When Does the Knee Feel Normal Again: A Cross-Sectional Study Assessing the Forgotten Joint Score in Patients After Total Knee Arthroplasty

The forgotten joint score (FJS) is a recent scoring system that assesses how natural the prosthesis feels after total joint arthroplasty. Although the FJS has been extensively applied in populations with total hip prosthetics, less is known about the patients undergoing total knee arthroplasty (TKA). The purpose of this study is to investigate the temporal relationship between TKA and the FJS. We evaluated 566 patients after TKA using the FJS questionnaire. Scores were calculated at the follow-up intervals of 1 (n = 79), 6 (n = 78), 12 (n = 81), 24 (n = 100), 36 (n = 76), 48 (n = 75), and 60 (n = 77) months. The scores ranged from 0-100, with a higher score indicating a more natural or “forgotten” joint. Postoperative FJS averages were 39.3 ± 27.4 at 1 month, 59.4 ± 28.3 at 6 months, 72.5 ± 24.2 at 1 year, 76.4 ± 23.4 at 2 years, 75.1 ± 24.2 at 3 years, 68.6 ± 28.7 at 4 years, and 64.4 ± 29.0 at 5 years. The average score at 1 month was significantly lower than the average scores at all other intervals. The average score at 6 months was significantly lower than the average scores at 12, 24, and 36 months. The average score at 60 months was significantly lower than the average score at 24 months. Based on the findings of this study, patients can expect marked improvement in the natural feel of the prosthesis during the first year after TKA, slight continued improvement at 2 and 3 years, and a decline after 4 years.