Posterior Flashcards
Posterior compartment of the thigh
The muscles in this compartment are the hamstrings: semimembranosus and semitendinosus medially, and biceps femoris laterally.
With the exception of the short head of biceps femoris, they all extend the hip and flex the knee, arise from the ischial tuberosity, and are supplied by the tibial nerve.
The short head of biceps femoris arises from the linea aspera of the femur, does not extend the hip and is supplied by the common fibular nerve
Semitendinosus
This muscle arises from the inferomedial aspect of the ischial tuberosity. The muscle decreases in size from above downwards so that midway down the thigh, it is replaced by a cord-like tendon that lies in a gutter on semimembranosus. Its tendon passes behind the medial femoral condyle, and curves forwards to insert into the medial aspect of the upper tibial shaft, posterior to sartorius and inferior to gracilis
Semimembranosus
This muscle arises from the posterolateral aspect of the ischial tuberosity, with its upper part being a long, flat tendon (“membrane”) which lies deep to semitendinosus and the long head of biceps femoris.
It inserts distally into a groove on the posterior aspect of the medial tibial condyle, with expansions that diverge obliquely across the capsule of the knee joint and inferiorly over the popliteus to the soleal line of the tibia
Biceps femoris
The long head arises from the medial aspect of the ischial tuberosity with semitendinosus. It passes across the semimembranosus tendon to join the short head (from the linea aspera) in the distal part of the thigh. The heads form a common tendon which inserts into the lateral aspect of the head of the fibula. Its tendon is easily palpable on the lateral aspect of the knee
Popliteal fossa
The popliteal fossa is a diamond-shaped space behind the knee, bounded proximally by the diverging hamstrings (semimembranosus and semitendinosus medially, and biceps femoris laterally) and distally by the converging heads of gastrocnemius. The roof is formed by the fascia lata, which is pierced by the small saphenous vein and the posterior femoral cutaneous nerve. Its floor is formed by the popliteal surface of the distal femur, the capsule of the knee joint, and the fascia overlying the popliteus
Medial –> lateral:
Artery, vein, nerve (common fibular and tibial)
Superficial posterior compartment of the leg
This group comprises gastrocnemius, plantaris and soleus, which join to form the strong calcaneal tendon (tendo Achilles) which inserts into the posterior aspect of the calcaneus. As the gastrocnemius and plantaris originate proximal to the knee, they flex the knee and plantarflex the ankle. They are all supplied by branches of the tibial nerve
Gastrocnemius
This muscle arises by two heads from the distal end of the posterior aspect of the femur. The medial head arises just proximal to the medial condyle, while the lateral head arises from the lateral aspect of the lateral condyle itself. They converge to lie side by side, with a dense aponeurosis beneath them. The fleshy part of the muscle extends to about midcalf, where it forms the calcaneal tendon. A bursa separates the tendon from the bone. This muscle is a strong plantar flexor at the ankle, and a weaker flexor at the knee
Plantaris
Short muscle belly with a very long tendon.
It arises from the distal end of the lateral supracondylar ridge of the femur. Its tendon passes downwards and medially between soleus and gastrocnemius, blending with the medial part of the calcaneal tendon
Soleus
This muscle originates from the upper quarter of the posterior aspect of the fibula, the soleal line of the tibia, and the middle third of the medial border of the tibia.
Its fibres form a fibrous arch over the popliteal vessels. The muscle is flat and has a characteristic appearance, with a dense aponeurosis on both surfaces. It inserts into the deeper aspect of the calcaneal tendon, and flexes the foot at the ankle.
It is a very powerful multipennate muscle. In addition to its function in locomotion, it is also an important venous pump. Perforating veins from the great saphenous vein enter the soleus muscle, and when the muscle contracts, the veins are emptied, thus aiding venous return to the heart
Deep group of posterior compartment of the leg
This group consists of popliteus and three muscles that are inserted into the foot: flexor hallucis longus, flexor digitorum longus, and tibialis posterior. Tibialis posterior is the deepest of the three and lies almost entirely on the interosseous membrane. The three tendons pass under the flexor retinaculum into the sole of the foot and insert into the foot. All four muscles are supplied by the tibial nerve
Popliteus
This muscle has two proximal attachments. The lateral part attaches as a round tendon from the anterior end of the popliteal groove on the lateral femoral condyle, while the medial part attaches as a flat aponeurosis to the lateral meniscus and capsule of the knee joint. Its distal attachment is to the popliteal surface of the posterior tibia above the soleal line. It is supplied by the tibial nerve, a branch of which curves around the distal border of the muscle to enter its deep surface. Its action is to stabilise and control the position of the lateral meniscus, and to rotate the femur laterally on the tibia to “unlock” the knee
Flexor hallicus longus
This is a large and powerful muscle that originates from the distal three-quarters of the fibula and the interosseous membrane. Its tendon lies very deep at the ankle, grooving the talus and the inferior surface of the sustentaculum tali of the calcaneus. It runs forwards in the sole to insert into the plantar surface of the base of the distal phalanx of the hallux (great toe). It is supplied by the tibial nerve, and its action is to flex the hallux and maintain the medial longitudinal arch of the foot in walking and running
Flexor digitorum longus
This muscle arises from the medial part of the posterior surface of the tibia below the soleal line. After entering the sole, it crosses the flexor hallucis longus tendon and divides into four tendons, each inserting into the plantar surface of the respective bases of the four lateral toes and passing through a decussation in the tendons of flexor digitorum brevis in a manner identical to that seen in the hand between flexor digitorum superficialis and profundus. It is supplied by the tibial nerve. Its action is to flex the toes in walking and running.
Tibialis posterior
This muscle arises from the lateral half of the posterior surface of the tibia below the soleal line, the interosseous membrane, and the upper part of the medial surface of the fibula. It inserts primarily into the tuberosity of the navicular, with slips going to the cuboid, cuneiforms and bases of the medial four metatarsals. It flexes and inverts the foot and supports the longitudinal arches. It is supplied by the tibial nerve.
As the tendons of the above three muscles all pass behind the medial malleolus, their secondary action is to plantarflex the foot at the ankle.
