The hamstrings are a group of three muscles, biceps femoris, semitendinosus, and semimembranosus, running along the posterior thigh, all originating at the ischial tuberosity and crossing both the hip and knee joints. This dual-joint span means the hamstrings work to extend the hip and flex the knee simultaneously, and their length is directly compromised by sitting, which shortens them at both ends. They are among the most frequently strained muscles in sport, and proximal hamstring tendinopathy has become a significant challenge in distance runners and sedentary workers alike.
| Origin | Ischial tuberosity of the pelvis; Lateral lip of the linea aspera of the femur |
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| Insertion | Head of the fibula and lateral condyle of the tibia; Medial surface of the tibia via the pes anserinus; Posterior medial condyle of the tibia |
| Nerve Supply | Sciatic nerve, tibial division (L5, S1, S2) for biceps femoris long head, semitendinosus, semimembranosus; Common fibular division (L5, S1, S2) for biceps femoris short head |
| Blood Supply | Inferior gluteal artery; Perforating branches of the deep femoral artery |
| Actions | Flexion of the knee; Extension of the hip (long head of biceps, semitendinosus, semimembranosus); Internal rotation of the tibia (semitendinosus and semimembranosus when knee is flexed); External rotation of the tibia (biceps femoris when knee is flexed) |
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During running, the hamstrings are most active in the late swing phase, decelerating the extending knee before foot strike, and in early stance, helping extend the hip. This late-swing eccentric loading phase is the primary mechanism of hamstring muscle tears in sprinters.
Hamstring strains are the most common muscle injury in football, rugby, and athletics, with the biceps femoris long head at the musculotendinous junction being the most frequently affected site. Proximal hamstring tendinopathy, degeneration at the ischial tuberosity attachment, is a particularly stubborn condition in distance runners and cyclists, presenting as deep buttock pain that worsens on sitting, and requires a graduated loading programme rather than rest. The Nordic curl and sprint-specific eccentric exercises have strong evidence for reducing hamstring re-injury rates.
The ischial tuberosity origin is palpable deep in the gluteal fold with the hip flexed. The three bellies are palpable along the posterior thigh, the biceps femoris on the lateral side, the semitendinosus as a visible cord on the medial side, and the semimembranosus deeper and medial to it. Both distal tendons are easily felt at the back of the knee.
A tear within the muscle belly or at the musculotendinous junction, most commonly the biceps femoris long head, occurring during explosive sprinting or kicking, producing sudden posterior thigh pain, tenderness, and sometimes bruising that tracks distally.
Degenerative change in the common hamstring origin at the ischial tuberosity, producing deep buttock pain that is provoked by sitting on firm surfaces, hills, and progressive running loads, and requires a structured heavy slow resistance programme for resolution.
A high-energy injury, typically from forceful hip flexion with the knee extended, that tears all three hamstring tendons from the ischial tuberosity, producing sudden severe buttock pain, bruising, and significant weakness in hip extension and knee flexion requiring surgical reattachment.
