The Hamstring Muscle Group
The hamstring muscles consist of three primary muscles: the biceps femoris (long and short head), semitendinosus, and semimembranosus 1, 2.
Anatomical Composition
The hamstring muscle complex is located in the posterior compartment of the thigh and comprises:
Biceps femoris - Has two heads:
- Long head (biarticular - crosses both hip and knee)
- Short head (monoarticular - crosses only the knee)
Semitendinosus (biarticular)
Semimembranosus (biarticular)
All three muscles except the short head of biceps femoris originate from the ischial tuberosity and span across both the hip and knee joints 2, 3.
Functional Characteristics
These muscles work together to:
- Extend the hip joint
- Flex the knee joint
The biarticular nature of most hamstring components (crossing both hip and knee) makes them particularly vulnerable to injury during activities involving eccentric contractions, especially during terminal swing phase of sprinting when the muscles experience peak strain and force 4.
Clinical Relevance
The hamstring group is frequently referenced in perioperative positioning guidelines because stretching these muscles beyond comfortable preoperative range can place tension on the sciatic nerve, which travels through this muscle group 5. The biceps femoris is specifically mentioned in positioning protocols as an example of the hamstring muscle group 6.
Understanding hamstring anatomy is essential for injury prevention, surgical planning (particularly in ACL reconstruction where hamstring autografts are commonly used), and rehabilitation protocols 7, 8.