Table 1 Features that are scored* on the Boston–Leeds Osteoarthritis Knee Score (BLOKS)
BLOKS featureReliability (weighted kappa (95% CI))
Bone marrow lesion (BML) sizeScore of 0–3 applied for BML volume in nine different regions
BML percentage areaScore of 0–3 applied for percentage surface area adjacent to subchondral plate
Percentage of lesion BML rather than cystScore of 0–3 for percentage of lesion that is bone marrow lesion as distinct from cyst
Cartilage 1Score of 0–3 for size of loss and percentage of loss in region that is full thickness
Cartilage 2Extent of any cartilage loss at specified points
OsteophyteScore of 0–3 applied for osteophyte size in12 locations
SynovitisScore of 0–3 applied for synovial volume
EffusionScore of 0–3 applied for size of effusion
Meniscal extrusionScore of 0–3 applied for amount of extrusion in four locations
Meniscal signalScored as present or absent in six regions.
Meniscus tearType of tear or degenerative process scored as present or absent in six regions.
LigamentsPresence/absence of tear
Periarticular featuresPresence/absence
  • *A more complete description is included in the Appendix online at