The present study investigated whether the presence of fluid in the joint affected peak torque and the root mean square (RMS) values of surface electromyography (EMG) in patients symptomatic for osteoarthritis (OA).

Several studies have shown that knee effusion influenced quadriceps muscle activity and induced quadriceps arthrogenic muscle inhibition in normal volunteers. However, the effect of joint effusion on the quadriceps of patients with OA is controversial,and few patients with OA have been included in studies of joint effusion.

Inclusion Criteria:

• 50 years old or older with knee osteoarthritis
• knee pain without joint effusion confirmed by ultrasonography

Exclusion Criteria:

• the presence of knee joint effusion determined using US
• a history of knee injury or surgery
• a history of knee injection within 3 months
• a history of inflammatory arthritis
• taking anticoagulants
• balance or gait disturbance
• diabetes mellitus