Electrical Stimulation Not Effective for Patellofemoral Pain SyndromeThe patella, or kneecap, can be a source of knee pain when it fails to function properly. Alignment or overuse problems of the patella can lead to pain, weakness, and swelling of the patellofemoral joint. This problem is called patellofemoral pain syndrome (PFPS). PFPS is most common among athletes, especially teens and young adults.
Many studies have shown exercise works to help PFPS. Other studies have used electrical muscle stimulation (EMS) to help with knee problems such as osteoarthritis, painful sports injuries, and after knee surgery. In this study, physicians from the Medical University of Vienna test to see if EMS might help with PFPS.
All patients included had bilateral knee pain associated with PFPS. They were divided up into two treatment groups. Group one followed an exercise program outlined by a physical therapist. Group two had the same exercises and EMS. Both groups were treated for 12 weeks.
Daily exercises included trunk and leg isometric, concentric, and eccentric strengthening. Functional activities such as stepping, squatting, and balance training were also included as part of the exercise training program.
The therapist progressed each patient's exercise program according to his or her pain levels. Stretching of the calf and thigh muscles were done at the end of each training session. A special appendix at the end of the article provided detailed information of the daily and weekly progression of the training program.
For group two, EMS electrodes were used to stimulate contraction of the quadriceps muscle. A twice-daily program of 20 minutes self-stimulation was used by the patients at home. The stimulation intensity was kept as high as the patient could comfortably tolerate.
Results were measured at the end of the three months training period. Pain levels, function (Kujala patellofemoral test), and muscle strength were the main outcome measures. Strength was tested using an isometric contraction. A special chair was specifically designed to conduct strength testing in the seated position.
There was no difference between the two groups at the end of three months. Pain levels were decreased and function improved in both groups. And the improvements remained for over a year even after the programs were stopped.
Exercise was the main reason patients improved. There did not appear to be any added benefit from doing EMS along with exercise for PFPS. The results of this study support the previously reported idea that increasing extensor strength and balancing the quadriceps muscle inhibits knee pain.
But they found something else of interest. Pain relief didn't occur because of improved muscle strength. The strength values of the quadriceps muscle (isometric contractions) did not increase as a result of the training program.
It's likely that the changes occurred as a result of neurophysiologic changes, rather than any increase in strength. If that is true, then it is possible the EMS had a role in improving the timing and activation pattern of the quadriceps muscle. The authors suggest further studies to look at (and compare) the potential of neurophysiologic effects of exercise versus EMS.
Walter Bily, MD, et al. Training Program and Additional Electrical Muscle Stimulation for Patellofemoral Pain Syndrome: A Pilot Study. In Archives of Physical Medicine and Rehabilitation. July 2008. Vol. 89. No. 7. Pp. 1230-1236.
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