Application of Differential Equations for Pain Progression according to BMI Post TKR Surgery

Abstract

Total knee replacement (TKR) is a widely adopted surgical intervention for alleviating severe pain and improving mobility in patients with advanced knee osteoarthritis. A growing body of research has investigated the role of body mass index (BMI) in influencing postoperative outcomes, particularly pain relief and functional recovery. Evidence from multiple cohort studies and prospective trials demonstrates that although obese and morbidly obese patients often present with worse preoperative pain and functional limitations, they experience substantial improvements following TKR. In many cases, higher BMI groups report equal, and sometimes greater, relative gains in pain reduction and functional capacity compared to normal-weight patients, suggesting that obesity should not be viewed as a limiting factor in the effectiveness of TKR. At the same time, variations exist in recovery trajectories across BMI categories, with overweight patients frequently showing slower pain resolution, while obese and underweight groups may recover more rapidly than expected in the first 24 hours or early months post-surgery. Studies have also highlighted the influence of additional variables such as gender and leg alignment in shaping postoperative pain experiences. Overall, the literature indicates that BMI alone is not a determinant of long-term outcomes, and TKR provides significant clinical benefits across all weight categories. These findings underscore the importance of inclusive surgical recommendations and emphasize the need for personalized pain management strategies that address the nuanced recovery patterns associated with different BMI groups.