Understanding Hamstring Injuries
The hamstrings are a group of three muscles located in the back of the thigh. They are the most common muscles injured in professional football and usually occur during the “push-off” phase of running.
Several factors can predispose players to injury, including older age, previous hamstring injury, less flexibility in the hamstrings, lack of hamstring strength, and fatigue. Many players will get hamstring pulls in the beginning of training camp as they make the transition from off-season workouts to live, on-the-field action.
The three hamstring muscles are the semimembranosis, semitendinosis, and the biceps femoris. The biceps femoris is further divided into a long head and a short head, and is the most commonly injured muscle of the three.
All of the hamstrings originate on the pelvis and insert onto the back of the tibia (lower leg bone). They therefore cross both the hip joint and the knee joint, serving as extensors of the hip and flexors of the knee.
Injuries to these muscles are very common, particularly in sprinting athletes, such as soccer, baseball, and football players. The diagnosis is usually made based on a physical exam. Patients will report pain in the back of the thigh, particularly as they kick the leg backwards during running. They may also report sudden pain or the sensation that someone has stabbed them in the back of the leg and they are unable to run.
When examining these muscles one can often see swelling and bruising, signs that the muscle has been injured. In severe cases there may be a palpable defect in the muscle. The severity of the injury is graded on a scale from 1-3. Grade 1 injuries are mild, with only a few muscle fibers being torn and no loss in muscle strength. Grade 2 injuries are moderate injuries with a loss in hamstring strength. Grade 3 injuries are the most severe, representing a complete tear of the hamstrings and a loss in strength.
Sometimes an MRI is obtained to further evaluate the extent of the injury as well as to localize it.
The majority of acute hamstring injuries are partial thickness tears. In other words, only part of the muscle has been torn. These can most often be treated successfully with rest, ice, compression, elevation (also known as RICE), and nonsteroidal anti-inflammatory drugs (NSAIDs), such as ibuprofen. This will be done for the first week, followed by progressive functional physical therapy for three to four more weeks, as needed.
Return to full activity is usually allowed when the patient is pain free, has full range of motion, and full strength. More severe injuries, such as partial tears with significant loss of strength and complete tears, lead to longer periods of convalescence (rest) with conservative management.
In one study, the time before return to vigorous activity ranged from three months to one and a half years. Such a long period of lost playing time is less than ideal for professional and elite athletes, and some have advocated more aggressive treatment in this group. In a study published out of Columbia-Presbyterian Medical Center on professional football players with severe hamstring tears with palpable defects, an intramuscular corticosteroid injection lead to a return to full activity time of 7.6 days, and 85% of the players did not miss a single game. Final examination revealed no strength deficits, normal muscle bulk and tone, and the ability to generate normal power.(1)
Complete hamstring tears with retraction of the muscle can lead to significant functional impairment and lost playing time. In a study out of Duke University Medical Center, Forty-two percent of patients with these complete tears were unable to run or participate in sports requiring agility.(2)
Injury which leads to retraction of the hamstring muscles can lead to decreased function and strength. Rarely, some complete tears have been shown to scar in and entrap the sciatic nerve, leading to radiculopathy of the nerve, which then requires surgical release.
Therefore, surgery is indicated to repair completely torn and retracted hamstring tendons, especially for patients who need to be able to run or be sufficiently agile to participate in sport.
Surgical repair for partial hamstring tears that have failed rehabilitation has been reported. In one series, approximately 85% of athletes with surgical repair of a partial tear returned to their previous level of play.
For complete ruptures, there are several reported series in the literature. With the current techniques used, approximately 75-85% of athletes with a surgical repair return to their previous level of play or activity.
Surgical repair of chronic complete tears – caused either by a delay in surgical intervention or a trial of rehabilitation - is more technically challenging, may increase the likelihood of sciatic nerve involvement, increases the need for postoperative bracing, and reduces postoperative outcome in terms of hamstring strength and endurance.
In addition, only approximately 58% of athletes with complete tears of their proximal hamstrings are able to return to sport without repair, and their return to play is most often to a lower level than it was prior to injury.
Therefore, earlier surgical intervention may be indicated in cases of a complete tear with retraction of the hamstrings and significant loss of function. Return to full activity usually occurs at between six and nine months post-op.