As of September 1, 2014, 1,573 US Military servicemembers have sustained a major limb amputation since 2001. In addition to the inherent mobility challenges posed by amputation, this population suffers from a variety of comorbidities, including osteoarthritis (OA). Osteoarthritis is the primary source of long-term disability in wounded servicemembers and the inability to return to active duty following traumatic injury. Osteoarthritis of the knee specifically is among the most prevalent and costly chronic diseases in the USA. The estimated lifetime incidence rate of knee OA among all American adults ages 25+ is at least 14%. Knee OA, particularly on the medial knee joint, is the most common form of OA and the leading cause of mobility impairment in older adults.

The risk of knee OA in the intact limb is especially concerning for young service members with amputations. At Walter Reed National Military Medical Center (WRNMMC), service members with amputations are treated by a large multidisciplinary team through physical and occupational therapy, prosthesis fitting and training, and gait and motion analysis, with generally successful outcomes, and advances in prosthesis technology have greatly improved the mobility of amputees and their ability to engage in physical activity. However, very little is currently done towards the objective of preventing knee OA, and the incidence and prevalence of chronic comorbidities in amputees remain high. Most servicemembers with amputations are relatively young when they receive their injuries and will live with any associated disabilities for many years. The incidence of knee OA increases with age and typically peaks at around 60 years old. Service members with amputations will thus live with a substantial and progressive risk of knee OA for many years.

In order to ultimately reduce the prevalence and healthcare burden of knee OA among servicemembers with amputations and salvaged limbs, we must first gain a better understanding of the mechanisms that increase knee OA risk in this population. This knowledge will facilitate development and evaluation of more effective preventive therapies for avoiding detrimental knee joint loading while maintaining a high level of mobility in service members with amputations.

The objective of this study is to develop clinical guidelines for using instrumented gait analysis and biomechanical modeling as a diagnostic tool for assessing knee OA risk in service members with unilateral amputation or limb salvage.