Bilateral patellar tendon rupture on lupus undergoing corticosteroids: a case report

BACKGROUND: Patellar tendon rupture is a rare condition, especially when it is bilateral. The most frequent associated pathologies are systemic lupus erythematosus, chronic renal failure, or treatments like corticosteroids. The aim of this case report is to draw attention to the non-specific clinical aspect of this condition, to recall its radiological signs, and highlight the diagnostic contribution of musculoskeletal ultrasound. CASE PRESENTATION: A 39-year-old man was diagnosed with a systemic lupus erythematosus with cutaneous, pulmonary, cardiac, hematological, renal, and immunological manifestations. He was treated with high-dose corticosteroids. Within 3 months he presented with a total functional impotence of the knees. On physical examination, there was a gap in the right infrapatellar region, his patellae were abnormally ascended, and his left knee was swollen. Insall-Salvati ratio on knees conventional radiographies was 2.5 in the right and 2.25 in the left knee, assessing bilateral patella alta. Ultrasound revealed a complete and bilateral patellar tendon rupture. The treatment consisted in a surgical repair and physiotherapy. The patient was able to mobilize independently after 6 months. CONCLUSIONS: Bilateral patellar tendon rupture is exceptional. Systemic lupus erythematosus and corticosteroids are among trigger factors. Careful examination of the patellae should be done in front of knee extension deficit. Ultrasound plays a determining role in the diagnosis.