Introduction. Many patients with obesity experience knee pain. Excess body weight is a modifiable risk factor for osteoarthritis (OA) and weight loss is encouraged in patients with OA. Bariatric surgery could improve or limit the progression of these conditions through significant weight loss. The Oxford Knee Score (OKS) is a validated tool in the assessment of knee replacement surgery for OA. We present a novel application of the OKS to assess knee pain & function after weight loss surgery. The primary aim of this study was to assess whether there was a significant difference in mean OKS before and 24 months after weight loss surgery. Method. Eighteen female participants were included in this study. They underwent sleeve gastrectomy or Roux-en-Y gastric bypass. Patient demographics, body mass index (BMI) and OKS were collected pre- and 24 months post operatively. Result. There was an increase in the mean OKS from 31.8 (SD 11.8) pre surgery to 36.6 (SD 12.3) at 24 months. This was statistically significant (95% CI 0.99-10.5, p=0.02). Mean BMI reduced from 46.6 kg/m. 2. (SD 5.8) to 33.0 kg/m. 2. (SD 3.5). Conclusion. A significant improvement in mean OKS was seen after weight loss surgery. These findings demonstrate an improvement in knee pain & function with weight loss. This study contributes to a larger project evaluating the kinetic and kinematic changes to walking gait from weight loss

Introduction. Weight is a modifiable risk factor for osteoarthritis (OA) progression. Despite the emphasis on weight loss, data quantifying the changes seen in joint biomechanics are limited. Bariatric surgery patients experience rapid weight loss. This provides a suitable population to study changes in joint forces and function as weight changes. Method. 10 female patients undergoing gastric bypass or sleeve gastrectomy completed 3D walking gait analysis at a self-selected pace, pre- and 6 months post-surgery. Lower limb and torso kinematic data for 10 walking trials were collected using a Vicon motion capture system and kinetics using a Kistler force plate. An inverse kinematic model in Visual 3D allowed for no translation of the hip joint centre. 6 degrees of freedom were allowed at other joints. Data were analysed using JASP with a paired samples t-test. Result. On average participants lost 28.8±7.60kg. No significant changes were observed in standing knee and hip joint angles. Walking velocity increased from 1.10±0.11 ms. -1. to 1.23±0.17 ms. -1. (t(9)=-3.060, p = 0.014) with no change in step time but a mean increase in stride length of 0.12m (SE: 0.026m; t(9)=-4.476, p = 0.002). A significant decrease of 21.5±4.2% in peak vertical ground reaction forces was observed (t(9)=12.863, p <0.001). Stride width significantly decreased by 0.04m (SE: 0.010m; t(9)=4.316, p = 0.002) along with a decrease in lateral impulse of 21.2Ns (SE: 6.977Ns; t(7), p = 0.019), but no significant difference in knee joint angles were observed. Double limb support time also significantly reduced by 0.02s (SE: 0.006s; t(9) = 3.639, p=0.005). Conclusion. The reduction in stance width and lateral impulse suggests a more sagittal compass-gait walk is being achieved. This would reduce valgus moments on the knee reducing loading in the medial compartment. The reduction in peak ground reaction force would reduce knee contact forces and again potentially slow OA progression

The prevalence of Class III Obesity (BMI ≥ 40 kg/m25) in black women is 18%, three times the 6 national average. Class III obesity is associated with mobility limitations, particularly hip joint 7 deterioration. Therefore black women are highly likely to come to the attention of orthopedic 8 surgeons. Weight loss associated with bariatric surgery should lead to enhanced success of hip 9 replacements. However, we present a case of a black woman who underwent Roux-en-y gastric 10 bypass with the expectation that weight loss would improve her ambulation and if necessary 11 make her a better surgical candidate for hip replacement. Her gastric bypass was successful as her BMI declined from 52.0 kg/m2 to 33.7 kg/m212. However, her hip circumference post weight 13 loss remained persistently high. As a consequence, the soft tissue tunnel geometry presented 14 major challenges. The tunnel depth as well as the immobility of the soft tissue envelope 15 interfered with retractor placement, tissue reflection and adequate surgical access to the 16 acetabulum. Therefore a traditional cup placement could not be achieved. Instead, a 17 hemiarthroplasty was performed. Her pre-surgery Harris Hip Score was 17.0. In the first few 18 months post surgery there were improvements, specifically a decrease in pain and a decreased 19 reliance on external support. But her overall functional independence never improved. This case 20 is presented to raise awareness that improved BMI category post bariatric surgery is not 21 sufficient to guarantee that orthopedic risks have been minimized. Overall, weight loss does 22 improve both the metabolic profile and anesthesia risk, but the success rate of total hip 23 arthroplasties will be low if fat mass (i.e. high hip circumference) in the operative field remains 24 high. We are now repeatedly recognizing this problem but are not finding any case reports on 25 this issue. Therefore we provide a practical approach to evaluate these patients and describe 26 ways we have found to successfully address intra-operative challenges