Osteoarthritis (OA) is one of the most common joint diseases causing pain, muscle weakness and disability in older population. Quadriceps muscle weakness is one of the recognized risk factors for the development and the progression of the disease. Increasing the muscle strength could actually bring many benefits to the knee OA patients. The purposes of this study are 1) to investigate the effects of combining the EMG biofeedback technique into a stationary cycling exercise on the activities of vastus medialis (VM) in people with medial compartment knee OA; 2) To investigate the efficiency of a 6-week cycling exercise program on improving of quadriceps muscle strength and endurance, physical functions and pain in these patients and compare between the conditions of with or without EMG biofeedback; 3) To determine the relationships between the muscle activities and the kinematics of the knee joint during this cycling exercise program; and therefore to find the mechanism of the improvement on muscle activities in the intervention of cycling combining EMG biofeedback. In this study, we will enroll the knee OA patients from our hospital, and they will be randomly assigned either to the control group, who will cycle without biofeedback, or the biofeedback group, who will cycle with a real-time visual EMG biofeedback, during the six-week training program. The exercise program consisted of a 5-minute warm-up with low-resistance cycling, 30-minute moderate-resistance cycling exercise, and 5-minute cool down session. . The knee adduction angle, quadriceps strength and endurance, KOOS Chinese version, VAS scale will also be measured at baseline and after six weeks of intervention. Mixed-model repeated measure analysis of variance (ANOVA) will be used to determine if there are any differences in the kinematic, myoelectric, muscle strength and endurance. It is hoped that the results of this study could provide information regarding the proper and efficient training strategy for the OA knee patients, and deliver the concepts of proper exercise technique to enhance health in the community.

Inclusion Criteria:

• the OA knee patients are those who had medial compartment tibiofemoral osteoarthritis in either one or both of their knees, had at least a grade 2 on the Kellgren-Lawrence score, which was verified with radiographs and a diagnosis by a physician

Exclusion Criteria:

• if the participant had been diagnosed with OA in the hip or ankle joints, had a lower extremity joint replacement, had knee joint arthroscopic surgery or intra-articular injections within 3 months prior to testing, had systemic inflammatory arthritis such as rheumatoid or psoriatic arthritis, had lower back pain that referred to the lower limbs, or those who had cardiovascular disease or other risk factor which precluded participation in aerobic exercise