Tendinitis of the hamstring tendon would present as pain over the sit bone. The pain is usually worse after long periods of sitting or driving, or using the muscle with the hip bent, like doing deep lunges, a lot of stretches, or increasing your running speed or hill training. The pain may be felt at the start of exercise and then disappear as the body warms, only to return after you have cooled down.
Iliotibial band Syndrome (ITB Syndrome)
The Hamstrings have some anchors on the outside to the Iliotibial band. In this case your pain will be more towards the outside of the thigh and usually travels all the way to the outside of the knee with a very tender spot on the outside of the knee. ITB Syndrome can be confused with a hamstring injury.
Peripheral nerve entrapment of the Sciatic nerve
The sciatic nerve is the supply chain of nerves for the leg. The nerve can become pinched along it’s way down the back of your leg usually by scar tissue from previous injury. Even if you only had a fairly minor hamstring injury. Your pain may be limited to the back of the thigh or spread below the knee, depending on the branches of the nerve that are entrapped. The pain will have a tingling quality, you may experience pins and needles, numbness or weakness.
Femur stress fracture
Repetitive strain and excessive training may cause a stress fracture of the thigh bone (femur). This would be suspected if the pain is more a dull and constant, irrespective of rest or walking around. Stress fracture may not be visible on normal X-rays, so referral to an Orthopaedic surgeon may be necessary to request either an MRI or CT-scan. This type of pain usually gets worse when you lay on your side, and may wake you up at night.