BACKGROUND AND OBJECTIVE: Reduced joint proprioception plays an important role in the initiation and progression of the knee osteoarthritis. The present study aims to evaluate postural sway in three different positions and analyze its trends using relative indices.
METHODS: This cross-sectional study was conducted among 34 patients with knee osteoarthritis and 12 healthy people using selective sampling and convenience sampling. In order to evaluate the static equilibrium indices, patients were asked to sit on the force plate in three positions; Comfort Double Leg Standing (CDLS), Romberg Standing (RS) and Near Tandem Standing (NTS). The relative values of   and  were used to determine the changes in postural sway in RS and NTS positions relative to CDLS.
FINDINGS: In CDLS position, the range and the standard deviation of lateral position in patients (0.019 ± 0.010 and 0.003±0.001, respectively) was lower than healthy people (0.051 ± 0.039 and 0.012 ± 0.010, respectively). In this position, the displacement range in the anterior-posterior direction in patients (0.110 ± 0.029) was also lower than healthy people (0.130 ± 0.027). In RS position, standard deviation and the velocity of center of pressure displacement in the patients group (0.016 ± 0.006 and 0.012 ± 0.004, respectively) was significantly higher than healthy people (0.012 ± 0.003 and 0.009 ± 0.002, respectively). On the contrary, the ratio of  and values was higher in patients group.
CONCLUSION: Results of the study demonstrated that patients with more difficult positions (RS, NTS) have more sways than those with CDLS, especially in the lateral direction. Therefore, balancing and strengthening exercises are especially important in the lateral direction and in challenging situations.