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Popliteal Fossa: Anatomy

The popliteal fossa or the “knee pit” is a diamond-shaped, fat-filled, shallow depression on the posterior aspect 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. The popliteal fossa is located at the dorsal aspect of the knee and contains an increased number of lymph Lymph The interstitial fluid that is in the lymphatic system. Secondary Lymphatic Organs nodes as well as structures of the neurovascular system that travel from the thigh Thigh The thigh is the region of the lower limb found between the hip and the knee joint. There is a single bone in the thigh called the femur, which is surrounded by large muscles grouped into 3 fascial compartments. Thigh: Anatomy to 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. The boundaries are formed by various muscles of the thigh Thigh The thigh is the region of the lower limb found between the hip and the knee joint. There is a single bone in the thigh called the femur, which is surrounded by large muscles grouped into 3 fascial compartments. Thigh: Anatomy and 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.

Last updated: Aug 15, 2022

Editorial responsibility: Stanley Oiseth, Lindsay Jones, Evelin Maza

Boundaries of the Popliteal Fossa

Popliteal fossa

  • Also known as the “knee pit” or “hough” 
  • Diamond-shaped depression on the posterior aspect 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
  • 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 analog of the cubital fossa Cubital Fossa The cubital fossa is the region anterior to the elbow joint. The cubital fossa is seen as the triangular depression between the brachioradialis and pronator teres muscles. The 4 important structures of the cubital fossa (from lateral to medial) are the radial nerve, tendon of the biceps brachii muscle, brachial artery, and median nerve. Cubital Fossa: Anatomy

Boundaries

Multiple muscles of the dorsal thigh Thigh The thigh is the region of the lower limb found between the hip and the knee joint. There is a single bone in the thigh called the femur, which is surrounded by large muscles grouped into 3 fascial compartments. Thigh: Anatomy and 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 form the majority of the boundaries of the popliteal fossa.

Boundaries Structures
Superolaterally
Superomedially
Inferolaterally
Inferomedially
Roof
  • 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
  • Popliteal fascia Fascia Layers of connective tissue of variable thickness. The superficial fascia is found immediately below the skin; the deep fascia invests muscles, nerves, and other organs. Cellulitis (continuous with the fascia Fascia Layers of connective tissue of variable thickness. The superficial fascia is found immediately below the skin; the deep fascia invests muscles, nerves, and other organs. Cellulitis lata superiorly and the fascia Fascia Layers of connective tissue of variable thickness. The superficial fascia is found immediately below the skin; the deep fascia invests muscles, nerves, and other organs. Cellulitis cruris inferiorly)
Floor
  • Capsule Capsule An envelope of loose gel surrounding a bacterial cell which is associated with the virulence of pathogenic bacteria. Some capsules have a well-defined border, whereas others form a slime layer that trails off into the medium. Most capsules consist of relatively simple polysaccharides but there are some bacteria whose capsules are made of polypeptides. Bacteroides 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
  • Distal femur
  • 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
  • Popliteus muscle
The boundaries of the popliteal fossa

The boundaries of the popliteal fossa

Image by BioDigital, edited by Lecturio.

Muscles of the Popliteal Region

MuscleOriginInsertionInnervationFunction
Semimembranosus Semimembranosus Thigh: Anatomy 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 Tibial nerve
Semitendinosus Semitendinosus Thigh: Anatomy Superomedial surface 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
Biceps femoris Biceps femoris Thigh: Anatomy Head of the 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 and the lateral tibial condyle
Gastrocnemius Gastrocnemius Leg: Anatomy
  • Lateral head: lateral femoral condyle
  • Medial head: medial femoral condyle
Helps form the calcaneal or Achilles tendon, inserted into the posterior aspect of the calcaneus Calcaneus The largest of the tarsal bones which is situated at the lower and back part of the foot, forming the heel. Foot: Anatomy 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
Popliteus
  • Lateral femoral condyle
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, below the medial tibial condyle
  • Internal 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 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

Contents of the Popliteal Fossa

The popliteal fossa is the location of many important nerves and vessels of the lower extremity and is the main channel for the neurovascular system between the thigh Thigh The thigh is the region of the lower limb found between the hip and the knee joint. There is a single bone in the thigh called the femur, which is surrounded by large muscles grouped into 3 fascial compartments. Thigh: Anatomy and 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.

Contents of the popliteal fossa

Contents of the popliteal fossa

Image by BioDigital, edited by Lecturio.

