A case highlighting the influence of knee joint effusion on muscle inhibition and size

The patient sustained an injury that caused knee joint effusion. The patient had undergone reconstruction of the anterior cruciate ligament on the right knee approximately 8 years before this injury.

The influence of knee joint effusion on the isometric and dynamic torque characteristics, neural drive and muscle size of the knee extensors was analyzed during the first 11 weeks of recovery. Maximum knee extensor torque and electromyographic (EMG) activity were assessed on a weekly basis. MRI scans of the thigh were taken to quantify vastus medialis muscle cross-sectional area.

Initial knee joint aspiration resulted in an 85-399% increase in isometric knee extensor torque and a 9-706% increase in vastus lateralis and vastus medialis muscle EMG activity, indicating muscle inhibition due to effusion. The knee extensors were inhibited to a greater extent in the most flexed position than in the more extended knee joint positions. After the initial aspiration, the knee extensor torque-velocity relationship increased by 56-453% with a corresponding increase in EMG activity.

Repetition of aspiration and instigation of a resistance training program resulted in the injured leg having a torque and muscle size comparable with the contralateral healthy leg 11 weeks after initiation of the rehabilitation program.