Comparison of BLOKS and WORMS scoring systems part I. Cross sectional comparison of methods to assess cartilage morphology, meniscal damage and bone marrow lesions on knee MRI: data from the osteoarthritis initiative.

OBJECTIVE

To compare two semiquantitative scoring systems for assessing the prevalence and severity of morphologic cartilage lesions, meniscal damage and bone marrow lesions (BMLs) from Magnetic Resonance Imagings (MRIs) of knees with osteoarthritis (OA).

METHODS

From participants in the OA Initiative (OAI), a sample of 115 knees with radiographic OA at high risk of cartilage loss, were selected based on risk factors for progression. Knee MRIs were read separately using both Whole Organ MR Scoring (WORMS) and Boston-Leeds OA Knee Scoring (BLOKS), and a subset was fed back to readers for reliability. Baseline readings were used for comparison of the two methods for inter-reader reliability as well as agreement on presence/absence and severity of MRI features at both the compartment level and finer anatomical subregion levels.

RESULTS

Both methods had high inter-reader agreement for all features studied (kappa for WORMS 0.69-1.0 and for BLOKS 0.65-1.0). Although the methods agreed well on presence and severity of morphological cartilage lesions (inter-method kappas from 0.66 to 0.95), BLOKS was more sensitive for full thickness defects. The two methods gave equivalent results for extent (kappa 0.74-0.80) and number (Spearman's Rho=0.85) of BMLs, and little extra information was obtained using the more complex BLOKS BML scoring. Similar results were also obtained for the common types of meniscal damage and extrusion (inter-method kappa 0.85-0.94), but the inclusion in BLOKS of meniscal signal abnormality and uncommon types of tear may be an advantage if these prove clinically meaningful.

CONCLUSION

Both WORMS and BLOKS had high reliability. The two methods gave similar results in this sample for prevalence and severity of cartilage loss, BMLs and meniscal damage. Selecting between, or combining, the two methods should be based on factors such as reader effort, appropriateness for the goals of a study, and longitudinal performance.