Peak knee adduction moment and impulse are not related to changes in self-reported pain or physical function over 12 months in individuals with medial knee osteoarthritis

Abstract

Purpose: Dynamic joint loading is thought to be a major contributing factor to the development and progression of knee joint structural changes. The external knee adduction moment (KAM) during walking is a valid and reliable proxy for the load on the medial tibiofemoral compartment of the knee and is related to radiographic knee OA severity and risk of structural disease progression. However, no study has longitudinally examined the relationship between baseline KAM and changes in pain or physical function in a cohort with knee OA. The purpose of this study was to examine the relationship between peak KAM and KAM impulse with changes in self-reported pain and self-reported physical function over a 12-month period. Methods: Data from 141 individuals with medial knee OA (80 females, 61 males, age: 64.5±8.0yrs, BMI: 28.6±4.5m/kg2) who participated in a clinical trial were analyzed. The clinical trial showed no significant effect of lateral wedge insoles on pain or function compared to control insoles, thus data from treatment groups were pooled for this analysis. All participants underwent baseline three-dimensional gait analysis, and completed baseline and follow-up self-report measures of pain and function. Peak KAM and the KAM impulse were determined via gait analysis (8-camera VICON, 3 AMTI force plates). Pain and physical function at baseline and at 12 months were evaluated using a) The Western Ontario and McMaster Universities Arthritis Index (WOMAC) and b) numeric rating scales (NRS) to rate average overall weekly pain, average weekly pain when walking and average restriction to daily activities. Paired t-tests were used to examine changes in pain and function over 12-months in the whole cohort. Initially, unadjusted linear regression models were performed to examine the relationships between peak KAM (independent variable and change in self-reported pain and function (dependent variables). Models were repeated adjusting for a) age, sex, and body mass index and b) with the additional covariate of treatment group. All analyses were repeated using KAM impulse as the independent variable. Results: Baseline and follow-up self-reported pain and function scores are reported in Table 1. The cohort showed a small but significant improvement in WOMAC pain and function scores (Table 1). Neither peak KAM nor KAM impulse were associated with changes in self-reported WOMAC pain or function (Table 2). Similar to WOMAC scores, the NRS scores also significantly improved over time (Table 1). However, these improvements were less than the minimal clinically important differences. Neither peak KAM nor KAM impulse were associated with changes in self-report NRS pain or activity restrictions (Table 2). Conclusions: We found no relationship between parameters of the KAM and change in self-reported pain and function over 12-months in our cohort. Future research targeting those who exhibit worsening of pain and function over time, longer follow-up duration and incorporating performance-based measures of physical function is warranted.Table 1Baseline and follow-up self-reported pain and function scoresBaselineFollow-upMean Difference (95%CI)p-valueWOMAC Pain (0-20)7.2 (2.9)6.3 (3.3)0.9 (0.4, 1.4)0.001WOMAC Function (0-68)23.7 (11.1)20.2 (12.2)3.5 (1.8, 5.1)<0.001Average weekly pain when walking (0-10)4.3 (2.1)3.1 (2.4)1.2(0.8, 1.5)<0.001Average weekly pain (0-10)4.2 (1.9)3.1(2.2)1.1(0.7, 1.4)<0.001Average weekly restriction to activities (0-10)3.8 (2.3)3.1 (2.5)0.7 (0.4, 1.1)<0.001Lower scores indicate less pain/better function Open table in a new tab Table 2Relationship between KAM and changes in self-reported pain and functionUnivariate analysisMultivariate analysis*Multivariate analysis**Regression coefficient (95% CI)p-valueRegression coefficient (95% CI)p-valueRegression coefficient (95% CI)p-valueWOMAC PainPeak Knee Adduction Moment (Nm/BW*ht%)Knee Adduction Moment Impulse (Nm.s/BW*ht)-0.11 (-0.62, 0.41)-0.51 (-1.85, 0.83)0.680.45-0.08 (-0.62, 0.47)-0.55 (-1.93, 0.82)0.780.43-0.06 (-0.61, 0.48)-0.53 (-1.92, 0.85)0.810.45WOMAC FunctionPeak Knee Adduction Moment (Nm/BW*ht%)Knee Adduction Moment Impulse (Nm.s/BW*ht)0.53 (-1.14, 2.20)0.79 (-3.57, 5.15)0.530.720.48 (-1.29, 2.25)1.02 (-3.47, 5.51)0.590.650.50 (-1.29, 2.28)1.06 (-3.46, 5.58)0.580.64Average weekly pain when walkingPeak Knee Adduction Moment (Nm/BW*ht%)Knee Adduction Moment Impulse (Nm.s/BW*ht)0.22 (-0.17, 0.61)0.51 (-0.52, 1.53)0.270.330.24 (-0.18, 0.65)0.58 (-0.47, 1.63)0.260.290.24 (-0.17, 0.66)0.60 (-0.46, 1.65)0.250.26Average weekly painPeak Knee Adduction Moment (Nm/BW*ht%)Knee Adduction Moment Impulse (Nm.s/BW*ht)0.07 (-0.32, 0.45)0.07 (-0.83, 1.06)0.740.890.13 (-0.27, 0.54)0.18 (-0.83, 1.20)0.520.720.15 (-0.26, 0.55)0.21 (-0.81, 1.23)0.480.68Average weekly restriction to activitiesPeak Knee Adduction Moment (Nm/BW*ht%)Knee Adduction Moment Impulse (Nm.s/BW*ht)0.17 (-0.20, 0.54)0.21 (-1.18, 0.76)0.270.330.22 (-0.17, 0.61)0.33 (-0.66, 1.33)0.260.510.23 (-0.16, 0.62)0.35 (0.65, 1.35)0.250.49* adjusted for age, gender, body mass index** adjusted for age, gender, body mass index, treatment group Open table in a new tab