute of Medical Education Medical education Conflict of Interest and Research Research Critical and exhaustive investigation or experimentation, having for its aim the discovery of new facts and their correct interpretation, the revision of accepted conclusions, theories, or laws in the light of newly discovered facts, or the practical application of such new or revised conclusions, theories, or laws. Conflict of Interest, Sector 12, Chandigarh – 160 012, India. License: CC BY 2.0

Diagnosis

The majority of complete KDs are clinically obvious with a history of significant trauma and gross deformity Deformity Examination of the Upper Limbs of the knee. Diagnosis is made clinically, although imaging studies may be indicated to confirm suspected vascular injury or 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 and/or for surgical planning.

Steps

  • Determine the direction of the KD KD An acute, febrile, mucocutaneous condition accompanied by swelling of cervical lymph nodes in infants and young children. The principal symptoms are fever, congestion of the ocular conjunctivae, reddening of the lips and oral cavity, protuberance of tongue papillae, and edema or erythema of the extremities. Kawasaki Disease.
  • Consider potential dislocation with spontaneous reduction: 
    • Gross instability of the knee in the setting of trauma
    • Evidence of significant hyperextension of the knee in the setting of trauma
  • Imaging studies are indicated for evaluation of associated 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, ligamentous injury, and/or arterial injury Arterial Injury Hemothorax.

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

  • Plain X-rays X-rays X-rays are high-energy particles of electromagnetic radiation used in the medical field for the generation of anatomical images. X-rays are projected through the body of a patient and onto a film, and this technique is called conventional or projectional radiography. X-rays: indicated post-reduction or prior to any ligamentous evaluation
  • Anteroposterior (AP) and lateral projections of the knee: ideal to visualize the dislocation
Posterior knee dislocation on x-ray

Posterior knee dislocation seen on radiography before and after reduction with underlying knee 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

Image: “Posterior knee dislocation 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” by Department of Orthopaedics and Traumatology, Ankara Numune Training and Research Research Critical and exhaustive investigation or experimentation, having for its aim the discovery of new facts and their correct interpretation, the revision of accepted conclusions, theories, or laws in the light of newly discovered facts, or the practical application of such new or revised conclusions, theories, or laws. Conflict of Interest Hospital, 06100 Ankara, Turkey. License: CC BY 3.0

Vascular evaluation

  • Ankle-brachial indices evaluation:
    • Ankle-brachial index Ankle-brachial index Comparison of the blood pressure between the brachial artery and the posterior tibial artery. It is a predictor of peripheral arterial disease. Cardiovascular Examination < 0.9:
      • High 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 of vascular injury
      • Vascular imaging indicated
  • Duplex ultrasound:
    • Noninvasive alternative to direct angiography Angiography Radiography of blood vessels after injection of a contrast medium. Cardiac Surgery for vascular assessment
    • High sensitivity Sensitivity Binary classification measures to assess test results. Sensitivity or recall rate is the proportion of true positives. Blotting Techniques and specificity Specificity Specificity is the probability of correctly determining the absence of a condition. Immunoassays for clinically significant arterial injury Arterial Injury Hemothorax
    • Can be performed at bedside; does not require transport to CT scanner or angiography Angiography Radiography of blood vessels after injection of a contrast medium. Cardiac Surgery suite
    • Lowest cost
  • CT angiogram CT angiogram A non-invasive method that uses a ct scanner for capturing images of blood vessels and tissues. A contrast material is injected, which helps produce detailed images that aid in diagnosing vascular diseases. Pulmonary Function Tests:
    • Indicated in cases of asymmetric pulses, decreased ankle-brachial index Ankle-brachial index Comparison of the blood pressure between the brachial artery and the posterior tibial artery. It is a predictor of peripheral arterial disease. Cardiovascular Examination, or abnormal duplex ultrasound
    • Noninvasive alternative to direct arteriography 
    • Requires transport to CT scanner; does not require an angiography Angiography Radiography of blood vessels after injection of a contrast medium. Cardiac Surgery suite
    • Intermediate cost
  • Direct arteriography:
    • Criterion standard method of assessing vascular integrity
    • Formerly indicated for all KDs after reduction:
      • There is debate over the appropriate application of imaging options.
      • Some experts utilize advanced imaging in all instances of KD KD An acute, febrile, mucocutaneous condition accompanied by swelling of cervical lymph nodes in infants and young children. The principal symptoms are fever, congestion of the ocular conjunctivae, reddening of the lips and oral cavity, protuberance of tongue papillae, and edema or erythema of the extremities. Kawasaki Disease since vascular damage can go undetected. 
    • Risk of injury related to procedure (requires arterial puncture)
    • Requires interventional radiologist or vascular surgeon
    • Highest cost

Management

Closed reduction Closed Reduction Radial Head Subluxation (Nursemaid’s Elbow) of a KD KD An acute, febrile, mucocutaneous condition accompanied by swelling of cervical lymph nodes in infants and young children. The principal symptoms are fever, congestion of the ocular conjunctivae, reddening of the lips and oral cavity, protuberance of tongue papillae, and edema or erythema of the extremities. Kawasaki Disease should not be delayed, especially in a limb with obvious vascular impairment. As these injuries are often high-energy trauma, evaluation for other life-threatening injuries is essential.

