Kellgren/Lawrence Grading in Cohort Studies: Methodological Update and Implications Illustrated Using Data From a...

The Cohort Hip and Cohort Knee (CHECK) is a cohort of middle-aged individuals with hip or knee pain. Radiographs were assigned Kellgren/Lawrence (K/L) scores under different conditions at each follow-up visit for 10 years. We aimed to describe and consolidate each scoring approach, then illustrate implications of their use by comparing baseline K/L scores assigned using 2 of these approaches, and evaluating their respective associations with joint replacement and incident radiographic osteoarthritis (ROA).

We compared baseline K/L scores assigned to hips and knees using 2 scoring approaches: 1) assigned by senior researchers to baseline images alone and 2) assigned by trained readers, with images read paired and in known sequence with up to 10 years of follow-up radiographs (Poisson regression). We evaluated the associations of baseline ROA (any: K/L grade ≥1; established: K/L ≥2) with joint replacement, and of K/L 1 joints with incident established ROA (survival analysis).

Of 1,002 participants (79% women, mean ± SD age 55.9 ± 5.2 years, body mass index 26.2 ± 4.0 kg/m² ), the second scoring approach had 2.4 times (95% confidence interval [95% CI] 1.8-3.1 for knees) and 2.9 times (95% CI 2.3-3.7 for hips) higher prevalence of established ROA than the first approach. Established hip ROA had a higher risk of joint replacement using the first approach (hazard ratio [HR] 24.2 [95% CI 15.0-39.8] versus second approach HR 7.7 [95% CI 4.9-12.1]), as did knees (HR 19.3 [95% CI 10.3-36.1] versus second approach HR 4.8 [95% CI 2.4-9.6]). The risk of incident ROA did not differ by approach.

This study demonstrates that evaluating ROA prevalence and predicting outcomes depends on the scoring approach.