Local Sources of Fallacy
If the pain and tenderness be located on the under-surface of the os calcis, there are several misconceptions possible.
(1) Careful examination may reveal a tendency to flatfoot, the pain being referable to strain on the posterior insertion of the plantar fascia.
(2) The root of the trouble may be a gonococcal inflammation of the plantar fascia, or of the periosteum covering the os calcis.
(3) A skiagram may show the existence of a bony spur on the inferior surface of the os calcis.
(4) The bursa under the os calcis may be inflamed.
(5) Also, as Tubby has pointed out, pain in the heel may be referable to shortening of one leg or constant standing, and more rarely to tuberculous disease of the os calcis.
If the pain and tenderness be located on the posterior surface of the os calcis, or in the tendo Achillis, the following should be excluded before assigning the trouble to “gout”:—
(1) Post-calcaneal Bursitis.—Inflammation of the bursa lying between the os calcis and the tendo Achillis is not uncommon. It may be uni- or bi-lateral, and in the majority of instances is attributable to violent exercise, or chafing of the heel by ill-fitting boots. The local swelling and tenderness at the site of the inflamed bursa and its aggravation by plantar flexion of the foot will afford a clue to its true nature. (An exostosis projecting from the hinder surface is sometimes a cause of post-calcaneal bursitis.)
(2) Synovitis of the Tendo Achillis.—Symptoms very similar to those above described have been met with in a teno-synovitis of the tendo Achillis, as evidenced by swelling of the sheath, tenderness, and silky crepitus.