Effect of functional weightbearing versus non-weightbearing quadriceps strengthening exercise on contact force in varus-malaligned medial knee osteoarthritis: A secondary analysis of a randomized controlled trial.

BACKGROUND: Knee osteoarthritis progression may be related to altered knee loads, particularly in those with varus malalignment. Using randomized controlled trial data, this secondary analysis of complete datasets (n = 67) compared the effects of a functional weightbearing (WB) and non-weightbearing quadriceps strengthening exercise (NWB) program on measures of medial tibiofemoral joint contact force (MTCF) during walking. METHODS: Participants aged ≥50 years and with medial knee osteoarthritis and varus malalignment were randomly allocated to a 12-week, home-based, physiotherapist-prescribed exercise program comprised of WB exercises (n = 31), or NWB exercise (n = 36). Three-dimensional lower-body motion, ground reaction forces, and surface electromyograms from six lower-limb muscles were acquired during walking at baseline and at 12-weeks follow-up. An electromyogram-informed neuromusculoskeletal model estimated bodyweight (BW) normalized MTCF (peak and impulse), including external and muscular contributions to MTCF. RESULTS: There was no between-group difference in the change in peak MTCF (-0.02 [-0.12, 0.09] BW) or MTCF impulse (-0.01 [-0.06, 0.03] BW·s). There was a between-group difference in the muscle contribution to peak MTCF (-0.08 [-0.15, -0.00] BW) and MTCF impulse (-0.04 [-0.08, -0.00] BW·s), whereby the muscle contribution reduced more in the NWB group over time compared to the WB group. There was also a between group-difference in the external contribution to peak MTCF (0.09 [0.01, 0.18] BW), but this reduced more in the WB group than in the NWB group. CONCLUSIONS: Our findings suggest no difference in MTCF between the two exercise programs, but differences in the contribution to MTCF between the two exercise programs were observed in those with medial knee osteoarthritis and varus malalignment.

Muscle Forces during Weight-Bearing Exercises in Medial Knee Osteoarthritis and Varus Malalignment: A Cross-Sectional Study.

PURPOSE: This study aimed to test the hypothesis that common weight-bearing exercises generate higher lower-limb muscle forces but do not increase medial tibiofemoral contact force (MTCF) when compared with walking in people with medial knee osteoarthritis and varus malalignment. METHODS: Twenty-eight participants 50 yr or older with medial knee osteoarthritis and varus malalignment were recruited from the community. Three-dimensional lower-body motion, ground reaction forces, and surface EMG from 12 lower-limb muscles were acquired during five squat, lunge, single-leg heel raise, and walking trials, performed at self-selected speeds. An EMG-informed neuromusculoskeletal model with subject-specific bone geometry was used to estimate muscle forces (N) and body weight (BW)-normalized MTCF. The peak forces for muscle groups (knee extensors, knee flexors, ankle plantar flexors, and hip abductors) and peak MTCF were compared with walking using a multivariate analysis of variance model. RESULTS: There was a significant main effect ( P < 0.001). Post hoc tests (mean difference (95% confidence intervals)) showed that, compared with walking, participants generated higher peak knee extensor and flexor forces during squatting (extensor: 902 N (576 to 1227 N), flexor: 192 N (9.39 to 375 N)) and lunging (extensor: 917 N (604 to 1231 N), flexor: 496 N (198 to 794 N)), and lower peak hip abductor force during squatting (-1975 N (-2841 to -1108 N)) and heel raises (-1217 N (-2131 to -303 N)). Compared with walking, MTCF was lower during squatting (-0.79 BW (-1.04 to -0.53 BW)) and heel raises (-0.27 BW (-0.50 to -0.04 BW)). No other significant differences were observed. CONCLUSIONS: Participants generated higher peak knee flexor and extensor forces during squatting and lunging but did not increase peak MTCF compared with walking. Clinicians can use these findings to reassure themselves and patients that weight-bearing exercises in these positions do not adversely increase forces within the osteoarthritic joint compartment.

Effect of exercise on knee joint contact forces in people following medial partial meniscectomy: A secondary analysis of a randomised controlled trial.

BACKGROUND: Arthroscopic partial meniscectomy may cause knee osteoarthritis, which may be related to altered joint loading. Previous research has failed to demonstrate that exercise can reduce medial compartment knee loads following meniscectomy but has not considered muscular loading in their estimates. RESEARCH QUESTION: What is the effect of exercise compared to no intervention on peak medial tibiofemoral joint contact force during walking using an electromyogram-driven neuromusculoskeletal model, following medial arthroscopic partial meniscectomy? METHODS: This is a secondary analysis of a randomized controlled trial (RCT). 41 participants aged between 30-50 years with medial arthroscopic partial meniscectomy within the past 3-12 months, were randomly allocated to either a 12-week, home-based, physiotherapist-guided exercise program or to no exercise (control group). Three-dimensional lower-body motion, ground reaction forces, and surface electromyograms from eight lower-limb muscles were acquired during self-selected normal- and fast-paced walking at baseline and follow-up. An electromyogram-driven neuromusculoskeletal model estimated medial compartment contact forces (body weight). Linear regression models evaluated between-group differences (mean difference (95% CI)). RESULTS: There were no significant between-group differences in the change (follow-up minus baseline) in first peak medial contact force during self-selected normal- or fast-paced walking (0.07 (-0.08 to 0.23), P = 0.34 and 0.01 (-0.19 to 0.22), P = 0.89 respectively). No significant between-group difference was found for change in second peak medial contact force during normal- or fast-paced walking (0.09 (-0.09 to 0.28), P = 0.31 and 0.02 (-0.17 to 0.22), P = 0.81 respectively). At the individual level, variability was observed for changes in first (range -26.2% to +31.7%) and second (range -46.5% to +59.9%) peak tibiofemoral contact force. SIGNIFICANCE: This is the first study to apply electromyogram-driven neuromusculoskeletal modelling to an exercise intervention in a RCT. While our results suggest that a 12-week exercise program does not alter peak medial knee loads after meniscectomy, within-participant variability suggests individual-specific muscle activation patterns that warrant further investigation.