Low ceiling effect of Forgotten-Joint Score 12 after anterior cruciate ligament reconstruction: A longitudinal retrospective study

Abstract Background : Conventional patient-reported outcome measures (PROMs) are crucial for postoperative evaluation following anterior cruciate ligament reconstruction (ACLR); however, a disadvantage is their high ceiling effect. In contrast, Forgotten Joint Score-12 (FJS) is used for postoperative evaluation after total joint arthroplasty and has a low ceiling effect. We aimed to assess the ceiling effect in FJS, Knee Injury and Osteoarthritis Outcome Score (KOOS), and Lysholm Knee Score (LKS) at 1 and 2 years after ACLR and to predict the factors influencing FJS in the first postoperative year. Methods : This retrospective observational study included 47 patients who underwent double-bundle primary ACLR. We surveyed the demographic characteristics of the patients and the side-to-sided difference of tibial anterior translation and limb symmetry index of the single-leg hop test (SLH-LSI) at 1 year postoperatively. Additionally, we collected the FJS, KOOS, and LKS scores at 1 and 2 years postoperatively using identical predetermined questionnaires. We compared the FJS scores at 1 and 2 years postoperatively using paired t-tests and calculated the ceiling effects of the FJS, KOOS, and LKS scores. In addition, multiple linear regression analysis was performed to predict the factors influencing the FJS score 1 year postoperatively. Results : The participants included 32 women and 15 men (mean age, 27.2 years; mean body mass index, 22.8 kg/m 2 ). The mean FJS scores at 1 and 2 years postoperatively were 85.0 ± 18.1 and 89.8 ± 13.1, respectively, and had no significant differences (p = 0.06). The ceiling effects for the FJS, KOOS, and LKS scores at 1 year postoperatively were 23.4%, 34.0%, and 29.8%, and 36.2%, 43.8%, and 42.6% at 2 years postoperatively. The SLH-LSI score affected the FJS 1 year postoperatively (estimated coefficient 38.183, p < 0.05). Conclusions : The ceiling effect of FJS on ACLR up to 2 years tended to be lower than that of KOOS and LKS. Knee function related to the FJS was similar to that of other PROMs. The FJS may also be useful for assessing the short clinical course after ACLR.