Prompt reduction

  • Closed reduction Closed Reduction Radial Head Subluxation (Nursemaid’s Elbow) of the knee with procedural sedation
  • Reduction should not be delayed if the patient has any evidence for vascular compromise.
  • Procedure:
    • Longitudinal or axial Axial Computed Tomography (CT) traction followed by 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
    • Anterior and posterior dislocations usually reduce easily.
  • Immediate orthopedic consultation for dislocations that are not easily reduced
  • Posterolateral dislocations are generally irreducible; this may be indicated by a skin Skin The skin, also referred to as the integumentary system, is the largest organ of the body. The skin is primarily composed of the epidermis (outer layer) and dermis (deep layer). The epidermis is primarily composed of keratinocytes that undergo rapid turnover, while the dermis contains dense layers of connective tissue. Skin: Structure and Functions dimple in the anteromedial aspect of the knee. 
  • Immediate post-reduction evaluation of pulses and perfusion
  • Bedside X-rays X-rays X-rays are high-energy particles of electromagnetic radiation used in the medical field for the generation of anatomical images. X-rays are projected through the body of a patient and onto a film, and this technique is called conventional or projectional radiography. X-rays post-reduction to confirm reduction and evaluate for 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 
  • Advanced imaging indicated if suspected vascular compromise 
  • Immediate vascular consultation if any concerns for arterial injury Arterial Injury Hemothorax

Post reduction

  • Pulses and perfusion:
    • Immediate post-reduction evaluation of pulses and perfusion
    • Serial perfusion evaluations:
      • Presence of normal distal pulses alone does not rule out  popliteal artery Popliteal Artery The continuation of the femoral artery coursing through the popliteal fossa; it divides into the anterior and posterior tibial arteries. Popliteal Fossa: Anatomy injury.
      • Thrombus related to arterial injury Arterial Injury Hemothorax may present with delayed findings of poor perfusion.
      • Arterial-brachial index assessments
      • Bedside duplex ultrasonography Duplex ultrasonography Ultrasonography applying the doppler effect combined with real-time imaging. The real-time image is created by rapid movement of the ultrasound beam. A powerful advantage of this technique is the ability to estimate the velocity of flow from the doppler shift frequency. Hypercoagulable States
      • Patients Patients Individuals participating in the health care system for the purpose of receiving therapeutic, diagnostic, or preventive procedures. Clinician–Patient Relationship with any abnormalities on vascular exam, ankle-brachial index Ankle-brachial index Comparison of the blood pressure between the brachial artery and the posterior tibial artery. It is a predictor of peripheral arterial disease. Cardiovascular Examination, or duplex ultrasound: CT angiography CT angiography A non-invasive method that uses a ct scanner for capturing images of blood vessels and tissues. A contrast material is injected, which helps produce detailed images that aid in diagnosing vascular diseases. Imaging of the Lungs and Pleura or direct arteriography
  • Post-reduction imaging:
    • Bedside X-rays X-rays X-rays are high-energy particles of electromagnetic radiation used in the medical field for the generation of anatomical images. X-rays are projected through the body of a patient and onto a film, and this technique is called conventional or projectional radiography. X-rays post-reduction to confirm reduction and evaluate for 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
    • Advanced imaging indicated if suspected vascular compromise
  • Consultations:
    • Immediate vascular surgery Vascular surgery Vascular surgery is the specialized field of medicine that focuses on the surgical management of the pathologies of the peripheral circulation. The main goal of most vascular procedures is to restore circulatory function to the affected vessels by relieving occlusions or by redirecting blood flow (e.g., bypass). Vascular Surgery consultation for injuries with any signs or concerns of vascular compromise
    • Immediate orthopedic consultation:
      • Indicated for complicated reduction or irreducible reductions
      • Indicated for management of the fractures and/or ligamentous injury
Surgical repair of a knee dislocation

Operative repair of an irreducible posterolateral knee dislocation

Image: “Peroperative photograph” by Indian Journal of Orthopaedics. License: CC BY 4.0

Further management

  • Long 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 splint at 20–30 degrees of flexion Flexion Examination of the Upper Limbs
  • After initial management of acute injury, orthopedic management is related to the other specific structural injuries to the knee.

Complications

  • Injury to the popliteal artery Popliteal Artery The continuation of the femoral artery coursing through the popliteal fossa; it divides into the anterior and posterior tibial arteries. Popliteal Fossa: Anatomy or vein
  • Delayed arterial or venous thrombus formation
  • Peroneal nerve injury Nerve Injury Surgical Complications
  • Residual instability
  • Arthrofibrosis (stiffness): most common complication
  • Compartment syndrome Compartment Syndrome Compartment syndrome is a surgical emergency usually occurring secondary to trauma. The condition is marked by increased pressure within a compartment that compromises the circulation and function of the tissues within that space. Compartment Syndrome
  • Amputation Amputation An amputation is the separation of a portion of the limb or the entire limb from the body, along with the bone. Amputations are generally indicated for conditions that compromise the viability of the limb or promote the spread of a local process that could manifest systemically. Amputation

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

  • Depends on the velocity of the injury, neurovascular damage, and associated injuries
  • Athletes with a high-velocity injury are unlikely to return to pre-injury levels of sport.
  • Low-velocity dislocations have a relatively better 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.
  • 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 improves with timely repair of vascular injuries.

