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Table 1 KL classification system for knee OA

From: Radiographic vs. MRI vs. arthroscopic assessment and grading of knee osteoarthritis - are we using appropriate imaging?

Grade

Radiograph findings

0

No findings of OA

1

Doubtful narrowing of joint space & possible osteophytic lipping

2

Definite osteophytes & possible narrowing of joint space

3

Moderate multiple osteophytes, definite narrowing of joint space, small pseudocystic areas with sclerotic walls & possible deformity of bone contour

4

Large osteophytes, marked narrowing of joint space, severe sclerosis & definite deformity of bone contour