Background: Osteoarthritis is the most common type of arthritis in middle aged and older people. It often occurs in weight bearing joints, such as knee and hip. The pain may limit ability to get up from a chair, stand and walk or climb stairs. The pain tends to get worse with activity, so that pain is worst at the end of the day. Treatment is aimed mainly at relieving symptoms and maintaining functions. Treatments include simple painkiller drugs, weight loss if needed, physical therapy and regular exercise. In addition, strengthening the muscles around affected joints may help relieving pain and improve functions in short term. The actual relationship between muscle strength and the course of the disease itself, however is not clear.

Methodology: 20 subjects, aged 40-80 years with unilateral knee pain due to according to Grade 1, 2 or 3 (Kellgren-Lawrence grading system of osteoarthritis) osteoarthritis and pain symptoms provoked by activity for at least 6 months were included in the study. After the initial assessment using Visual Analogue Scale (VAS) for pain and Manual Muscle Testing (MMT) for Quadriceps muscle strength of affected side at 0^th week, the subjects were randomly divided into 2 equal Groups (Group A & B) with each group consisting of 10 subjects. The subjects in Group A were given Isometric exercises of knee joint. The subjects in Group B were administered with Ultrasound Therapy. The treatment duration was 4 weeks. Pain and quadriceps muscle strength of affected knee joint was re-assessed using VAS and MMT respectively at the end of each week (i.e. 1^st, 2^nd, 3^rd, 4^th week).