Mnemonic

To recall the contents of the popliteal fossa from medial to lateral, remember to Serve and Volley Next Ball

Vessels

Popliteal artery: 

  • Continuation of the femoral artery Femoral Artery The main artery of the thigh, a continuation of the external iliac artery. Femoral Region and Hernias: Anatomy, beginning at the level of the adductor hiatus in the adductor magnus Adductor magnus Thigh: Anatomy muscle of the thigh Thigh The thigh is the region of the lower limb found between the hip and the knee joint. There is a single bone in the thigh called the femur, which is surrounded by large muscles grouped into 3 fascial compartments. Thigh: Anatomy
  • Popliteal artery gives off 5 branches that anastomose 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:
    • Superior medial and lateral genicular arteries Arteries Arteries are tubular collections of cells that transport oxygenated blood and nutrients from the heart to the tissues of the body. The blood passes through the arteries in order of decreasing luminal diameter, starting in the largest artery (the aorta) and ending in the small arterioles. Arteries are classified into 3 types: large elastic arteries, medium muscular arteries, and small arteries and arterioles. Arteries: Histology
    • Middle genicular artery
    • Inferior medial and lateral genicular arteries Arteries Arteries are tubular collections of cells that transport oxygenated blood and nutrients from the heart to the tissues of the body. The blood passes through the arteries in order of decreasing luminal diameter, starting in the largest artery (the aorta) and ending in the small arterioles. Arteries are classified into 3 types: large elastic arteries, medium muscular arteries, and small arteries and arterioles. Arteries: Histology
  • The deepest vessel within the popliteal fossa
  • Enters the posterior compartment of 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 and bifurcates into the anterior and posterior tibial arteries Arteries Arteries are tubular collections of cells that transport oxygenated blood and nutrients from the heart to the tissues of the body. The blood passes through the arteries in order of decreasing luminal diameter, starting in the largest artery (the aorta) and ending in the small arterioles. Arteries are classified into 3 types: large elastic arteries, medium muscular arteries, and small arteries and arterioles. Arteries: Histology

Popliteal vein:

  • Continuation of the posterior tibial vein
  • Becomes the femoral vein proximally to the popliteal fossa
  • Found between the popliteal artery (deeply) and tibial nerve (superficially)
  • The tributaries of the popliteal vein are the deep veins Veins Veins are tubular collections of cells, which transport deoxygenated blood and waste from the capillary beds back to the heart. Veins are classified into 3 types: small veins/venules, medium veins, and large veins. Each type contains 3 primary layers: tunica intima, tunica media, and tunica adventitia. Veins: Histology of 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: the posterior and anterior tibial veins Veins Veins are tubular collections of cells, which transport deoxygenated blood and waste from the capillary beds back to the heart. Veins are classified into 3 types: small veins/venules, medium veins, and large veins. Each type contains 3 primary layers: tunica intima, tunica media, and tunica adventitia. Veins: Histology, the common fibular veins Veins Veins are tubular collections of cells, which transport deoxygenated blood and waste from the capillary beds back to the heart. Veins are classified into 3 types: small veins/venules, medium veins, and large veins. Each type contains 3 primary layers: tunica intima, tunica media, and tunica adventitia. Veins: Histology, and the small saphenous vein.
  • The small saphenous vein enters the fossa through the popliteal fascia Fascia Layers of connective tissue of variable thickness. The superficial fascia is found immediately below the skin; the deep fascia invests muscles, nerves, and other organs. Cellulitis and drains into the popliteal vein between the 2 heads of the gastrocnemius Gastrocnemius Leg: Anatomy muscle.

Nerves

The main nerves of the popliteal fossa are the 2 branches of the sciatic nerve Sciatic Nerve A nerve which originates in the lumbar and sacral spinal cord (l4 to s3) and supplies motor and sensory innervation to the lower extremity. The sciatic nerve, which is the main continuation of the sacral plexus, is the largest nerve in the body. It has two major branches, the tibial nerve and the peroneal nerve. Gluteal Region: Anatomy, which is the largest branch of the lumbosacral plexus and bifurcates at the superior angle of the popliteal fossa into the following: 

  1. Tibial nerve: 
    • More medial and larger of the 2 branches
    • Runs deeply through the fossa and into the posterior compartment of 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
    • Gives off motor Motor Neurons which send impulses peripherally to activate muscles or secretory cells. Nervous System: Histology branches to the muscles of the popliteal region
    • Gives off a cutaneous branch that joins a branch from the common fibular nerve to form the sural nerve
  2. Common fibular (peroneal) nerve: 
    • More lateral and smaller of the 2 branches
    • Runs along the medial border of the biceps femoris Biceps femoris Thigh: Anatomy muscle before exiting the fossa superficially
Innervation of the popliteal fossa

Innervation of the popliteal fossa

Image by BioDigital, edited by Lecturio.

