The adaptive change of patellofemoral joint after arthroscopic discoid lateral meniscus plasty: An observational study

The purpose of this study was to investigate the patellofemoral joint adaptive changes after discoid lateral meniscus (DLM) plasty. Forty-one patients with unilateral complete type DLM tears were included in this study. Demographic variables, including gender, age, body mass index (BMI), injury to operation interval, type of injury, and follow-up time, were recorded. The evolution of physical examination, imaging index, and functional score were analyzed by Chi-squared test, Wilcoxon signed ranks test, and Friedman test. Mann–Whitney test was used to analyze the difference at different time points between group PFI > 1.6 and PFI < 1.6. After the patients received arthroscopic DLM plasty, the positive rate of Patella grinding test increased from 19.5% to 29.3%, and it showed significant increased at last follow-up time point (48.8%) (P = .005). Mechanical axis deviation (MAD) significant decreased from −0.7 ± 2.1 mm to −9.4 ± 3.2 mm (P < .001). Lateral patellofemoral angle (LPFA) and lateral shift distance (LSD), respectively, decreased from 11.9 ± 5.8° and 1.0 ± 4.0 mm to 7.2 ± 4.5° and −0.5 ± 3.3 mm (P < .001). Patellofemoral index (PFI) increased from 1.7 ± 0.3 to 1.9 ± 0.4 (P < .001). Kujala score and Lysholm score, respectively, increased from 65.9 ± 10.0 and 85.2 ± 6.4 mm to 61.8 ± 10.2 and 89.5 ± 5.0 (P < .001). Only LSD in group > 1.6 were significant lower than those in group < 1.6 (>1.6: −1.5 ± 2.8, −1.6 ± 2.7, −1.5 ± 2.6; <1.6: 0.8 ± 3.4, 0.4 ± 3.6, 0.6 ± 2.8. P = .010,.038,.011) at the 3 postoperative follow-up time points. After arthroscopic plasty for complete type DLM which decreased the thickness and width of the residual meniscus, in turn causing the varus deformity significantly decreased or a valgus inclination developed. Moreover, the consequent changes of patellofemoral joint caused a certain amount of patellar tilt and patellar dislocation, might aggravated the symptomatic anterolateral knee pain or the lateral patellar compression syndrome.