Effects of joint effusion on quadriceps muscles in patients with knee osteoarthritis

• We investigated the effect of 20 ml effusion on the knee extensors in OA patients.
• The primary aim was to evaluate the effect on the peak torque of knee extensor muscles, with the secondary aim to examine the RMS values of the vastus medialis and lateralis muscles.
• 20 ml joint effusion did not change peak torque and RMS values.

ObjectivesTo evaluate the effect of knee effusion on the quadriceps muscle in patients with knee osteoarthritis (OA).DesignSingle-blind, randomized, controlled clinical trial.SettingSingle medical center.ParticipantsForty subjects with knee OA were assigned to a experimental (n = 20) or control (n = 20) group.Main outcome measuresQuadriceps torque and root mean square (RMS) values of surface electromyography (EMG) of the vastus medialis and vastus lateralis muscles were measured during a maximal isometric contraction at 60° knee flexion. Thereafter, 20 mL of normal saline was injected into the knee joint of the experimental group. Quadriceps torque and RMS values were again measured.ResultsFive subjects did not complete the study. No significant difference in quadriceps peak torque or RMS of EMG activity was observed at baseline, pre-effusion, or post-effusion measures in either group. The experimental group showed no significant change in quadriceps peak torque or RMS of EMG activity in any period compared with the control group.ConclusionsThese results demonstrate that a 20 ml joint effusion did not affect peak torque or RMS values of the quadriceps muscle in patients with knee OA.