How do the hamstrings work?
The hamstrings are comprised of three separate muscles (semitendinosus, semimembranosus, and biceps femoris) that run along the back of the hip and knee joints. Collectively they function to extend the hip and flex the knee during activities such as running and sprinting. They originate on a part of the pelvis called the ischial tuberosity, a prominence that can be felt as the bony part of the buttock when you sit down on a hard surface.
How are hamstring injuries diagnosed?
Hamstring injuries or tears are diagnosed by combining clinical symptoms (pain, weakness, deformity) with MRI findings indicative of tendon degeneration, partial thickness tearing, or complete tearing.
How are hamstring injuries treated?
The most common hamstring injury is a muscle strain due to excessive exertion or forceful contraction without proper conditioning (sprinting, hurdling, water skiing). In severe cases, partial or complete muscle tears can occur resulting in severe weakness and bruising. In general, hamstring strains take 4 – 6 weeks for full recovery while partial or complete muscle tears may take 3 – 6 months. The majority of strains can be treated without surgery using rest, ice, physical therapy, and platelet-rich-plasma (PRP) injections when indicated. Proper stretching and conditioning is the best method of preventing future injuries.
Hamstring tendon injuries are different from muscle injuries, and are divided into two types: acute and chronic.
- Acute Hamstring Tendon Injury
Acute tendon tears occur due to forceful contraction while bracing to prevent a fall or injury. Most tendon tears are partial thickness, incompletely involving the width of the tendon, and do have the potential to heal without surgery. Occasionally the healing process needs to be supplemented with a series of PRP injections. Complete tears involving all three tendons tend to retract (pull away from the bone) and have a lower likelihood of successful healing, typically necessitating surgical hamstring tendon repair.
- Chronic Hamstring Tendinosis
Tendinosis refers to an age related degeneration of tendon quality that renders the tissue more susceptible to injury with every day activities. Unlike the case for acute tears, chronic tendinosis can develop without a discrete injury and typically affects patients > 50 years of age. Progressive delamination of the fibers within the tendon can lead to partial thickness tearing. The body’s natural healing response is often inadequate and results in chronic inflammation and painful scarring. In the absence of a frank tear, PRP injections are effective at stimulating a healing response and can significantly reduce pain and improve function. If injections fail to provide adequate improvement or there is a frank tear, surgical hamstring tendon repair is the most reliable means of achieving successful healing and return to function.