Kellgren–Lawrence classification
Commonly used radiographic grading system for osteoarthritis.
- Grade 0 — no radiographic OA
- Grade 1 — doubtful joint-space narrowing and possible osteophytes
- Grade 2 — definite osteophytes with possible joint-space narrowing
- Grade 3 — multiple osteophytes, definite joint-space narrowing, sclerosis and possible deformity
- Grade 4 — marked joint-space narrowing, large osteophytes, severe sclerosis and definite bony deformity
Outerbridge classification
Used for articular cartilage lesions.
- Grade 0 — normal cartilage
- Grade I — softening and swelling
- Grade II — fragmentation or fissuring affecting less than half the cartilage depth
- Grade III — fissuring extending deeper than half the cartilage depth but not through subchondral bone
- Grade IV — exposed subchondral bone
Ahlbäck concept
Historically used for knee osteoarthritis and based mainly on joint-space loss and bone attrition. Modern reporting often uses Kellgren–Lawrence or compartment-specific systems instead.
Clinical point
Radiographic grade should always be interpreted alongside symptoms, examination and functional limitation. Severe radiographic OA may be minimally symptomatic and vice versa.