Individual joint contributions to the total support moment during the sit-to-stand task differentiate mild and moderate knee osteoarthritis.

BACKGROUND

Knee osteoarthritis tends to modify the kinematics and kinetics of the sit-to-stand task. However, it is not clear whether the different degrees of knee osteoarthritis differentiate regarding these aspects. The objective was to identify if the trunk flexion, lower limb kinetics, total support moment, and individual joint contributions to the total support moment during the sit-to-stand task are different between patients with mild and moderate knee osteoarthritis.

METHODS

Sixty-two participants were grouped as follows: moderate knee osteoarthritis (n = 16), mild knee osteoarthritis (n = 25), and controls (n = 21). The participants performed a sit-to-stand task, which was analyzed using a 3D-motion system and a force plate.

FINDINGS

The three phases of the sit-to-stand task were analyzed. During Phase, the moderate osteoarthritis group decreased the total support moment (P = 0.012). During Phase, the moderate osteoarthritis group showed higher trunk flexion (P = 0.023) and lower internal hip and knee extension moments (P ≤ 0.001 and P ≤ 0.040, respectively) when compared to controls. Also in Phase, both the mild and moderate groups used lower total support moment (P = 0.019, and P ≤ 0.001, respectively). When compared to the controls and mild osteoarthritis group those with moderate osteoarthritis presented higher hip joint contribution to the total support moment (P ≤ 0.001 and P = 0.006, respectively) as well as lower knee joint contribution (P ≤ 0.003 and P = 0,013, respectively).

INTERPRETATION

Those with moderate osteoarthritis showed modified sit-to-stand movement pattern. While in Phase a higher contribution of the hip joint to the total support moment was observed, during previous phases the individuals were able to decrease the load on the knee without influencing the lower limb load distribution.