Postoperative Swelling Did Not Return to Preoperative Levels in Most Patients Two Years After Total Knee Arthroplasty

Swelling after a total knee arthroplasty (TKA) can result in pain, decreased range of motion, muscular inhibition, limitations in function, and negative perception of recovery. The objectives of this study were to determine how swelling changes after TKA and if swelling is associated with patient-reported outcomes, functional outcomes, or impairment measures.

This is a subanalysis of a two-arm, parallel, randomized controlled trial. Participants (n = 135) were recruited (mean age 64 years, 60% women, mean body mass index 28.7). The TKA participants were recruited and assessed pre-TKA and at 10 weeks, six months, and two years post-TKA. Demographic information was collected at the preoperative visit. Patient-reported outcomes (Western Ontario and McMaster Universities Arthritis Index (WOMAC) and patient satisfaction), functional outcomes (6-minute walk test [6MWT] and 30-second sit-to-stand test [30STS]), and impairment measures (quadriceps muscle strength, pain during functional measures, and knee range of motion) were collected at each clinic visit. Swelling was assessed using bioelectrical impedance analysis (BIA) and quantified post-TKA. Significance for all statistical tests was accepted at P < 0.05.

Mean swelling pre-TKA was 2.06 ± 7.8% and then was 15.3 ± 10.6% at 10 weeks, 9.6 ± 7.3% at six months, and 5.4 ± 7.1% at two years after TKA. After TKA, 5% of patients returned to pre-TKA swelling at 10 weeks, 12% of patients returned to pre-TKA swelling at six months, and 28% of patients returned to pre-TKA swelling at two years. In comparison to pre-TKA swelling, swelling at 10 weeks, six months, and two years post-TKA was significantly higher (all P < 0.0001). The BIA ratio was significantly correlated to function as measured pre-TKA by WOMAC (0.19, P = 0.03). The BIA ratio was significantly correlated to the 6-minute walk test (6MWT) at 10 weeks post-TKA (0.24, P = 0.007). The BIA ratio was not correlated to WOMAC, patient satisfaction, 6MWT, 30STS, quadriceps muscle strength, pain during functional measures, and knee range of motion at six months post-TKA or two years post-TKA (P = 0.10 to 0.95).

In most patients, postoperative swelling did not return to pre-TKA levels by two years after TKA. Furthermore, swelling remained elevated six months and two years post-TKA, and it is not associated with recovery of impairments and function.