Characteristics

• Refers to pathology at the tendon–bone interface, where the Sharpey fibres interdigitate.

• May be divided into overuse syndromes and inflammatory causes.

• Often part of a generalized inflammatory condition, e.g. rheumatoid arthritis or psoriatic arthritis.

• Often due to widespread calcification of tendon origins and insertions into bone. Particularly important in the spine where thickening of the ligamenta flava can cause cauda equina syndrome.

• Severely affected tendons may ossify.

• Associated with inherited hypophosphataemia (vitamin-D-resistant rickets), adult hypophosphataemic osteomalacia, fibrous dysplasia and Fanconi's syndrome (aminoaciduria).

Clinical features

• Can be painful; may be an incidental diagnosis.

Radiological features

• Widespread calcification of tendon origins and insertions into bone.

• Erosions and bone proliferation (enthesophyte) may be seen.

Management

• Treat any underlying metabolic condition, then symptomatic relief.