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

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. 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. The three phases of the sit-to-stand task were analyzed. During Phase1, the moderate osteoarthritis group decreased the total support moment (P = 0.012). During Phase2, 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 Phase2, 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). Those with moderate osteoarthritis showed modified sit-to-stand movement pattern. While in Phase3 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. •Those with different degrees of knee osteoarthritis rise from the chair differently.•Moderate osteoarthritis presented an intersegmental incoordination at the end of the task.•Individuals with moderate osteoarthritis stand up using higher trunk flexion.•Individuals with mild/moderate osteoarthritis stand up with lower knee moment in the sagittal plane.