Different descriptions of the classification criteria of Kellgren and Lawrence used in various epidemiological studies
| Definition grades | Original | Alternative 1 | Alternative 2 | Alternative 3 | Alternative 4 |
|---|---|---|---|---|---|
| Grade 0: No osteoarthritis | No osteoarthritis | No osteoarthritis | No osteoarthritis | No osteoarthritis | No osteoarthritis |
| Grade 1: Doubtful | Doubtful narrowing of joint space and possible osteophytic lipping | Possible osteophytes | Minute osteophyte, doubtful significance | Possible osteophytes only | Possible osteophytic lipping |
| Grade 2: Mild | Definite osteophytes and possible narrowing of joint space | Definite osteophytes | Definite osteophytes, unimpaired joint space | Definite osteophytes and possible JSN | Definite osteophytes and possible JSN |
| Grade 3: Moderate | Multiple osteophytes, definite narrowing of joint space and some sclerosis and possible deformity of bone ends | Osteophytes and JSN | Moderate diminution of joint space (with osteophyte) | Moderate osteophytes and/or definite narrowing | Moderate multiple osteophytes, definite JSN, some sclerosis and possible bone contour deformity (bony attrition) |
| Grade 4: Severe | Large osteophyte, marked narrowing of joint space, severe sclerosis and definite deformity of bone ends | Large osteophytes, marked narrowing of joint space and definite deformity | Joint space greatly impaired with sclerosis of subchondral bone | Large osteophytes, severe JSN and/or bony sclerosis | Large osteophytes, marked JSN, severe sclerosis and definite bony contour deformity (bony attrition) |
JSN, joint space narrowing.