Validating the forgotten joint score-12 in patients after ACL reconstruction

The forgotten joint score-12 (FJS-12), used to measure postoperative joint awareness, has been extensively validated to assess outcomes after arthroplasty, however the new score has never been validated in evaluating anterior cruciate ligament (ACL) reconstruction. The purpose of our study was to validate the FJS-12 versus the knee injury and osteoarthritis outcome score (KOOS) for patients who have undergone ACL reconstruction.

All patients who had undergone ACL reconstruction with the same arthroscopic surgical technique at our institution between 2011 and 2014 (medium-term follow-up group (M-FU)) or between 2000 and 2005 (long-term follow-up group (L-FU)) were considered for inclusion in the study. To analyze unidimensionality of the FJS-12, we calculated Cronbach's alpha, item-total correlations and conducted an exploratory principal component factor analysis. To assess convergent validity, we calculated Spearman correlation coefficients for the FJS-12 and its comparable scales.

We analyzed 58 patients of the M-FU (mean follow-up 31.5 (SD13.4) months, range 12-54), and 58 patients of the L-FU (mean follow-up 139 (SD15.2) months, range 120-179). The FJS-12 showed high internal consistency (Cronbach's alpha=0.95). Ceiling effects were considerably lower for the FJS-12 (M-FU 12.1%, L-FU 15.5%) compared with the KOOS subscales (M-FU 5.2-37.9%; L-FU 13.8-55.2%) and WOMAC subscales (M-FU 37.9-62.1%; L-FU 44.8-60.3%).

The FJS-12 is a valid measurement tool to evaluate outcomes of ACL reconstruction. This study extends the possibilities of measuring joint awareness as a patient-reported outcome parameter from joint arthroplasty to ACL reconstruction.