To investigate the therapeutic effects of different muscle-strengthening exercises on the functional status of patients with knee osteoarthritis (OA).
One hundred thirty-two patients with bilateral knee OA (Altman Grade II) were sequentially divided into 4 random groups (GI to GIV). The patients in group I received isokinetic muscle-strengthening exercise, group II received isotonic muscle-strengthening exercise, group III received isometric muscle-strengthening exercise, and group IV acted as controls. The changes of muscle power of leg flexion and extension were measured with a Kinetic Communicator dynamometer, and patients' functional status was evaluated by visual analogue scale, ambulation speed, and Lequesne index before and after treatment, and at the follow-up 1 year later.
The results showed that the patients with OA in each treated group had significant improvement in pain reduction, disability reduction, and in walking speed after treatment and at follow-up when compared with their initial status. Isotonic exercise had the greatest effect on pain reduction after treatment, and fewer participants discontinued the treatment because of exercise knee pain. Isokinetic exercise caused the greatest increase of walking speed and decrease of disability after treatment and at follow-up. The greatest muscle-strength gain in 60 degrees /second angular velocity peak torques was found in the isokinetic and isotonic exercise groups. A significant muscle-strength gain in 180 degrees /second angular velocity peak torques was found only in the isokinetic group after treatment.
Isotonic exercise is suggested for initial strengthening in patients with OA with exercise knee pain, and isokinetic exercise is suggested for improving joint stability or walking endurance at a later time.