Return to sports and physical activity after implantable shock absorber surgery for patients with medial knee osteoarthritis

<h2>Abstract</h2><h3>Objectives</h3> Symptomatic knee osteoarthritis (OA) is a leading cause of disability; treatment options appropriately focus on a return to active lifestyle. Procedures such as high tibial osteotomy (HTO) and knee arthroplasty can deliver excellent outcomes, but are complicated by high rates of morbidity, long recovery times, and limitations on post-recovery physical activities. This study assesses the postoperative activities of patients with medial knee OA treated with an implantable shock absorber (ISA), a device that is intended to bridge the treatment gap by allowing faster return to a higher level of function with less surgical morbidity without ruling out future procedures. Treatment with the ISA includes a post-operative prescription permitting and encouraging full weight bearing and unrestricted range of motion immediately post-surgery. We hypothesize this has implications for the active working-age patient with respect to return to activities requiring normal knee function. <h3>Materials and Methods</h3> In this prospective open-label trial, subjects with symptomatic unilateral medial knee OA (Kellgren-Lawrence grades 1-4) were treated with an ISA device; 99% had post-procedure physical therapy. Subjects rated their limitations due to OA regarding physical activities that were important to them (e.g., cycling, running, walking) on a five-point scale modeled after the Knee Society Score (KSS) Discretionary Knee Activities section (from ‘no limitation' to ‘cannot do') at baseline and through 24 months after ambulatory surgical application of the ISA. Patients also rated their sports and recreation function and the degree to which their treated knee feels "normal". <h3>Results</h3> Complete datasets were available from 73 of 81 (91%) study participants regarding 219 rated activities. At baseline, 1.8% of desired activities could be performed with minimal or no limitation, while at 24 months, 64.4% of desired activities could be performed post-operatively with minimal or no limitation (p<0.0001). This trend was consistent across types of activities, and included those with high impact, strength, and flexibility demands. Sports and recreation function on the Knee Injury and Osteoarthritis Outcome Score (KOOS) scale improved from a mean of 13.8 at baseline to 62.3 at 24 months (p<0.0001). Furthermore, 69% of subjects stated that their knee ‘never' felt normal at baseline, and this decreased to 19% at 24 months (p<0.0001). <h3>Conclusions</h3> Treatment with ISA removed many of the limitations on physical activities that subjects with symptomatic knee OA experienced, and made knees feel more normal. This may be because treatment with ISA allows nearly immediate return to full weight-bearing and has no device-related activity restrictions. As such, ISA represents an important and proven therapeutic option that typically provides symptomatic relief as well as a return for most of activity goals.