A retrospective review of delayed knee mobilization following extensor mechanism repair

Objectives: Traumatic extensor mechanism (EM) rupture of the knee is a debilitating injury with considerable post-operative morbidity. While surgical repair is standard, rehabilitation protocols vary. This study aimed to evaluate clinical outcomes of patients managed with delayed knee flexion, initiated at least 6 weeks after EM repair. Methods: We retrospectively reviewed patients who underwent acute surgical repair of the EM at a level 1 trauma center over a 10-year period. Adults with patellar fractures, quadriceps, or patellar tendon ruptures were included. All were allowed weight-bearing as tolerated but restricted from active or passive knee flexion for 6 weeks. Outcomes included the final range of motion, return to pre-injury activity, and post-operative complications. Results: Of 149 patients included, the mean body mass index (BMI) was 31.5. Patellar fractures comprised 67% of cases, followed by quadriceps tendon ruptures (31.8%) and patellar tendon ruptures (6.8%). Most had no wound complications (94.7%) or revision surgeries (93.96%). Patients with tendon ruptures were older (59.0 vs. 54.5 years, P = 0.04) and had a higher BMI (36.0 vs. 27.9, P < 0.0001) than those with fractures. Median final flexion was 120° for fractures and 110° for tendon ruptures ( P = 0.93). Manipulation under anesthesia was rare (4.1% vs. 3.9%), and fixation loss occurred in 5.3% of patients. Conclusion: Delayed flexion beginning at 6 weeks after EM repair is associated with a favorable range of motion and low complication rates. These findings suggest that delayed mobilization does not compromise outcomes and is a safe alternative to early motion protocols.