Hamstrings

Hamstrings refer to one of the tendons that make up the borders of the space behind the knee. You can feel some string-like tendons that are at the back of the knee in form of a long muscle.

Anatomy of the Vastus Hamstrings

The hamstrings are composed of four muscles. These are the

• semitendinosus,
• semimembranosus,
• biceps femoris - long head, and
• biceps femoris - short head

The three muscles of the posterior thigh (semitendinosus, semimembranosus, and biceps femoris-long head) bend the knee, while three of the four straighten the hip.

The short head of the biceps femoris, with its divergent origin and innervations, is not involved in hip extension, and thus is sometimes excluded from the 'hamstring' characterization.

Functions of the Hamstrings

The hamstrings play a crucial role in many daily activities, such as, walking, running, jumping, and controlling some movement in the trunk. In fact, injuring or straining your hamstrings has led to the end of the careers of many sportsmen.

The hamstrings cross and act upon two joints - the hip and the knee.

Semitendinosus and semimembranosus extend the hip when the trunk is fixed or extend the trunk when the hip is fixed; they also flex the knee and inwardly rotate the lower leg when the knee is bent.

The long head of the biceps femoris extends the hip as when beginning to walk; both short and long heads flex the knee and outwardly rotate the lower leg when the knee is bent.

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