Heel fat pad involvement in rheumatoid arthritis and in spondyloarthropathies: an ultrasonographic study

Background: Heel fat pad inflammation and degeneration have been frequently proved to cause talalgia. Painful heel fat pad is often confused with plantar fasciitis, and only magnetic resonance imaging (MRI) or ultrasonography (US) can differentiate these conditions. Scanty data are available about heel fat pad involvement in the course of chronic polyarthritis. Objective: To investigate with US the heel fat pad involvement in patients with rheumatoid arthritis (RA) and spondyloarthropathies (SpA); to describe and compare the clinical and sonographic features of this lesion in the two groups. Methods: The heels of 181 consecutive outpatients with RA and 160 with SpA were studied by US and radiography. A control group of 60 healthy subjects was examined by US. Results: Two different patterns of involvement of the heel fat pad were observed. The inflammatory oedematous pattern was more frequent in patients with RA (6.6%) than in those with SpA (1.8%), and was associated with talalgia-even if it was not associated with plantar fasciitis or enthesophyte ( bony spur). The degenerative-atrophic pattern was less frequent (1.1% in RA, 1.9% in SpA), and was associated with plantar fasciitis and subcalcaneal enthesophyte. Conclusions: The inflammatory-oedematous lesion of the heel fat-pad is relatively frequent in RA and causes subcalcaneal pain. Degenerative-atrophic changes of the heel fat pad can be observed in RA and SpA, and seem to be associated with chronic abnormalities of the plantar fascia and of its enthesis.