Effect of degree of knee osteoarthritis on balancing capacity after sudden perturbation

This study aimed to assess equilibrium ability after sudden perturbation in patients with moderate and severe unilateral knee osteoarthritis (OA), with regard to age, gender, and lateral dominance. Our clinical trial included 45 female and 45 male healthy elderly subjects, 24 female and 24 male patients with moderate OA (mOA), and 24 female and 24 male patients with severe OA (sOA). Subjects were divided in two age groups: 65-69 and 70-74years. Using an oscillatory platform, we conducted provocation tests and determined the Lehr's damping ratio (D), which represents balancing capacity after sudden perturbation. D values determined for standing on both legs were similar to those of healthy individuals on the dominant limb or for OA patients on the non-affected limb; they were significantly lower for healthy individuals on the non-dominant limb and OA patients on the affected limb. For healthy subjects and mOA patients, D was significantly decreased with age and influenced by gender. sOA patients presented lower D values than other groups under all conditions, which were not influenced by age or gender. Our results demonstrate that OA patients were less capable of responding to perturbations, possibly indicating that they have an increased risk of falling.