Bilateral deep infrapatellar bursitis associated with tibial tuberosity enthesopathy in a case of juvenile ankylosing spondylitis.

A case of bilateral deep infrapatellar bursitis is reported in a 19-year-old man suffering from juvenile ankylosing spondylitis and surgically treated for bilateral tibial tuberosity enthesopathy. In addition to erosive non-specific bone remodelling the excised specimens showed, in the bursa, synovial layer hyperplasia with mild subintimal inflammatory cell infiltration, i.e. changes similar to those of synovitis in ankylosing spondylitis. The respective roles of the inflammatory "terrain" and of local shearing stress are discussed.