Trial of Self-managed Approaches for Patellofemoral Pain Syndrome in Active Duty

The overall objective of this project is to compare the three home-managed treatment regimens for PFPS: neuromuscular electrical stimulation (NMES), transcutaneous electrical nerve stimulation (TENS), and NMES combined with TENS to a standard home exercise program (HEP). Each of the three treatment arms will be supplemented by HEP and compared to a group receiving standard HEP alone. The central hypothesis is that the combination of NMES with TENS will show significantly greater improvements in muscle strength, mobility, pain, daily activity and quality of life (QOL) than HEP alone.

The investigators are examining: 1) whether the three treatment regimens are significantly more efficacious than standard HEP alone in improving lower extremity muscle strength, physical activity, mobility, pain, and quality of life; 2) lower extremity muscle strength, physical activity, mobility, pain, and quality of life differ significantly across the 4 time periods; 3) is there an interaction between treatment and time in relation to lower extremity muscle strength, physical activity, mobility, pain, and quality of life.

Patellofemoral pain syndrome (PFPS) is the most common diagnosis among active duty military presenting with knee pain in the military ambulatory care setting. The incidence of PFPS has shown a striking increase of \>11.3% over the last 4 years, affecting work performance, limiting activity, and impacting military deployment health. The investigators have shown that home-based neuromuscular electrical stimulation (NMES) is safe, portable, easy-to-use and improves quadriceps muscle strength with some pain relief. NMES and transcutaneous electrical nerve stimulation (TENS) devices are widely used by warfighters in the theatre of operation for knee problems. The overall objective of this project is to compare three home-managed treatment regimens for PFPS: NMES, TENS, and NMES combined with TENS to a standard home exercise program (HEP). The central hypothesis is that the combination of NMES with TENS will show significantly greater improvements in muscle strength, mobility, pain, daily activity and quality of life (QOL) than HEP alone. The rationale for this study is that increasing muscle strength and decreasing pain will significantly improve mobility, physical activity and QOL. Such outcomes will ultimately result in improved deployability, retention of military personnel and decreased economic costs in this population. The specific aims are to determine whether the three treatment regimens are significantly more efficacious than standard HEP for improving muscle strength, physical activity, mobility, QOL and symptoms of PFPS including pain. After consent and baseline testing, the investigators will randomly assign active duty male and female subjects, ages 18 to \<45, (n=136) with PFPS to one of the four groups. Each of the three treatment arms will be supplemented by HEP and compared to a group receiving standard HEP alone. All groups will receive 9 weeks of home therapy. Using GEE methods, the investigators will build longitudinal regression models so that differences in time trends for the outcome variables among controls and those in the treatment groups can be statistically assessed. Positive results could translate into accelerated rehabilitation, decreased symptoms and lower medical costs with better patient outcomes.

Eligibility Criteria:
Inclusion Criteria:

The study will be open to all active duty personal who are:

1. diagnosed with knee pain, categorized as anterior or retropatellar in one or both knees;
2. self-reported difficulty performing at least two or more of the following activities associated with knee pain: prolonged sitting, stair climbing, running, jumping and repetitive movements such as kneeling or squatting or stooping;
3. military service member at the time of diagnosis;
4. age ≥18 and \<45 years; and
5. ability to provide freely given informed consent.

Exclusion Criteria:

Those who might be at risk of adverse outcomes from the study interventions will be excluded. This includes individuals with

1. Fracture or injury to external knee structures such that knee extension or flexion is impaired;
2. A significant co-morbid medical condition (such as severe hypertension, neurological disorder or pacemaker/defibrillator) in which NMES strength training or unsupervised exercise is contraindicated and would pose a safety threat or impair ability to participate;
3. Previous knee surgeries (i.e., tibiofemoral, patellofemoral) excluding knee arthroscopy;
4. Knee instability or recurrent patella dislocation or subluxation;
5. Inability or unwillingness to participate in a home exercise program or strengthening program;
6. Inability to speak and/or read English;
7. Reduced sensory perception in the lower extremities;
8. Pregnancy;
9. Vision impairment, where participant is classified as legally blind;
10. Unwillingness to accept random assignment; or
11. A score of 23 or greater on the Center for Epidemiological Studies-Depression scale (CES-D).