Male subjects with early-stage knee osteoarthritis do not present biomechanical alterations in the sagittal plane during stair descent

Patients with osteoarthritis (OA) of the knee show a loss of functional independence due to difficulty performing tasks that require high demand of the knee joint, such as descending stairs. However, it is unclear how muscular and biomechanical changes were present in patients with OA in the early stages. Thus, the purpose of this study was to analyze the kinetics, kinematics and muscle activation of men with early-stage knee OA during stair descent and compare them with a healthy control group. We evaluated 31 volunteers who were divided into two groups. The Osteoarthritis Group (OAG) included 17 men with grade I or II knee OA (53 ± 6 years) and the Control Group (CG) included 14 healthy men (50 ± 6 years). We performed a kinematic evaluation of stair descent in the sagittal plane in order to analyze knee flexion angles. Electromyography (EMG) of the vastus lateralis muscle was also performed and the vertical ground reaction force was measured. The WOMAC questionnaire was administered to all volunteers. Statistical analysis consisted of the nonparametric Mann-Whitney U test for intergroup comparisons of all variables (p > 0.05). There were no significant kinematic, kinetic or EMG differences between groups. For the WOMAC, the intergroup differences were significant in all three sections (pain: p = 0.001, stiffness: p = 0.008 and function: p = 0.0005). In men with knee OA grade I or II, the stair decent is preserved in the sagittal plane, indicating that at these stages of the disease the functional adaptations are not expressed.