Hamstring is a muscle group which forms the back of the thigh extending over two joints, namely the hip joint and the knee joint. It consists of three muscles and these are the Semitendinosus, Semimembranosus and the Biceps femoris. The three muscles converge on the bones of the lower leg and merges with the connective tissues of the strong hamstring tendon, which attaches itself to the tibia and the fibula separately.
The hamstring tendon is the main structure, which attaches the hamstring muscle group to the lower leg bones. As such, it should be able to tolerate an enormous amount of stress exerted during various hip and knee joint movements as the muscle group extends over both these joints. Therefore, the hamstring tendon is made up of thick connective tissues, which provides the necessary tensile strength to withstand even the harshest of moves. However, as with most tendons subjected to enormous amount of stressors, the hamstring tendon can also give away at one point if the tolerance level of the tendon is exceeded during certain types of sudden and forceful movements.
When considering the specific movements supported by the hamstring tendon and the hamstring muscle group as a whole, bending of the knee joint and extending the leg at the hip joint are the two main movements. Therefore, the hamstring tendon can be seen in action at times of walking, running, jumping or any movement that involves movements at the hip and at the knee joint. Thus, the tendon can be injured or the hamstring muscles could be torn in sports such as sprinting, soccer, basketball…etc.
In addition to the bending or flexing of the knee joint and extending the lower limb at the hip joint when the upper body is fixed, the hamstring tendon is also useful in rotating the knee joint medially when the knee is bent. The semitendinosus and semimembranosus muscles of the hamstring mainly support this movement. However, the short and long heads of the biceps femoris does the opposite as it rotates the knee joint laterally when the knee joint is bent in relation to certain movements.
As mentioned earlier, the role played by the hamstring muscle is important in most daily activities involving the lower limbs. In most of these movements, the hamstring tendon and the muscle group acts as an antagonist to the knee extension movements of the quadriceps muscles during walking.
However, although these movements are the ultimate effect of contractions in the hamstring muscle group, by providing the support structure for its attachment to the bones, the hamstring tendon allows the muscle group to perform such functions effectively with a firm grip on the lower leg bones.