Radiographic Changes in Patellar Height Following Rapid Weight Loss After Sleeve Gastrectomy: A Retrospective Observational Study.

Background/Objectives: Rapid weight loss following sleeve gastrectomy substantially reduces mechanical loading across the lower extremities, yet its effects on patellar height remain unknown. This study investigated early postoperative radiographic changes in patellar height following sleeve gastrectomy and evaluated whether these changes were associated with the magnitude of weight loss or body mass index (BMI) reduction. Methods: This retrospective observational study was conducted at a specialized high-volume bariatric surgery center in Kocaeli, Türkiye. Standardized bilateral knee radiographs were obtained preoperatively and at the routine fourth postoperative month in patients undergoing primary sleeve gastrectomy. Patellar height was assessed using the Insall-Salvati (IS), Blackburne-Peel (BP), and Caton-Deschamps (CD) indices. Results: A total of 155 consecutive patients were included. Body weight and BMI decreased significantly by the fourth postoperative month (both p < 0.001). The IS index remained unchanged (1.13 [IQR, 0.25] vs. 1.11 [IQR, 0.22]; p = 0.314), whereas the BP index decreased from 0.94 [IQR, 0.26] to 0.90 [IQR, 0.23] (p = 0.004), and the CD index decreased from 1.06 [IQR, 0.20] to 1.04 [IQR, 0.32] (p = 0.039). Although absolute postoperative BP values demonstrated weak associations with baseline and postoperative body weight and BMI, the magnitude of postoperative changes (Δ values) was not independently associated with the extent of weight loss or BMI reduction. In contrast, baseline patellar height independently predicted postoperative radiographic adaptation. Conclusions: Rapid postoperative weight loss following sleeve gastrectomy was associated with early radiographic changes in patellar height. Although these changes were statistically significant, they were modest in magnitude and appeared to be influenced predominantly by baseline patellar anatomy, which independently predicted postoperative radiographic adaptation, rather than by the extent of weight loss.