Imaging and Clinical Factors Associated With Return to Play and Recurrence After Quadriceps Muscle Strain Injury.

BACKGROUND: Limited information is available about factors that impact prognosis after quadriceps muscle strain injury, particularly injuries involving the rectus femoris. This study aims to determine whether baseline clinical and radiological findings are associated with time to return to play (RTP) and injury recurrence after rectus femoris muscle strain injury in elite Australian Football players. HYPOTHESIS: Baseline magnetic resonance imaging (MRI) findings related to the specific anatomical location and severity of rectus femoris injury will influence time to RTP and recurrence. STUDY DESIGN: Cross sectional study. LEVEL OF EVIDENCE: Level 4. METHODS: A total of 163 quadriceps muscle strain injuries from 127 elite Australian Football players were analyzed. The impact of clinical (player characteristics, injury mechanism, injury type) and MRI findings (anatomical location of injury, injury severity) on RTP and injury recurrence were explored using time to event (survival) analyses. RESULTS: RTP time frames (means and standard deviations) were longest for injuries affecting the rectus femoris proximal free tendon (50.4 ± 16.2 days) and central aponeurosis (33.7 ± 20.4 days). Central aponeurosis injuries with disruption took longer to RTP compared with central aponeurosis injuries without disruption (hazard ratio [HR] = 0.47; P = 0.03), and longer than injuries involving the anterior (HR = 0.59; P = 0.05) or posterior aponeuroses (HR = 0.56; P = 0.02). Increased severity of aponeurotic disruption was also associated with prolonged RTP (P < 0.01). Reinjuries were associated with longer RTP than index injuries (adjusted HR = 0.49; P = 0.04). No clinical or MRI factors were associated with injury recurrence. CONCLUSION: Rectus femoris injuries with significant connective tissue disruption, particularly those affecting the proximal free tendon or central aponeurosis, as well as reinjuries, may require extended time for rehabilitation and RTP. CLINICAL RELEVANCE: An understanding of baseline MRI findings related to the specific anatomical location and severity of connective tissue disruption can enhance the ability of clinicians to estimate expected RTP time frames after rectus femoris injury.