Validity and reliability of radiographic knee osteoarthritis measures by arthroplasty surgeons.
Most orthopedic surgeons do not routinely use radiographic classification systems to grade the extent of joint space narrowing in patients considered for total knee arthroplasty. The authors compared the validity and reliability of radiographic measures of tibiofemoral osteoarthritis by 2 experienced and 2 inexperienced orthopedic surgeons on individuals who subsequently underwent total knee arthroplasty. The Kellgren-Lawrence and the Osteoarthritis Research Society International classification systems were used by all surgeons to score the radiographs in 116 individuals in the Osteoarthritis Initiative, a federally funded cohort study of individuals with or at risk of knee osteoarthritis. Validity was judged based on comparison with the criterion centrally adjudicated consensus measures obtained by Osteoarthritis Initiative investigators. Weighted kappa, a chance corrected agreement index, was used to describe validity and reliability. Validity and intrarater reliability were substantial to almost perfect for 1 experienced and 1 inexperienced surgeon, with weighted kappas ranging from 0.76 to 0.96 for the surgical knees. The other experienced and inexperienced surgeons demonstrated moderate to substantial validity, with weighted kappas ranging from 0.43 to 0.70 and lower intrarater reliability. Interrater reliability was generally less than intrarater reliability. With minimal training, some surgeons can obtain valid and reliable measurements of knee osteoarthritis status in individuals who eventually undergo total knee arthroplasty. Measurement quality does not appear to be dependent on extent of surgeon experience. Some surgeons require additional training to become proficient in the radiographic classification systems, and future research should examine this issue.