Introduction: Posterior thigh muscle injuries in athletes are common, and prediction of recovery time would be of value.
Hypothesis: Knee active range of motion deficit 48 hours after a unilateral posterior thigh muscle injury correlates with time to full recovery.
Study design: Cohort study (prognosis); Level of evidence, 2.
Methods: One hundred sixty-five track and field athletes with acute, first-time, unilateral posterior thigh muscle injuries were prospectively evaluated regarding knee active range of motion deficit. This was compared with the uninjured side 48 hours after injury. A control group was also examined. Ultrasound was used to image the muscle lesion. All athletes were managed nonoperatively with the same rehabilitation protocol. The "full rehabilitation time" (interval from the injury to full athletic activities) was recorded.
Results: Range of motion of the affected leg was decreased in the 165 injured athletes compared with the uninjured side and the control group. Sonography identified abnormalities in 55% (90 of 165) of the injured athletes. The biceps femoris was the most commonly affected muscle (68 of 90 [75%]). The musculotendinous junction (proximal or distal) was involved in 93% (85 of 90) of lesions. Eighty-one percent (133 of 165) of athletes had active range of motion deficit of less than 20 degrees, and had returned to full performance at 2 weeks. In 6 of 165 athletes (3.6%), with active range of motion deficit of more than 30 degrees, recovery time exceeded 6 weeks, with a significant correlation between full rehabilitation time and active range of motion deficit (chi(2) = 152.560; P = .0001).
Conclusion: Knee active range of motion deficit is an objective and accurate measurement, predicting recovery time in elite athletes.