Changes in Ankle Mechanical Stability in Those With Knee Osteoarthritis

Hubbard TJ, Hicks-Little C, Cordova M. Changes in ankle mechanical stability in those with knee osteoarthritis.

Objective

To examine ankle joint mechanical stability in patients who had mild to moderate knee osteoarthritis (OA).

Design

Case control study.

Setting

Biodynamics research laboratory.

Participants

Subjects with knee OA (n=15; 5 men and 10 women; mean age ± SD, 60.3±10.2y; mean mass ± SD, 93.9±18.3kg; mean height ± SD, 167.23±9.5cm) were matched to healthy controls (n=15; 5 men and 10 women; mean age ± SD, 59.6±12.6y; mean mass ± SD, 83.5±19.2kg; mean height ± SD, 169.7±12.6cm).

Interventions

Not applicable.

Main Outcome Measures

Mechanical ankle-subtalar joint stability was assessed with an instrumented arthrometer where ankle-subtalar joint motion for anterior/posterior displacement and inversion/eversion rotation was measured. Separate 2 × 2 mixed model analyses of variance were performed.

Results

Significant group × side interactions were observed for anterior and posterior displacement (P<.05) where patients with knee OA had significantly less anterior and posterior ankle displacement compared with the control group, as well as compared with their unaffected extremity. Additionally, patients with knee OA had significantly (P<.05) less inversion/eversion rotation than their respective controls.

Conclusions

These data suggest that altered ankle joint mechanics may be the result of deviations in ankle joint alignment secondary to the structural changes at the knee. Compensatory changes in ankle joint mechanics must also be considered when addressing lower extremity functional deficits in patients with knee OA.