Hamstring Tears
The hamstring muscles run down the back of the thigh beginning at the bottom of the pelvis, crossing the knee joint and ending on the tibia below the knee. Hamstring muscles help to extend the leg straight back and bend the knee. A pulled hamstring or strain is an injury to one or more of the muscles at the back of the thigh. Symptoms include sharp pain in the back of the thigh, swelling, bruising, and weakness.
Achilles Tendonitis 
