MRI Changes of Lecouvet et al for Early Spontaneous Osteonecrosis of the Knee (SONK)

 

Patient selection: spontaneous onset of medial (or lateral) knee pain

 

Exclusion: The presence of evidence for osteonecrosis on plain X-ray (epiphyseal collapse, subchondral bone fracture, etc.).

 

Marrow edema will be present as a diffuse area of increased signal intensity on T2-weighted images of the affected condyle. This is a reversible change.

 

Parameters:

(1) subchondral areas of low signal intensity in the condyle on T2-weighted images

(2) epiphyseal contour deformity in the affected condyle

(3) lines of low signal intensity in the affected condyle

Epiphyseal Contour Deformity	Grade
absent	0
possible flattening	1
flattening with possible depression	2
depression	3

 

 

Parameter	Finding	Points
subchondral areas of low signal intensity	absent	0
	present	1
epiphyseal contour deformity	absent	0
	present (Grade 2 or 3)	1
lines of low signal intensity	absent	0
	superficial	0
	deep	1

 

where:

• There are different ways of using the different grades of epiphyseal contour deformity. The presence of a definite depression (Grade 3) is evidence for SONK. However, grades 1 and 2 may be more suggestive evidence.

• The absence of subchondral areas of low signal intensity is indicative of complete reversibility (page 76).

• The absence of any epiphyseal contour deformity was indicative of complete reversibility (page 76).

 

number of findings indicative of irreversible osteonecrosis =

= SUM(points for all 3 parameters)

 

Interpretation:

• minimum number of findings: 0

• maximum number of findings: 3

• If none of these findings are present then the patient has reversible disease.

• The presence of all 3 findings correlates with irreversible disease.