Spontaneous disruption of the knee extensor mechanism is associated with systemic diseases, steroid usage, and repeated microtrauma. Early repair or reconstruction is imperative for optimal outcome. We report 2 cases of spontaneous disruption of the bilateral knee extensor mechanism. The first patient had connective tissue disease and long-term steroid use. She had acute-on-chronic spontaneous bilateral patellar tendon rupture. She underwent reconstruction with an allograft and defunctioning wire. The second patient had end-stage renal failure with tertiary hyperparathyroidism and was on haemodialysis. He had a right patellar tendon rupture and a left quadriceps tendon rupture. He underwent primary repair of both tendons. Postoperatively, both patients followed a strict physiotherapy regimen and achieved good functional outcome.