Electrical Stimulation Therapies for Active Duty Military with Patellofemoral Pain Syndrome: A Randomized Trial

Patellofemoral pain syndrome (PFPS) is a common musculoskeletal disorder among military service members that causes knee pain, quadriceps strength loss, and impaired motor performance in otherwise healthy individuals. PFPS poses a threat to the health, fitness, and subsequent readiness of the total force. The goal of rehabilitation for military service members with PFPS is to regain physical capacity of strength and function and to reduce pain, in order to restore readiness in this population. The randomized controlled trial reported here compared an active home exercise program (HEP) alone with three different electrical stimulation treatment regimens implemented concurrently with HEP postulated improvements in lower extremity strength and physical functional performance while also reducing pain in active duty military diagnosed with PFPS.

After baseline testing, 130 active duty military members with PFPS were randomized to 1 of 4 treatment groups: (1) neuromuscular electrical stimulation (NMES) with HEP; (2) transcutaneous electrical nerve stimulation (TENS) with HEP; (3) combined NMES/TENS with HEP; (4) active HEP only. The primary outcome measure was degree of change in knee flexion and extension strength over 9 weeks. Secondary outcomes were physical functional performance and knee pain. The primary analyses used repeated measures, linear mixed-effects models with a random effect for subject, time as a continuous variable, group as a categorical variable, and a group and time interaction to test for differences in change over time among the groups.

All three electrical stimulation treatment groups improved in knee extension strength in the PFPS limb to a greater extent than the HEP alone group over the 9-week treatment period. The NMES and NMES/TENS groups improved to a greater extent than the HEP alone group in knee flexion strength in the PFPS limb. The reported pain improved over time for all treatment groups with no significant group differences. All three stimulation groups performed better on the 6-min walk test than the HEP alone group.

The findings from this study showed that all three electrical stimulation with HEP treatment groups showed greater improvement in strength compared to the HEP alone group. These findings could offer alternative forms of rehabilitation for AD military with PFPS as these treatment regimens can be easily implemented at home station or during deployment.