Modified knee extension training for treatment of patellar malalignment

Abstract

Background: Patients with patellar malalignment (PM) are common in orthopedic clinics. Conservative treatment first for PM is generally supported. Generally, reinforcing vastus medialis obliquus (VMO) strength is most convincing. Knee extension had been reported to be able to initiate VMO activities in electromyogram (EMG). Also, goosestep training had been reported to be able to upraise VMO/vatus lateralis (VL) ratio in EMG. Purpose: The purpose of this prospective study was to investigate clinical effects of modified knee extension training on treating lateral patellar tilt or subluxation. Methods: Thirty-seven consecutive adult patients (average: 52 years) were treated with modified knee extension training. It was performed once each day and each time needed 50 times (about one minute). Plain knee radiographs of anteroposterior, lateral, and Merchant's axial views were taken before treatment. Exclusion criteria were trochlear dysplasia (＞ 144° of sulcus angle), patellar alta or dislocation, symmetrical mediolateral patellofemoral (P-F) joint space (P-F index = 1), and snapping hips clinically. Ten weeks later, clinical outcome using modified Kujala score (5 items with 40 points) and Merchant's axial radiograph (congruence angle, lateral P-F angle, and P-F index) were compared statistically. Results: All 37 patients with 68 knees (32 bilaterally and 4 unilaterally) were followed at the outpatients' department (OPD) at 10-12 weeks. Before treatment, none of patients were satisfactory (average knee score: 27.2 points). At the latest follow-up, 89% of patients (33/37) were satisfactory (p ＜ 0.001) with an average knee score of 33.1 (p = 0.01). Only the P-F index was statistically significant before and after treatment (3.6 vs. 2.1, p ＜ 0.001) on Merchant's axial radiographs. Conclusion: The described technique may be one of excellent techniques for conservative treatment of PM. The technique is simple and an 89% success rate is relatively acceptable. The P-F index may be practical for follow-up of treatment effect.