Anatomy, Bony Pelvis and Lower Limb, Posterior Thigh Muscles

BICEPS FEMORIS LONG HEAD

• Origin: Common (conjoint) tendon from the superior medial quadrant of the posterior ischial tuberosity (with semitendinosus)
• Insertion: Majority onto the fibular head; also the lateral collateral ligament of the knee and lateral tibial condyle
• Action: Flexion of the knee, and lateral rotation of the tibia; extension of the hip joint
• Innervation: Tibial nerve (a portion of the sciatic nerve)
• Arterial Supply: Perforating (muscular) branches of profunda femoris artery, inferior gluteal artery, and the superior muscular branches of the popliteal artery

BICEPS FEMORIS SHORT HEAD

• Origin: Lateral lip of linea aspera, the lateral intermuscular septum of the thigh, and lateral supracondylar ridge of femur
• Insertion: Majority on the fibular head; and lateral collateral ligament of the knee, and lateral tibial condyle
• Action: Flexion of the knee, and lateral rotation of the tibia
• Innervation: Common peroneal nerve (a portion of the sciatic nerve)
• Arterial Supply: Perforating (muscular) branches of profunda femoris artery, inferior gluteal artery, and the superior muscular branches of the popliteal artery

SEMIMEMBRANOSUS

• Origin: Superior lateral aspect of the ischial tuberosity
• Insertion: The posterior surface of the medial tibial condyle
• Action: Extension of the hip, flexion of the knee, and medial rotation of the tibia (specifically with knee flexion)
• Innervation: Tibial nerve (a portion of the sciatic nerve)
• Arterial Supply: Perforating (muscular) branches of profunda femoris artery, inferior gluteal artery, and the superior muscular branches of the popliteal artery

SEMITENDINOSUS

• Origin: The common (conjoint) tendon from the superior medial quadrant of the posterior ischial tuberosity (with biceps femoris long head)
• Insertion: Superior aspect of the medial tibial shaft (into the distal portion of the pes anserinus along with the gracilus and sartorius muscles)
• Action: Extension of the hip and flexion of the knee, medial rotation of the tibia (specifically with knee flexion)
• Innervation: Tibial nerve (a portion of the sciatic nerve)
• Arterial Supply: Perforating (muscular) branches of profunda femoris artery, inferior gluteal artery, and the superior muscular branches of the popliteal artery

Variations in hamstring muscles and their attachments are rare. One variation that noted in current research is the distinct origination of the biceps femoris long head and semitendinosus from separate tendons attached to the ischial tuberosity opposed to their more common, shared, origination from the common (conjoint) tendon to the ischial tuberosity.[1]

Additional isolated variations have appeared through cadaver dissections. Of note, a lack of union between the short and long head of biceps femoris, while still inserting into the fibular head on one cadaver. On another, two anomalous muscles, one arising as a “third head of biceps femoris” and another as an independent muscle inserting into semitendinosus, were seen on post-mortem dissection.[2]

Surgical treatments involving the hamstring muscles are rare as conservative treatment for injuries is the preferred first-line management. Patients may present with ecchymosis over the posterior thigh and a stiff-legged gait to avoid flexion at the hip and knee. Patients with avulsion injuries of the proximal hamstring muscles from their origin may benefit from surgical treatment of their injuries regarding pain levels and functional outcomes, particularly if they are young and active. Surgical procedures have been shown to have better results when used in the treatment of more severe avulsion injuries as well as being performed on more acute injuries in comparison to chronic avulsion injuries.[3] The decision to indicate a patient for surgery depends on the distance that the tendon has retracted as well as the chronicity of symptoms. 

Other surgical considerations regarding the hamstring muscles include autografting hamstring tendons for the reconstruction of the ACL in patients with tears. Removal of the semitendinosus and sometimes gracilus tendons from their insertions site into the pes anserinus for use in ACL repairs has been shown to have advantages over other autograft methods (such as using the patellar tendon) with less post-operative knee pain and an overall easier recovery following surgery.[4]

Hamstring muscle injuries are currently one of the most common injuries suffered by athletes. Patients largely report strains due to quick changes in speed and excessive lengthening of the hamstrings due to a particular inciting event or experiencing proximal tendinopathy resulting from excessive use over long periods. Two types of acute hamstring strains appear in the current literature. Type 1, involving mainly the proximal tendon muscle junction of the biceps femoris, results during the terminal deceleration of the swing phase of running as the patient prepares to plant their foot resulting in eccentric contraction of the muscle.[5] Type 2 hamstring strains result from the extensive lengthening of the muscle resulting in overstretching and injury to the proximal tendon area of the semimembranosus muscle. These types of injuries most commonly occur during actions involving flexion of the hip with an extension of the knee.[6] Of these two types of injuries, type 2 has been shown to require more time to fully heal and return to sports in comparison to type 1.[7]

Clinically, patients typically describe hamstring muscle strains as beginning acutely during physical activities involving the lower body with a sharp or stabbing pain in the proximal posterior thigh with increasing pain with active extension of the hip or flexion of the knee. A possible pop and/or delayed appearance of ecchymosis around the area of pain presents in more extreme cases.[8] On physical exam, patients generally exhibit pain in the posterior thigh with passive stretching of the hamstring muscles and with activation or use of the hamstring muscles. Plain radiographs of the pelvis may show a small avulsion fracture from the ischial tuberosity; however, an MRI is necessary if the radiographs are negative, and a high index of suspicion exists.[9] Treatment for hamstring injuries largely resolves around decreasing inflammation and damage near the time of injury with resting of the muscles, NSAIDs, and icing. Following initial treatment of the injury, varying progressions of physical therapy are used to progress patients back to full use of their hamstrings while avoiding re-injury, a very common occurrence with hamstring injuries.[10][11] Researchers have explored additional treatment modalities in pursuit of faster recovery, including the use of intramuscular corticosteroid injections and administration of platelet-rich plasma (PRP) all with varying results and efficacy at this time.[12][13]