Bilateral simultaneous infrapatellar tendon rupture: support for Davidsson's theory.

Rupture of the extensor mechanism of the knee is not an unusual occurrence. Bilateral simultaneous rupture, however, is rare. Most cases of bilateral simultaneous rupture occur in association with systemic disease, i.e., systemic lupus erythematosus, arteriosclerosis, diabetes, or secondary hyperparathyroidism. Only three cases without predisposing conditions have been reported. A case report of a 48-year-old black male without apparent risk factors who sustained spontaneous simultaneous rupture of the patella tendons is presented. Histologic evidence supports Davidsson's theory of multiple recurrent microtears within the tendon substance as a cause of rupture.