The hamstring muscles are comprised of 3 parts, originating from the sit bone and inserting onto the back of the knee.
Often pain is felt at the base of the buttock or the center of the back of the thigh, and sitting is particularly painful. Hamstring pulls can be very painful and can result in limping and even bruising that extends all the way down the leg.
These injuries can with any physical exertion, whether over stretching in yoga or running to catch a taxi! Sometimes diagnostic ultrasound or MRI tests are ordered to assess the extent of the hamstring injury.