What radiographic grading scale is used to categorize knee OA severity on plain films?

• A. Kellgren-Lawrence grade
• B. Ahlbäck grade
• C. Outerbridge grade
• D. Iwano grade

Answer: (A)

The Kellgren-Lawrence grading system is the standard way to classify knee osteoarthritis severity on plain radiographs. It assesses features you can see on X-ray, especially osteophyte formation and joint space narrowing, with additional changes like subchondral sclerosis and deformity appearing as the disease progresses. This framework provides a simple, widely used spectrum from no OA to severe OA, making it the go-to tool for describing radiographic knee OA and guiding prognosis and treatment planning.

Other scales exist, but they are used for different purposes or contexts. The Ahlbäck grade emphasizes medial joint space loss and bone attrition and is more historical and surgeon-focused. The Outerbridge classification applies to cartilage lesions seen during arthroscopy, not radiographs. The Iwano grade is another radiographic system, but Kellgren-Lawrence remains the most widely adopted for plain-film knee OA.