Anatomy: Leg and Foot

Popliteal Fossa

A diamond-shaped space located posterior to the knee joint bounded superomedially by semimembranosus and semitendinosus, superolaterally by biceps femoris, and inferomedially and inferolaterally by the medial and lateral heads of gastrocnemius; contents include the popliteal artery, popliteal vein, tibial nerve, common fibular nerve, small saphenous vein, plantaris muscle, popliteal lymph nodes, and fat.

Anterior Cruciate Ligament (ACL)

An intra-articular knee ligament attaching from the anterior tibia to the posterior femur that limits anterior displacement of the tibia relative to the femur and prevents knee hyperextension.

Posterior Cruciate Ligament (PCL)

An intra-articular knee ligament attaching from the posterior tibia to the anterior femur that limits posterior displacement of the tibia relative to the femur and prevents knee hyperflexion.

Tibial Collateral Ligament (MCL)

A broad medial collateral ligament of the knee joint connecting the medial epicondyle of the femur to the medial condyle and shaft of the tibia.

Fibular Collateral Ligament (LCL)

A cord-like lateral collateral ligament of the knee joint connecting the lateral epicondyle of the femur to the head of the fibula.

Talocrural Joint (Ankle Joint)

A synovial hinge joint formed by the distal tibia, medial malleolus, lateral malleolus, and the trochlea of the talus that permits dorsiflexion and plantarflexion of the foot.

Subtalar Joint

An articulation located between the talus and calcaneus that allows inversion and eversion of the foot.

Transverse Tarsal Joint

A compound joint comprised of the talonavicular and calcaneocuboid articulations that permits inversion and eversion of the foot.

Deltoid Ligament

A thick, strong medial ankle ligament complex formed by four bands (anterior tibiotalar, tibionavicular, posterior tibiotalar, and tibiocalcaneal ligaments) that functions to resist excessive eversion of the foot.

Lateral Ankle Ligaments

A group of three ligaments (anterior talofibular, posterior talofibular, and calcaneofibular) that are weaker than the medial ligaments and act to resist foot inversion.

Anterior Talofibular Ligament (ATFL)

A lateral ankle ligament extending from the lateral malleolus to the talus that is most commonly injured during inversion ankle sprains.

Plantar Calcaneonavicular Ligament (Spring Ligament)

A key plantar foot ligament connecting the calcaneus to the navicular bone that supports the head of the talus and maintains the medial longitudinal arch of the foot.

Anterior Compartment of the Leg

The muscular leg compartment containing the ankle dorsiflexors and toe extensors (tibialis anterior, extensor hallucis longus, extensor digitorum longus, fibularis tertius), innervated by the deep fibular nerve (L4–S2) and supplied by the anterior tibial artery.

Lateral Compartment of the Leg

The muscular leg compartment containing foot evertors (fibularis longus and fibularis brevis), innervated by the superficial fibular nerve (L4–S2).

Superficial Posterior Compartment of the Leg

The leg compartment containing the gastrocnemius, soleus, and plantaris muscles, which function to plantarflex the foot and/or flex the leg; all innervated by the tibial nerve (L4–S3).

Deep Posterior Compartment of the Leg

The leg compartment containing the popliteus, tibialis posterior, flexor digitorum longus, and flexor hallucis longus muscles, innervated by the tibial nerve (L4–S3) and supplied by the posterior tibial and fibular arteries.

Tarsal Tunnel

A space situated deep to the flexor retinaculum inferior and posterior to the medial malleolus transmitting (from anterior to posterior) the Tibialis posterior tendon, Digitorum (flexor digitorum longus) tendon, posterior tibial Artery, tibial Nerve, and Hallucis (flexor hallucis longus) tendon ("Tom, Dick, And Nervous Harry").

Tibialis Anterior

An anterior leg muscle originating from the lateral tibia and inserting onto the medial cuneiform and 1st metatarsal; innervated by the deep fibular nerve (L4–S2) to dorsiflex and invert the foot.

Fibularis Longus

A lateral leg muscle originating from the proximal two-thirds of the fibula and crossing the plantar foot to insert on the medial cuneiform and 1st metatarsal; innervated by the superficial fibular nerve (L4–S2) to everts and assist in plantarflexion.

Gastrocnemius

A superficial posterior leg muscle originating from the medial and lateral femoral condyles and inserting onto the calcaneus via the calcaneal tendon; innervated by the tibial nerve (L4–S3) to plantarflex the foot and flex the leg.

Tibialis Posterior

A deep posterior leg muscle originating from the interosseous membrane, tibia, and fibula, and inserting onto the navicular, cuneiforms, cuboid, and bases of metatarsals 2–4; innervated by the tibial nerve (L4–S3) to plantarflex and invert the foot.

Popliteus

A deep posterior leg muscle originating on the lateral femoral condyle and lateral meniscus and inserting on the posterior tibia; innervated by the tibial nerve (L4–S3) to flex the leg weakly and unlock the knee by laterally rotating the femur on a fixed tibia during weight-bearing.

Foot Drop

A clinical motor deficit resulting from damage to the common fibular nerve, leading to loss of innervation to ankle dorsiflexors and evertors and causing the toes to drag on the ground during the swing phase of gait.

Dorsalis Pedis Artery

The anterior vascular supply of the foot arising as the distal continuation of the anterior tibial artery across the anterior ankle; its pulse is palpated lateral to the tibialis anterior tendon.

Great Saphenous Vein

A major superficial vein originating from the medial aspect of the dorsal venous arch, coursing anterior to the medial malleolus, and ascending the leg to drain into the femoral vein.

Small Saphenous Vein

A superficial vein originating from the lateral aspect of the dorsal venous arch, passing posterior to the lateral malleolus, and ascending to drain into the popliteal vein within the popliteal fossa.

Common Fibular Nerve

A major nerve branch of the sciatic nerve (L4–S2) that winds around the neck of the fibula before dividing into the superficial and deep fibular nerves.

Tibial Nerve

A nerve branch of the sciatic nerve (L4–S3) providing motor supply to all muscles of the posterior leg and sole of the foot, dividing near the tarsal tunnel into the medial and lateral plantar nerves.

Deep Fibular Nerve

A nerve branch (L4–S2) originating from the common fibular nerve that innervates all muscles of the anterior leg and dorsal foot, while conveying sensory supply to the skin of adjacent sides of the 1st and 2nd toes.

Superficial Fibular Nerve

A nerve branch (L4–S2) originating from the common fibular nerve that innervates the lateral leg compartment muscles and supplies skin over the distal lateral leg and dorsum of the foot.

Saphenous Nerve

A cutaneous nerve branch of the femoral nerve that accompanies the great saphenous vein to provide sensory innervation to the skin over the anteromedial leg and medial foot.

Sural Nerve

A sensory nerve formed by the junction of the medial and lateral sural cutaneous nerves that supplies the posterolateral distal leg and lateral aspect of the foot.

Plantar Aponeurosis

A dense, strong band of deep fascia on the plantar aspect of the foot extending from the calcaneus to the toes, providing passive support to maintain the longitudinal arches.

Pes Planus (Flat Feet)

A clinical condition characterized by the breakdown or flattening of the medial longitudinal arch of the foot due to loss of dynamic muscle or passive ligamentous support.

Plantar Interossei

Three intrinsic muscles located in layer 4 of the plantar foot innervated by the lateral plantar nerve that adduct digits 3–5 toward digit 2 ("PADs").

Dorsal Interossei

Four intrinsic muscles located in layer 4 of the plantar foot innervated by the lateral plantar nerve that abduct digits 2–4 away from digit 2 ("DABs")