Combined Hip and Knee Strengthening Compared With Knee Strengthening for Individuals With Lateral Patellar Dislocation: A Single-blind, Superiority, Randomized Controlled Trial

Abstract

ObjectiveTo investigate whether a combined hip and knee muscle strengthening program is superior to a knee strengthening program for people after lateral patellar dislocation (LPD). DesignSingle-blind, superiority, randomized controlled trial with 48 weeks follow-up. SettingPhysiotherapy out-patient clinic. ParticipantsForty individuals aged 16 or older, with a history of non-traumatic LPD were randomized to a knee-based strengthening (KBSG) or quadriceps and hip strengthening exercise (HQSG) program (N=40). Inclusion criteria included a positive apprehension sign, pain on palpation along the medial retinaculum, and J sign. Exclusion criteria included restricted range of motion (<90° knee flexion), and traumatic or postsurgical LPD. InterventionsConcealed randomization was performed using random permuted blocks of size 4. Individuals received their corresponding exercise program according to randomization and group allocation: knee-based strengthening (n=20) or combined hip and quadriceps strengthening (n=20) twice weekly for 8 weeks over 16 appointments. Main Outcome MeasuresPrimary outcome was the Lysholm Knee Score. Secondary outcomes included Numerical Pain Ratings Scale (NPRS) at rest and during effort, Norwich Patellar Instability Score (NPIS), Kujala Anterior Knee Pain Scale (AKPS), Lower Extremity Functional Scale (LEFS), 4 domains of the WHOQOL-Bref, and recurrence rate. Patient-reported outcome measures were assessed from the baseline to 48 weeks. Assessments were performed by a physiotherapist who was blinded to the group allocation. Data were analyzed by using a repeated-measures ANOVA model with Tukey's post hoc test after an intention-to-treat principle. ResultsAt the primary time-point of 8 weeks, there were no substantial between-group differences in the Lysholm Knee Score: mean difference=-6.8 (95% CI -14.3 to 3.7); NPIS: mean difference=23.5 (95% CI 5.6 to 41.3); AKPS: mean difference=-1.54 (95% CI -8.6 to 5.6), NPRS at rest and during effort (mean difference=0.32 (95% CI -0.37 to 1); and mean difference=0.68 (95% CI -0.9 to 1.86); LEFS mean difference=-1.08 (95% CI -5.9 to 2.4), WHOQOL-Bref domains (physical health: mean difference=-0.12, (95% CI -1.26 to 1.02); psychological: mean difference=-0.32 (95% CI -2.04 to 1.4); social relations: mean difference=-0.7 (95% CI -2.2 to 0.82); environment: mean difference=0.44 (95% CI -1 to 1.9), and recurrence rate (P=.69). ConclusionThis study indicates that combined hip and knee muscle strengthening is not superior to knee-based strengthening for LPD treatment. The limitations stemming from the underpowered nature of the trial must be acknowledged, concerning the potential oversight of moderate intervention effects.