People with knee osteoarthritis have atrophy of the muscles surrounding the knee joint. Therefore, exercise programs primarily have been focused on the strengthening of quadriceps femoris muscle (QFM). Primary aim of this systematic review was to determine which exercise increases strength of the QFM and describe the details of the training programs. Secondary aim was to determine effectiveness of strengthening of the QFM alone on pain and dysfunction in patient with knee osteoarthritis. PubMed, PEDro, and Cochrane were searched. PEDro for methodological quality of randomized controlled trials and Cochrane Collaborations' tool for risk of bias were used. A total of 1128 articles were identified from the database searches. Ten studies which were moderate-to-high level of evidence were included. In the comparison of different strengthening exercises of the QFM, significant difference was not found between training groups. However, strengthening of the QFM exercise training was superior to proprioceptive training. Additional hot packs plus shortwave diathermy or ultrasound or transcutaneous electrical nerve stimulation had superiority to isokinetic strengthening of the QFM alone. Only additional Russian electrical stimulation showed the significant difference compared with strengthening of the QFM exercise. Most of the included studies showed that strengthening of the QFM exercises has an effect on pain reduction and improvement of function. This review indicated that the strengthening of QFM training compared with other knee exercises provided muscle strengthening, pain reduction, and improved function while combination with other electrotherapy modalities or combination with Russian electrical stimulation had superiority to alone strengthening QFM training.
Keywords: Electric stimulation therapy; Exercise; Pain; Rehabilitation; Resistance training.