Kellgren-Lawrence grade

What it means

Osteoarthritis is the gradual wear of the smooth cartilage that lines a joint, along with the bony changes that follow. The Kellgren-Lawrence grade is the classic five-point scale radiologists use to summarize how advanced that wear looks on a plain X-ray, mainly by measuring the gap between the bones and the bony spurs around them.

Why it appears on a CT or MRI report

The scale rises with severity. Grade 0 means no signs of osteoarthritis. Grade 1 is doubtful — a tiny spur or minimal change. Grade 2 is mild, with a definite small spur but the joint space still preserved. Grade 3 is moderate, with clear narrowing of the joint space and several spurs. Grade 4 is severe, with the joint space markedly narrowed or gone and hardened bone. Reports name the joint and the grade, and often the specific compartment of the knee involved.

What it usually means

A grade describes the structural picture, which is only loosely tied to how a joint feels. Many people with a grade 3 or 4 knee walk comfortably, while others with a grade 2 have significant pain. Because of this mismatch, treatment follows symptoms and function rather than the number alone. The mainstays across all grades are staying active, strengthening the muscles around the joint, weight management, and pain relief as needed. Higher grades with persistent, limiting pain are where a conversation about joint replacement eventually fits — but many people never reach that point.

When to follow up

Use the grade as background for a discussion about managing symptoms, not as a trigger for surgery. See a clinician if joint pain limits walking, sleep, or daily activity, or if the joint locks, gives way, or swells repeatedly. Sudden severe pain, a hot swollen joint, or inability to bear weight deserve prompt attention, as these can point to something other than ordinary wear.

A plain-language way to picture it

Think of the tread on a tire. Grade 0 is a fresh tire with deep tread; each grade wears the tread down further, until grade 4 is nearly bald with the rim showing through. A worn tire can still roll fine for a long time — the grade tells you how much tread is left, not whether the car is about to stop.