Causes:
Trauma
Osteonecrosis
Site:
Anterolateral - dorsiflexion and forced inversion
Posteromedial - plantar flexion and forced inversion and external rotation. Deeper.
Radiograph:
Mortise view is needed
If negative repeat after 2-4 weeks
Berndt and Harty classification:
I: small area of compression
II: partially detached osteochondral lesion
III: completely detached, non-displaced fragment
IV: detached and displaced fragment
Bone Scan:
Usually done 8-12 weeks after diagnosis
A negative bone scan excludes diagnosis
If positive bone scan, CT or MRI needed;
CT Scan:
Accurate staging of the lesion
MRI:
References:
