Asymmetric joint space narrowing with osteophytes, subchondral sclerosis and cysts, reported by compartment and graded (Kellgren–Lawrence) on a weight-bearing view — the grade and the compartment decide injection, osteotomy or arthroplasty.
Orient first
- Weight-bearing views are required at the knee; supine views underestimate narrowing.
- Symmetric narrowing with erosions and periarticular osteopenia points to inflammatory arthritis instead.
- Kellgren–Lawrence 0–4: doubtful narrowing and possible osteophyte (1) to marked narrowing, large osteophytes and deformity (4).
Acquire the study
- Knee: standing AP (or PA flexed/Rosenberg), lateral and skyline patellofemoral views; hip: AP pelvis and lateral hip; hands: PA of both hands.
The manoeuvre
- Each compartment separately: medial tibiofemoral, lateral tibiofemoral, patellofemoral — joint space width in mm.
- Osteophytes at the margins; subchondral sclerosis and cysts.
- Alignment: varus or valgus on the standing view.
- Hands: distal and proximal interphalangeal joints (Heberden, Bouchard nodes), first carpometacarpal joint; central erosions (erosive OA).
- Kellgren–Lawrence grade per joint; compare with the prior study.
What confirms it
- Asymmetric narrowing with osteophytes in the typical distribution on a weight-bearing radiograph.
What licenses you to exclude it
- Preserved joint space without osteophytes excludes radiographic OA; it does not exclude cartilage or meniscal damage.
The classic misread
- Grading from a non-weight-bearing view.
- Missing chondrocalcinosis or an erosive pattern that changes the diagnosis.