Reducing Postoperative Knee Flexion Contracture Recurrence by Correcting Leg Length Discrepancy in the Non-surgical Knee in Patients Undergoing Total Knee Arthroplasty for Primary Osteoarthritis: A Feasibility Study

Joint contractures are characterized by a restriction in the full passive range of motion (ROM) of a joint and are a major burden on public health. They restrict mobility, have a negative impact on quality of life, limit an individual's productivity and earning potential, and can prevent basic activities of daily living such as dressing and eating. The geriatric population is particularly vulnerable to contractures due to accumulated comorbidities leading to restricted joint movement and permanent loss of ROM.

A knee flexion contracture (KFlC) is a limitation in knee extension. Patients with KFlCs limp and are afflicted with a constant enhanced energy demand on the quadriceps muscle, putting them at higher risk for falls and injury. Walking is slow and abnormally tiring for those with KFlC such that patients may choose to walk less or not at all. Murphy et al. identified a significant increase in energy cost of walking with a KFlC of ≥15°. In addition, KFlCs cause a functional shortening in the affected limb resulting in a leg length discrepancy (LLD). LLDs contribute to even greater energy requirements for ambulation, worse pain due to premature joint wear, and are associated with knee osteoarthritis progression. One study identified shoe modification as a means of correcting this treatable risk factor. To the investigators' knowledge, no study has examined the effect of shoe modification on KFlC.

Contractures are associated with many conditions including arthritis. In the setting of osteoarthritis (OA), the most common arthritis and a world-leading cause of disability in the elderly, contractures are highly prevalent: over one third of 3,400 patients with OA presenting for total knee arthroplasty (TKA) had a KFlC. The burden of KFlC in OA is further compounded by the pre-operative contracture putting the patient at a higher risk for contracture, knee pain and poor outcome post-operatively. Loss of pre-operative ROM was found to be the best predictor of lost post-operative ROM.

During TKA, surgeons are often able to restore some or all knee ROM which transiently eliminates the contracture in the immediate post-operative period. Unfortunately, full ROM is lost over time in a notable proportion of patients. The overall incidence of KFlC following TKA has been reported to be between 1 to 5%. In patients with pre-operative KFlC, this has been reported as high as 15% with the resulting post-operative KFlCs still present at 3-year follow-up4. Patients who develop post-operative KFlC report less satisfaction, poorer function and more pain post-surgically. Post-operative loss of ROM has been described as one of the most common causes of readmission within the first 90 days after surgery and was identified as being the primary reason for nearly 20% of revision TKAs. These large percentages represent a significant number considering that 719,000 replacements were performed in the USA in 2010 and that the Ottawa hospital alone performs over 500 TKAs per year. KFlCs therefore contribute to increased health care costs.

Treatment of KFlC includes aggressive physiotherapy, therapeutic modalities, continuous passive ROM devices, bracing, manipulation under anesthesia, arthroscopy, open arthrolysis, or TKA revision surgery. Despite these numerous and costly options however, treatment is often unrewarding. Overall, contractures draw heavily on health care resources because of their chronic nature and poor response to treatment.