Arthrokinematic and Magnetic Resonance Imaging-Based Outcomes of Customized Lateral Wedge Insoles in Medial Compartment Knee Osteoarthritis: Six-Month Interim Findings of a Prospective Cohort Study.

Abstract

Introduction: Knee osteoarthritis (OA) is a leading musculoskeletal disorder with a prevalence of 22-39% in India, representing approximately one-third of 500 million individuals affected globally. The epidemiological burden increased 2.66-fold from 23.46 million (1990) to 62.35 million (2019). Mechanical axis deviation drives OA progression; finite element analysis (FEA) provides a non-invasive tool to evaluate tissue-level biomechanical changes. Prospective Indian OA cohort studies combining arthrokinematic and magnetic resonance imaging (MRI)-based outcomes are lacking.

Materials and methods: A non-randomized prospective cohort study - carrying inherent risk of selection bias, confounding by indication, and baseline imbalance - was conducted at AIIMS Rajkot in collaboration with the Saurashtra University after acquiring ethical approval (IEC: AIIMS/RAJKOT/6th IEC/FB/02) and CTRI registration (CTRI/2025/02/081105). Fifty-five knees in 45 patients (male knees n = 19, female knees n = 36; mean age 58.3 ± 10.3 years; body mass index [BMI] 28.2 ± 5.3 kg/m2) with knee OA and mechanical axis deviation were enrolled; and allocation to the customized lateral wedge insole group (n = 28) or to conventional conservative management (n = 27) was made by the treating orthopaedic surgeon on the basis of mechanical axis deviation severity, without randomization or allocation concealment. Osteokinematic parameters were assessed by calibrated goniometry at 3-month intervals; MRI osteoligamentous metrics (joint space width [JSW], meniscal thickness) were obtained at baseline, 6 and 18months. This article presents the observations collected at the end of the 1st project year, namely the 6-month MRI follow-up and four 3-monthly biomechanical assessment outcomes. 22 out of 55 participants (40.0%) attended the 6-month MRI assessment and two 3-monthly biomechanical analyses, thereby constituting the complete-case analysis set (11 study group, 11 control group). No imputation was performed, and outcome assessment was not blinded. No validated patient-reported outcome measure was collected. Paired/unpaired t-tests and two-way repeated-measures analysis of variance with Bonferroni correction (Statistical Package for the Social Sciences v16.0; α = 0.05); analyses were unadjusted for confounders.

Results: Of the 55 enrolled knees, 22 (40.0%) were successfully followed up at the 6-month assessment, representing substantial attrition of 60.0% (n = 33), and all outcomes below refer to this analysis set (n = 22). Knee flexion increased (+4.4°; P = 0.02) and external rotation showed the greatest gain (+5.64°; P < 0.01); medial JSW widened (+0.40 mm; P < 0.01) and medial meniscus thickness increased (+0.16 mm; P = 0.05). Internal rotation (+1.56°; P = 0.06) and extension (+1.56°; P = 0.08) did not reach significance levels. In exploratory, non-prespecified sex-stratified analyses (male knees n = 10, female knees n = 12), males showed larger gains in internal rotation (+4.6°; P < 0.001) and external rotation (+8.3°; P < 0.001), and greater medial JSW widening (+0.46 mm; P < 0.01) than females (+0.36 mm; P = 0.01), with a sex × time interaction of P = 0.03. Females maintained higher absolute knee flexion throughout than their male counterparts. These are within-cohort changes over time: The n = 22 analysis set comprises 11 study-group and 11 control-group participants, and no between-group comparison of the insole against conventional care was performed. Twelve-month and 18-month outcomes and the FEA are not yet available and are not reported here in this article.

Conclusion: At 6 months, use of a customized lateral wedge insole was associated with widening of the medial tibiofemoral joint space (+0.40 mm; P < 0.01) and with improved knee kinematics in this Indian cohort. These are associations rather than demonstrated treatment effects, because allocation was not randomized, 60.0% of enrolled participants were lost to follow-up, outcome assessment was unblinded, and no validated patient-reported outcome measure was collected. Their clinical importance also remains undetermined, since changes of this magnitude approach the precision limits of the measurement methods used. The apparent sex differences rest on small, unpowered subgroups and should be regarded as hypothesis-generating. Subject-specific FEA and 12-18-month follow-up are ongoing, but an adequately powered randomized trial with validated patient-reported endpoints will be needed before any disease-modifying effect can be claimed.