Study: Return-to-Play Predictions for Hamstring Injuries Hamstrung by Variability

Think you can predict how long it will take an athlete with a hamstring injury to return to play based on the athlete's history and an initial clinical examination? Some researchers say you probably can't—and magnetic resonance imaging (MRI) probably won't help.

In a study published in the British Journal of Sports Medicine (pdf) researchers followed the progress of 180 male athletes with acute hamstring injury in an effort to analyze the predictive value of patient history and initial clinical examination, as well as any additional insight added by MRI. All of the athletes participated in a supervised physical therapy program, and were cleared for return to sport by either a physician or a physical therapist (PT).

Using a more in-depth statistical analysis than in previous studies, the investigators calculated that patient history and clinical examination explained only 29% of the total variance in time to return to sport among the participants. Adding MRI increased that variance by just 2.8%—for a total of 31.8%.

Based on their findings, the authors write, “Clinicians cannot provide an accurate time to return to sport” based on patient history, initial examination, or MRI. However, they add, “this is not a call to abandon MRI in clinical practice,” a resource that could be valuable for confirming the diagnosis and informing patients about their injuries.

The initial examination included pain experienced during range-of-motion testing, manual muscle testing, the active slump test, and measuring length and width of the injury through tenderness to palpation. The variables that were correlated with length of time before return to sport included pain score at the time of injury, being forced to stop within 5 minutes of the onset of pain, painful resisted knee flexion, and length of injury.

One of the limitations of the study is that the criteria for determining return to sport were determined by the individual physicians and PTs. But, the investigators note, while scientifically not optimal, this may better reflect the reality of patient care.