Impact of Obesity on Daily Activity Following Total Knee Arthroplasty.

BACKGROUND: Obesity is a major risk factor for knee osteoarthritis, frequently requiring total knee arthroplasty (TKA). Although TKA improves mobility and reduces pain, obesity's influence on postoperative activity and gait metrics remains unclear. This study investigated the impact of body mass index (BMI) on daily activity following TKA. METHODS: A prospective cohort study included 152 patients undergoing unilateral TKA, stratified into normal-weight (BMI: 18.5 to 25), overweight (BMI: 25.0 to 30), obese (30.0 to 40), and morbidly obese (BMI > 40) groups. Objective metrics-step count, standing hours, gait speed, steadiness, and 6-min walk test (6MWT)-were recorded preoperatively and at six weeks, six months, and 12 months postoperatively using watches. Multivariable regression analyses controlled for age and sex. RESULTS: Morbidly obese patients had significantly lower preoperative step counts (2,104 ± 1,622 versus 4,893 ± 2,977; P = 0.017). Postoperatively, all groups showed improvements in step count, gait speed, and steadiness, but morbidly obese patients maintained lower activity metrics. At 12 months, morbidly obese patients' step counts (2,255 ± 1,639) were significantly lower than normal-weight patients (7,262 ± 3,141; P = 0.011). Improvements in step count, gait speed, standing hours, and patient-reported outcomes (Knee Injury and Osteoarthritis Outcome Score, Joint Replacement [KOOS, JR], and EuroQol Five-Dimensional Questionnaire [EQ-5D]) occurred across BMI groups, without significant intergroup differences. Regression analyses identified higher BMI as associated with reduced postoperative activity at 12 months (P < 0.05), although the small size of the morbidly obese subgroup limits the strength of conclusions for this category. CONCLUSIONS: Higher BMI was associated with lower postoperative daily activity following TKA. Despite lower absolute activity levels in higher BMI groups, the magnitude of improvement from baseline was similar across all BMI categories. Prehabilitation and tailored rehabilitation programs targeting obese individuals' specific needs may optimize recovery and enhance postoperative physical activity.

Duke Scholars

Author Samuel S. Wellman Orthopaedic Surgery

Author Thorsten Markus Seyler Orthopaedic Surgery

Author Michael Paul Bolognesi Orthopaedic Surgery

Author Sean Ryan Orthopaedic Surgery