What is this??

23 year old male presents with a painful foot following an inversion injury.  NAD on ankle examination.  Tender cuboid and base of 5th MT.  This is what the XR shows.  What do you think?

No fracture identified.  But have you noticed anything else?

There is a lucent lesion within the 2nd middle phalanx.  This is likely to be an enchondroma. 

Enchondromata are relatively common benign medullary cartilaginous neoplasm, usually found in children or young adults which can lead to pathological fractures or undergo malignant degeneration.


They are usually asymptomatic, but may be complicated by a pathological fracture or malignant transformation into a low grade chondrosarcoma. The latter is rare.
It is important to note that if an enchondroma is painful in the absence of a fracture, it should be considered malignant.

Enchondromas arise from rests of growth plate cartilage/chondrocytes that subsequently proliferate and slowly enlarge and are composed of mature hyaline cartilage. Hence, they are seen in any bone formed from cartilage.
Lesions are usually smaller than 3 cm, translucent, nodular, and are grossly grey-blue.
The typical distribution is:

• small tubular bones of the hands and feet: 50% 4
• large tubular bones, e.g. femur, tibia, humerus

The most important thing in the assessment is physical examination. It is important to know if the tumour is painful and the kind of pain it causes. There is greater concern if the pain occurs at rest or if the pain occurs at night and does not go away. Pain caused by activity is not as troublesome.  More information can be found here.