Abstract
Purpose
Whether the presence of knee effusion in individuals with knee osteoarthritis (OA) affects periarticular neuromuscular control during gait and thus the joint loading environment is unknown. The purpose was to test the hypothesis that knee effusion presence alters periarticular neuromuscular patterns during gait in individuals with moderate knee OA.
Method
40 patients with medial compartment knee OA participated after giving informed consent. Patients were assessed for the presence of effusion using a brush test and were assigned to the knee effusion (n=20) and no knee effusion (n=20) groups. Surface electrodes were placed in a bipolar configuration over the lateral and medial gastrocnemius, vastus lateralis and medialis, rectus femoris and the lateral and medial hamstrings of the affected limb. Five trials of self-selected walking were completed. Electromyograms (EMG) were collected using an AMT-8 EMG system (Bortec Inc.). An Optotrak motion capture system (Northern Digital Inc.) recorded leg motion. Euler rotations were used to derive knee angles. EMG waveforms were low-pass filtered and amplitude normalized to maximal effort voluntary isometric contractions. Quadriceps, gastrocnemius and hamstring strength was measured from torques produced against a Cybex dynamometer. Principal Component Analysis extracted the predominant waveform features and weighting scores were calculated for each measured waveform. Analysis of variance models test for main effects (group, muscle) and interactions (alpha = 0.05). Bonferonni post hoc testing was employed.
Results
No 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). Gastrocnemius activation was not influenced by the presence of effusion (p>0.05). For individuals with effusion, a greater overall quadriceps activation was found and a prolonged hamstring activation into mid-stance only (p<0.05). Range of motion excursion from heel strike to peak extension during terminal stance was greater with effusion (p<0.05).
Conclusion
The hypothesis that knee effusion in those with moderate knee OA is associated with alterations in quadricep and hamstring muscle activation patterns and sagittal plane knee motion during gait was supported. Quadriceps muscle inhibition during the normalization exercises may provide a partial explanation, consistent with results from acute effusion models. However, the hamstring alteration during mid-stance only, no strength differences between the two groups and altered kinematics support that mechanisms other than muscle inhibition are responsible for the altered patterns. These novel findings are a first step at understanding the effects of knee effusion on periarticular muscle function during gait that subsequently can affect the mechanical environment of the joint in those with a more chronic effusion.
