The hamstring muscles connect at the pelvis and top of the lower leg bones and are responsible for bending the knee and straightening the hip during activities such as running, jumping and kicking. These muscles are comprised of three tendons that can be damaged with overtraining.
Hamstring tendonitis is a condition in which tissue damage and inflammation occurs in one or more of the hamstring tendons. Lower hamstring tendonitis affects the area where the tendons attach at the top of the lower leg, causing pain in the back of the knee. The condition is common among youth and adult basketball players and runners who may have tight muscles. It also is particularly common in sports requiring frequent acceleration and deceleration such as football, basketball and soccer. 
Occasionally, lower hamstring tendonitis develops suddenly because too much stress or tension takes place, beyond what the tendons can withstand. Most commonly, this occurs during rapid acceleration while running or performing a long kick. Inadequate warm-up, or fatigue because of multiple endurance activities without adequate rest, can contribute to the potential for sudden onset of hamstring tendonitis.
Symptoms typically include pain that develops gradually in the inner or outer areas of the back of the knee. Pain also may radiate into the top of the calf or back of the thigh. A less severe case may only generate a knee ache or stiffness that increases with rest following activities requiring strong or repetitive contraction of the hamstring muscle.
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