OCD & Osteochondoses of the Foot & Ankle

• Post-traumatic or idiopathic osteonecrosis

Anterolateral lesions: 

• may result from impaction of talus on fibula as the dorsiflexed ankle is forced into inversion
•  these lesions tend to be shallow

Posteromedial lesions: 

• may result from impaction of posteromedial talus on tibia, as plantarflexed ankle is forced into inversion & ER
• these lesions are deeper and cup shaped

: 

• palpate just posterior to the medial malleolus with the ankle dorsiflexed 

:

• osteochondral # may be anterior or posterior to dome, requiring plantar or dorsiflexion of ankle to be visible on mortise view
• if radiographs are negative consider repeat radiographs in 2-4 weeks

: (Berndt and Harty) 

Note: XR findings may or may not correlate w/ arthroscopic findings nor prognosis

I: small area of compression 

II: partially detached osteochondral lesion

III: completely detached, non-displaced fragment

IV: detached and displaced fragment

Bone Scan: - a negative bone scan will r/o the diagnosis

CT  or MR Scan: - offers more accurate staging of the lesion;

: (Hepple et al. Foot & Ankle International. 1999. 12:789-93)

1 - Articular damage only

2a - cartilage injury w/ underlying fracture + oedema

2b - cartilage injury w/ underlying fracture + No oedema

3 - detached & undisplaced

4 - detached & displaced

5 - subchondral cysts