Lymph Lymph The interstitial fluid that is in the lymphatic system. Secondary Lymphatic Organs nodes

  • There are 6–8 lymph Lymph The interstitial fluid that is in the lymphatic system. Secondary Lymphatic Organs nodes embedded in the fat of the popliteal fossa.
  • They are divided into superficial and deep popliteal lymph Lymph The interstitial fluid that is in the lymphatic system. Secondary Lymphatic Organs nodes:
    • Superficial group: receive lymph Lymph The interstitial fluid that is in the lymphatic system. Secondary Lymphatic Organs from the accompanying nodes of the small saphenous vein
    • Deep group: receive lymph Lymph The interstitial fluid that is in the lymphatic system. Secondary Lymphatic Organs from the superficial nodes, 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, and 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

Clinical Relevance

The following is an important clinical concept related to the structures found within the popliteal fossa:

  • Popliteal pulse: The 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 of the popliteal artery pulse is usually performed with the knee in slight flexion Flexion Examination of the Upper Limbs, which relaxes the popliteal fascia Fascia Layers of connective tissue of variable thickness. The superficial fascia is found immediately below the skin; the deep fascia invests muscles, nerves, and other organs. Cellulitis and the muscles of the posterior thigh Thigh The thigh is the region of the lower limb found between the hip and the knee joint. There is a single bone in the thigh called the femur, which is surrounded by large muscles grouped into 3 fascial compartments. Thigh: Anatomy ( semimembranosus Semimembranosus Thigh: Anatomy, semitendinosus Semitendinosus Thigh: Anatomy, and biceps femoris Biceps femoris Thigh: Anatomy). The pulse is best felt in the inferior part of the fossa but may be difficult to palpate due to the deep location of the popliteal artery. 

The following conditions are of clinical significance regarding the popliteal fossa:

  • Popliteal cyst Popliteal cyst A synovial cyst most commonly at the back of the knee. Osteoarthritis (Baker’s cyst): a synovial cyst that is the most common mass Mass Three-dimensional lesion that occupies a space within the breast Imaging of the Breast that occurs in the popliteal space. A popliteal cyst Popliteal cyst A synovial cyst most commonly at the back of the knee. Osteoarthritis is a fluid-filled sac usually associated with 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 arthritis Arthritis Acute or chronic inflammation of joints. Osteoarthritis that develops in the semimembranosus Semimembranosus Thigh: Anatomy bursa. A popliteal cyst Popliteal cyst A synovial cyst most commonly at the back of the knee. Osteoarthritis may resolve without treatment but occasionally will require aspiration or may rupture leading to swelling Swelling Inflammation that resembles deep vein thrombosis Thrombosis Formation and development of a thrombus or blood clot in the blood vessel. Epidemic Typhus.
  • Popliteal artery aneurysm Aneurysm An aneurysm is a bulging, weakened area of a blood vessel that causes an abnormal widening of its diameter > 1.5 times the size of the native vessel. Aneurysms occur more often in arteries than in veins and are at risk of dissection and rupture, which can be life-threatening. Thoracic Aortic Aneurysms: an abnormal dilatation of the popliteal artery more than 50% of the artery’s diameter that can lead to compression Compression Blunt Chest Trauma of the tibial nerve with diminished plantar flexion Flexion Examination of the Upper Limbs and paresthesia 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 posterolateral aspect of 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. Diagnosis is based 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 of a pulsatile mass Mass Three-dimensional lesion that occupies a space within the breast Imaging of the Breast or auscultation of a bruit.
  • Knee dislocation Knee dislocation A dislocation of the knee (tibiofemoral joint) 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. Knee Dislocation: generally secondary to high-impact trauma, such as a fall from height or a motor Motor Neurons which send impulses peripherally to activate muscles or secretory cells. Nervous System: Histology vehicle collision. Dislocations are most commonly anterior or posterior, depending on the mechanism of injury. Treatment is an immediate reduction and evaluation of the vascular system, specifically the popliteal artery. Vascular evaluation includes serial exams and may include surgical exploration. Interruption of the blood supply can lead to acute 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, gangrene Gangrene Death and putrefaction of tissue usually due to a loss of blood supply. Small Bowel Obstruction, and even 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 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/or 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
  • Tibial nerve damage: Posterior dislocation 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 or lacerations of the popliteal region may damage the tibial nerve. Injury results in weakness in plantar flexion Flexion Examination of the Upper Limbs of the calf and the intrinsic muscles 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.

References

  1. Drake, R.L., Vogl, A.W., Mitchell, A.W.M. (2014). Gray’s Anatomy for Students (3rd ed.). Philadelphia, PA: Churchill Livingstone.
  2. Chummy, S.S. (2011) Last’s Anatomy (12th ed.). Edinburgh: Churchill Livingstone.

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