Acute quadriceps muscle strains - Magnetic resonance imaging features and prognosis

Background: There has been no research examining the magnetic resonance imaging findings, and in turn the prognosis, for a series of acute quadriceps muscle strains. Hypothesis: The magnetic resonance imaging findings of acute quadriceps muscle strain injuries are helpful in predicting their prognosis. Study Design: Causal-comparative study. Method: Forty professional players of Australian Rules football were followed over 3 years. Magnetic resonance imaging examinations were performed within 24 to 72 hours of muscle-strain injury. Imaging features of muscle strain injury included the anatomical location, size (cross-sectional area and length), and site (proximal, middle, or distal). The time from injury to return to full training was termed the rehabilitation interval. Results: 25 clinical quadriceps muscle strain injuries occurred, with 15 cases involving the rectus femoris. The rectus femoris injuries could be further categorized into cases with straining about the central tendon (n = 7, mean rehabilitation interval = 26.9 days) or cases with straining in the periphery (n = 8, mean rehabilitation interval = 9.2 days). Six cases involved one of the vastus muscles (mean rehabilitation interval = 4.4 days). Three players had normal magnetic resonance imaging examinations (mean rehabilitation interval = 5.7 days). Conclusions: The rectus femoris-central tendon injury is the red flag diagnosis associated with a significantly longer rehabilitation interval. Clinical Relevance: Magnetic resonance imaging is helpful in predicting the prognosis for acute quadriceps strains.