Chen and Chmell Journal of Medical Case Reports 2011, 5:453 http://www.jmedicalcasereports.com/content/5/1/453 unable to actively perform a straight leg raise. On pal- pation, there was generalized tenderness and a high riding patella with a palpable gap beneath it consistent with a patellar tendon rupture. X-rays revealed marked patella alta with some mild HO in his distal quadriceps musculature (Figure 1). Our patient was consented for right patellar tendon repair and possible excision of the HO. During the operative repair, his patellar tendon was found to be avulsed off the inferior pole of his patella. A repair was accomplished by weaving sutures through the patellar tendon and drill holes in his patella. Post- operatively, our patient was placed in a long leg cast. Our patient was not given any therapy for HO prophylaxis. Postoperative follow-up visits for the first six weeks revealed no obvious complications with proper wound healing and no complaints from our patient. At six weeks postoperatively, his cast was removed. Physical therapy was instituted at that time. Follow-up visits for the next three months demon- strated a decreasing range of motion of his right knee. X-rays taken three months postoperatively revealed extensive HO within his quadriceps muscles as well as the patellar tendon (Figure 2). At four months post- operatively, our patient’s knee was completely fused at Figure 1 Anteroposterior X-ray of the patient’s right knee at the time of presentation. Some HO is seen superior to his knee. Page 2 of 4 Figure 2 Lateral X-ray three months after patellar tendon repair showing marked progression of HO. 45 degrees. Despite the deteriorating range of motion, plantar and dorsiflexion remained intact. Sensation was intact and there was brisk capillary refill. At this time our patient was given the option of leav- ing his knee locked at 45 degrees or performing a sec- ond surgery to fuse the knee in a more functional position. A total knee arthroplasty was not considered because our patient’s quadriceps mechanism had ossified thereby eliminating active knee extension. After several additional opinions, our patient and his mother decided to proceed with a knee fusion. A second surgical procedure was undertaken. Com- pression arthrodesis of the knee was accomplished with an intramedullary interlocking nail from the hip to ankle (Stryker T-2 Fusion Nail System) after the dis- tal femur and proximal tibia were transversely denuded