The aim of this study was to find out the effect of specific Watsu program on range of motion and relieving of chronic pain in people with osteoarthritis of the knee and hip. 30 male with osteoarthritis between the ages of 50-55 years were selected as subjects. They were divided into two groups: group I or experimental group (n = 15), and group II or control group (n = 15). The first group underwent a specific Watsu® Therapy program for eight weeks, two days/week and 45 min/per session in water. Group II - performed no specific exercise program. Pre and post-tests were conducted on the flexibility test for lower limb and relief of chronic pain by a questionnaire Pain Catastrophizing Scale designed to determine the decrease of pain threshold on the functional score. Physical activity level is measured by 1-mile walk time. Mean, standard deviation, and t test were used to analyze the data and percentages were calculated for the pain relief. The results showed positive results on the peak torque, torque development rate and functional test were similar between groups before exercise program. A peak torque increase (P < 0.05) was found in hip extension, hip flexion and plantar flexion in the experimental group. The peak torque of knee flexion & extension and ankle dorsiflexion did not differ between groups in post training assessment (P >.05). No changes were found in the control group (P >0.05). As far as the decrease of pain threshold is concerned, the experimental group had a 60% reduction in functional score compared to the control group, which had only a 15% score. It was concluded that specific Watsu training has a beneficial effect on the flexibility of the experimental group in three parts of the body and has a reduction in pain of more than normal range indicating that the above training is highly effective in rehabilitation of osteoarthritis.