Evaluations for knee osteoarthritis (OA) or post-operative total knee arthroplasty (TKA) have mainly been assessed by objective scales. Though the Knee injury and Osteoarthritis Outcome Score (KOOS) is attracting attention as a patient-based outcome score, the relationship with conventional objective scales after TKA remains controversial. The purpose of this study was to investigate the relationship between KOOS and conventional objective scales and evaluate the features of patient-based outcome scores.
Subjects were 130 post-operative patients involving 186 knees treated with TKA. Their mean age was 74.0 ± 8.0 years, and the follow-up period was 43 months. Japanese Orthopaedic Association (JOA) score, original Knee Society Score (KSS) and surgeon's satisfaction score were scored as conventional objective scales besides KOOS. Spearman's correlation coefficient was estimated between these scales. Comparisons between OA and rheumatoid arthritis (RA) as well as primary and revision surgery were performed by the Mann-Whitney U test.
There were strong correlations between KOOS activities of daily living (ADL) and JOA score (r = 0.806), KSS function score (r = 0.803) and between KOOS pain and KSS knee score (r = 0.689). However, there was a poor correlation between KOOS and surgeon's satisfaction score (r = 0.188-0.321). TKA for RA showed poorer results only in KOOS pain (p = 0.003), and revision surgery showed poorer results in KSS function, KOOS symptoms and KOOS quality of life (QOL).
This study suggested that conventional objective scales reflected mainly ADL disturbances in post-operative TKA patients. Furthermore, patient-based outcome scores made it possible to evaluate and detect a minute change of knee pain and QOL in TKA patients. The Japanese KOOS was a useful tool to evaluate conditions after TKA.