Popliteal Fossa: Anatomy

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.

Muscles of the Popliteal Region

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.

Mnemonic

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

• Semimembranosus/Semitendinosus
• Artery
• V ein EIN Atypical hyperplasia Endometrial Hyperplasia and Endometrial Cancer
• Nerve
• Biceps femoris

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

Lymph nodes Lymph Nodes They are oval or bean shaped bodies (1 – 30 mm in diameter) located along the lymphatic system. Lymphatic Drainage System: Anatomy

• There are 6–8 lymph nodes Lymph Nodes They are oval or bean shaped bodies (1 – 30 mm in diameter) located along the lymphatic system. Lymphatic Drainage System: Anatomy embedded in the fat of the popliteal fossa.
• They are divided into superficial and deep popliteal lymph nodes Lymph Nodes They are oval or bean shaped bodies (1 – 30 mm in diameter) located along the lymphatic system. Lymphatic Drainage System: Anatomy:
  • 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.