Knee osteoarthritis (OA) is a leading cause of disability that places an enormous economic burden on the U.S. military and healthcare system. OA prevalence is greater in Service Members than in the general population, and is the leading cause of medical separation from military service during peacetime and the second leading cause during armed conflict. Knee OA also incurs other negative health implications such as increased risks for obesity, depression, and cardiovascular disease, and is a leading cause of years of life lost due to disability.

Knee OA commonly results from knee injuries (i.e., post-traumatic osteoarthritis – PTOA). Anterior cruciate ligament injury risk is 10 times greater in Service Members compared to civilians, and incurs a high risk of PTOA with up to 80% of patients displaying PTOA within 10-15 years. The primary treatment approach, surgical reconstruction (ACLR), improves joint stability but does not mitigate PTOA risk. Furthermore, PTOA progresses rapidly, with declines in joint health evident within 1 year post-ACLR. As such, individuals with ACLR represent an ideal population for evaluating novel rehabilitation approaches for preventing PTOA.

Lingering dysfunction (e.g., weakness) of the quadriceps muscle is a nearly universal complication associated with knee injuries such as ACLR. Quadriceps dysfunction leads to changes in how patients walk (i.e., aberrant gait biomechanics) that are primary contributors to PTOA development. Therefore, improving quadriceps function and mitigating aberrant gait biomechanics is critical for successful ACLR rehabilitation and prevention of PTOA. However, current rehabilitation methods are insufficient for these purposes as evidenced by quadriceps dysfunction and aberrant gait biomechanics that persist for several years following the initial injury.

Vibration acutely improves quadriceps function and aberrant gait biomechanics in individuals with ACLR. There are two types of vibration for these purposes: whole body vibration (WBV) and local muscle vibration (LMV). We developed a prototype LMV stimulator and have demonstrated that it acutely improves quadriceps function as effectively as WBV and acutely mitigates aberrant gait biomechanics in individuals with ACLR. WBV devices are costly (as much as $15,000) and are not portable, thus limiting their clinical feasibility. However, our prototype LMV device can be produced for a much smaller cost and is portable for use in multiple settings including rehabilitation clinics, military field settings, and the patient’s home. Therefore, our LMV device may be a cost-effective alternative to WBV.

While we have demonstrated the acute effects of vibration, its longitudinal effects on outcomes linked to PTOA development are unknown. The proposed research will embed WBV and LMV in standard ACLR rehabilitation and evaluate their effects on quadriceps function, gait biomechanics, patient perceptions (e.g., quality of life), and MRI indicators of knee joint health and PTOA risk over the first year following ACLR. Demonstrating that vibration improves these outcomes would support its use in rehabilitation of knee injuries. Furthermore, demonstrating that our LMV prototype stimulator is as effective as WBV but at a lower cost and enhanced clinical feasibility would be a major advancement in knee injury rehabilitation. The proposed work will advance our preclinical findings and provide the clinical efficacy data necessary to accelerate development of our LMV stimulator as a commercially available device.

The results of the proposed research would address multiple FY20 JWMRP Focus Areas including 1) injury prevention and reduction (Military Operational Medicine Research Program) and 2) rehabilitation of neuromusculoskeletal injury (Clinical and Rehabilitative Medicine Research Program). ACLR is one of many injuries that could benefit from the proposed research. Quadriceps dysfunction and aberrant gait biomechanics are common with other knee injuries such as meniscus injuries, patellofemoral pain syndrome, and intraarticular fractures, as well as in individuals already diagnosed with knee OA, thus these patients would also be expected to benefit from the proposed interventions. Knee injuries comprise 19% of all injuries sustained during military training and 15% of all non-combat injuries during deployment. As such, the proposed investigation has the potential to impact the health and well-being of numerous Service Members and Veterans. Given the high prevalence of knee injuries in military personnel and the subsequent high risk of developing PTOA, improving methods for rehabilitating knee injuries is paramount for maintaining the combat readiness of our armed forces and preserving the health and well-being of Service Members and Veterans.