Chronological changes in lower leg swelling up to one year after total knee arthroplasty: A prospective case series

Lower leg swelling is a common complication following total knee arthroplasty (TKA). However, the long-term natural course of post-operative swelling remains unclear. This study aimed to evaluate chronological changes in calf circumference and to identify swelling patterns after TKA. Patients with osteoarthritis who underwent unilateral TKA between 2020 and 2021 were included. Calf circumference on the operated side was measured on the day of surgery, at discharge (2–3 weeks post-operatively), and at 1.5, 3, 6, and 12 months after surgery. The minimum detectable change (MDC) of calf circumference was calculated to define a detectable change in swelling. Chronological changes were analyzed using Friedman's test, and factors associated with increased calf circumference were evaluated using multiple linear regression. A total of 104 patients (mean age 76.2 years) were enrolled. The MDC was calculated as 1.59 ​cm. The median calf circumference increased significantly at 1.5 months post-operatively (31.0 ​cm) compared with the pre-operative value (30.0 ​cm), then gradually decreased to baseline level. A detectable increase in swelling was observed in 31% of patients at 1.5 months. A greater increase in calf circumference at 1.5 months was associated with lower pre-operative calf circumference (β ​= ​−0.35; p ​< ​0.001) and higher body mass index (β ​= ​0.14; p ​= ​0.02). Calf circumference increased significantly at 1.5 months after TKA, and one-third of patients showed a detectable increase in swelling. These findings help clarify the time course of lower leg swelling and may guide patient education and post-operative monitoring. • Calf circumference was measured at six time points up to 1 year after total knee arthroplasty (TKA). • Calf circumference was significantly increased at 1.5 months post-operatively. • One-third of patients showed swelling exceeding the minimum detectable change (MDC) at 1.5 months post-operatively. • High BMI and smaller pre-operative calf circumference were linked to swelling after TKA.