Clinical Relevance

  • 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: frequently injured, important stabilizing ligament of the knee. 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 is most commonly injured in sporting endeavors and frequently torn when the knee is dislocated. 
  • Meniscus tear Meniscus tear The menisci are fibrocartilaginous wedge-shaped structures between the distal femur and proximal tibia that stabilize and dissipate weight-bearing forces at the knee joint. A meniscus tear is an injury to the meniscus caused by rotational or shearing forces across the tibiofemoral joint. Meniscus Tear: injury to the meniscus occurs due to rotational or shearing forces Shearing forces Vascular Resistance, Flow, and Mean Arterial Pressure placed across 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. Meniscus tears may be associated with an ACL tear ACL tear Knee Pain and/or dislocation. 
  • Patellar instability and dislocation: a spectrum of conditions affecting the patella Patella The flat, triangular bone situated at the anterior part of the knee. Knee Joint: Anatomy secondary to trauma or activity. The conditions are characterized by peripatellar pain Pain An unpleasant sensation induced by noxious stimuli which are detected by nerve endings of nociceptive neurons. Pain: Types and Pathways and knee instability. With dislocation of the patella Patella The flat, triangular bone situated at the anterior part of the knee. Knee Joint: Anatomy, there may be obvious deformity Deformity Examination of the Upper Limbs and an inability to extend the knee.
  • Amputation Amputation An amputation is the separation of a portion of the limb or the entire limb from the body, along with the bone. Amputations are generally indicated for conditions that compromise the viability of the limb or promote the spread of a local process that could manifest systemically. Amputation: amputation Amputation An amputation is the separation of a portion of the limb or the entire limb from the body, along with the bone. Amputations are generally indicated for conditions that compromise the viability of the limb or promote the spread of a local process that could manifest systemically. Amputation may be required after prolonged ischemia Ischemia A hypoperfusion of the blood through an organ or tissue caused by a pathologic constriction or obstruction of its blood vessels, or an absence of blood circulation. Ischemic Cell Damage associated with vascular compromise during dislocation.
  • Injury to the popliteal artery Popliteal Artery The continuation of the femoral artery coursing through the popliteal fossa; it divides into the anterior and posterior tibial arteries. Popliteal Fossa: Anatomy or vein: the vessels of the popliteal fossa Popliteal fossa The popliteal fossa or the “knee pit” is a diamond-shaped, fat-filled, shallow depression on the posterior aspect of the knee joint. The popliteal fossa is located at the dorsal aspect of the knee and contains an increased number of lymph nodes as well as structures of the neurovascular system that travel from the thigh to the lower leg. Popliteal Fossa: Anatomy may be injured with KD KD An acute, febrile, mucocutaneous condition accompanied by swelling of cervical lymph nodes in infants and young children. The principal symptoms are fever, congestion of the ocular conjunctivae, reddening of the lips and oral cavity, protuberance of tongue papillae, and edema or erythema of the extremities. Kawasaki Disease. Delay in diagnosis or recognition, treatment with reduction, and/or surgical repair may lead to arterial injury Arterial Injury Hemothorax and amputation Amputation An amputation is the separation of a portion of the limb or the entire limb from the body, along with the bone. Amputations are generally indicated for conditions that compromise the viability of the limb or promote the spread of a local process that could manifest systemically. Amputation. 
  • Compartment syndrome Compartment Syndrome Compartment syndrome is a surgical emergency usually occurring secondary to trauma. The condition is marked by increased pressure within a compartment that compromises the circulation and function of the tissues within that space. Compartment Syndrome: a surgical emergency Surgical Emergency Acute Abdomen usually occurring secondary to trauma. Compartment syndrome Compartment Syndrome Compartment syndrome is a surgical emergency usually occurring secondary to trauma. The condition is marked by increased pressure within a compartment that compromises the circulation and function of the tissues within that space. Compartment Syndrome is marked by increased pressure within a fascial compartment, which compromises the circulation Circulation The movement of the blood as it is pumped through the cardiovascular system. ABCDE Assessment and function of the tissues within that space.

References

  1. Mohseni, M, & Simon, LV. (2021). Knee dislocation. StatPearls. Treasure Island (FL): StatPearls Publishing. http://www.ncbi.nlm.nih.gov/books/NBK470595/
  2. Raj, MA, Mabrouk, A, & Varacallo, M. (2021). Posterior cruciate ligament knee injuries. StatPearls. Treasure Island (FL): StatPearls Publishing. http://www.ncbi.nlm.nih.gov/books/NBK430726/
  3. Henrichs A. (2004). A review of knee dislocations. Journal of Athletic Training, 39(4), 365–369.
  4. Duprey, K, & Lin, M. (2010). Posterior knee dislocation. The Western Journal of Emergency Medicine, 11(1), 103–104.

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