Knee effusion affects knee mechanics and muscle activity during gait in individuals with knee osteoarthritis

SummaryObjectiveTo test the hypothesis that knee effusion presence in those with knee osteoarthritis (OA) alters knee joint muscle activation patterns and sagittal plane mechanics during gait.MethodsThirty-five patients with medial compartment knee OA were assessed for the presence of effusion using a brush test. Based on the results, they were assigned to the knee effusion (n = 17) and no knee effusion (n = 18) groups. Electromyograms from seven lower extremity muscles (lateral and medial gastrocnemius, vastus lateralis and medialis, rectus femoris and the lateral and medial hamstrings), leg motion and ground reaction forces were recorded during self-selected walking. Isometric knee extensor, plantar flexor and knee flexor strength were measured. Discrete measures from angular knee motion and net external moment of force waveforms were identified. Principal component analysis extracted electromyographic waveform features. Analysis of variance models tested for main effects (group, muscle) and interactions (α = 0.05). Bonferroni post-hoc testing was employed.ResultsNo differences in age, body mass index, knee pain, Western Ontario McMaster Osteoarthritis Index scores, gait velocity and muscle strength were found between groups (P > 0.05). Individuals with effusion had a greater overall quadriceps activation and prolonged hamstring activation into mid-stance (P < 0.05). Knee joint flexion angles were higher (P < 0.05) and net external knee extension (KE) moments in mid to late stance lower in the effusion group.ConclusionQuadriceps and hamstrings activation during walking were altered when effusions were present. Increased knee flexion (KF) angles and decreased KE moment in mid-late stance provide a mechanical explanation for the effect of joint effusion on muscle activation in those with knee OA

Foot progression angle and the knee adduction moment: a cross-sectional investigation in knee osteoarthritis

SummaryObjectiveTo test the hypothesis that an association exists between the characteristics of the knee adduction moment and foot progression angle (FPA) in asymptomatic individuals and those with mild to moderate and severe knee osteoarthritis (OA).DesignFifty asymptomatic individuals, 46 patients with mild to moderate and 44 patients with severe knee OA were recruited. Maximum knee adduction moment during late stance and principal component analysis (PCA) were used to describe the knee adduction moment captured during gait. Multiple regression models were used for each of the three group assignments to analyze the association between the independent variables and the knee adduction moment.ResultsFPA explained a significant amount of the variability associated with the shape of the knee adduction moment waveform for the asymptomatic and mild to moderate groups (P<0.05), but not for the severe group (P>0.05). Walking velocity alone explained significant variance associated with the shape of the knee adduction moment in the severe OA group (P<0.05).ConclusionA toe out FPA was associated with altered knee adduction moment waveform characteristics, extracted using PCA, in asymptomatic individuals and those with mild to moderate knee OA only. These findings are directly implicated in medial knee compartment loading. This relationship was not evident in those with severe knee OA