The hamstring muscles are the muscles located on the back of the thigh. They are comprised of three muscles (biceps femoris, semitendinosus, semimembranosus) which function to bend the knee. The biceps femoris and semitendinosus hamstring tendons fuse together into what is called the common tendon which attaches to the ischial tuberosity on the pelvic bone (commonly called the sit bone). The semimembranosis attaches just laterally (on the side) to the common tendon insertion. The gluteal muscles overly the proximal hamstring attachment. The sciatic nerve and inferior gluteal nerves are in very close proximity to the proximal hamstring tendons.
Proximal hamstring injuries can be acute (sudden onset) or chronic (occuring over time).
Acute Injuries in Adults:
Commonly called a high hamstring tear, the proximal hamstring tear/ rupture usually has an abrupt onset. It can result from a fall, forced splits or a mechanism where the knee is straight (extended) and the hip is in extreme flexion (hyper flexion) when the hamstring tendon pulls off the origin attachment. Waterskiing is a common activity where these tears occur. Patients often report a pop and the inability to walk. The rupture can also produce extensive bruising along the back of the thigh and down into the leg. Cramping is often felt with complete ruptures. Transient (occasional) numbness and tingling can occur as well. The ruptures can be partial or complete. Complete ruptures typically indicate the common tendon and semi-membranosis have been torn from the ishcial tuberosity. Partial tears occur when a percentage of the tendon is left intact. High grade tears are usually greater than 50%. Low grade tears are usually below 50%
Acute Injuries in Youth:
In younger populations where the pelvic bone growth plates have not closed the tendon pulls off a bony fragment from its attachment. This classifies the injury as an avulsion fracture of the ischial tuberosity.
Chronic proximal hamstring injuries can stem from a partial tear that does not heal properly or from repeated micro trauma. Often seen in runners, patient usually report continued pain and soreness with activities.
How are proximal hamstring injuries diagnosed?
Evaluation for a proximal hamstring is done by your health care provider. A physical exam is often accompanied by x-rays and an MRI. The x-rays are done to see if there has been any bone pulled off and to check for additional fractures. An MRI will show the tendon and determine the severity of the injury. In the case of complete tendon rupture, the MRI will show the tear and determine whether the tendon has retracted (pulled away) from its normal position.
What is the treatment for proximal hamstring injury?
Physical therapy is often employed as a treatment for chronic and partial hamstring tears. Exercises often focus on swelling control, gait training and core exercises.
In the case of an ischial tuberosity avulsion in a youth athlete, there is often a period of protected weight bearing followed by physical therapy.
Acute tears sometimes warrant surgical repair. The best time to make the repair is within the first two weeks after the injury. Acute tears that go longer without repair can have significant retraction and form scar tissue. This scar tissue can often entrap part of the sciatic nerve causing pain, numbness and tingling.