Effect of an ankle–foot orthosis on gait parameters in medial knee osteoarthritis: A single-subject study

This single-subject study evaluated the immediate, mid-term (with AFO after six weeks), and therapeutic (without AFO after six weeks) effects of an ankle-foot orthosis (AFO) with a Klenzak joint and lateral cuff on gait in women with medial knee osteoarthritis (KOA). Five participants were analyzed using a 3D motion analysis system and force plate. Kinetic variables included the external knee adduction moment (EKAM), external knee flexion moment (EKFM), center of pressure (COP) displacement, and spatiotemporal parameters (cadence, stride length, speed). Descriptive statistics and individual effect sizes were used. Immediately, the AFO caused a lateral COP shift (high effect sizes in 4/5 participants) and reduced the first peak EKAM in three participants. After six weeks, mean EKAM and EKFM increased, showing variable individual responses. Therapeutically, the first peak EKAM decreased again in three participants. Most participants showed improvements in spatiotemporal parameters across evaluations. The most consistent biomechanical benefits were found in participants with neutral foot posture. These findings suggest that the AFO may offer immediate and therapeutic benefits for knee loading and gait in some individuals with KOA. However, mid-term reduction in effectiveness indicates the possible need for orthosis readjustment.