Posterior interosseous nerve compression due to an enlarged bicipital bursa confirmed by MRI.

Posterior interosseous nerve compression is a well-described clinical entity with many aetiologies. Fewer than 12 documented cases of the condition due to an enlarged bicipital bursa exist in the literature. We describe a case in which magnetic resonance imaging (MRI) was used in the preoperative assessment of a mass in the proximal forearm with a clinical diagnosis of partial posterior interosseous nerve compression.