Primary aneurysmal bone cyst of patella

Of all the aneurysmal bone cysts (ABC) occurring in the body, less than 1% are seen in the patella. We report here, a 27-year-old woman with Stage III ABC of patella. Curettage, chemical and thermal cautery of the bed followed by autogenous bone grafting of the defect was done. At two-year follow up, there was a suspicion of lucency in the middle of the patella. However a repeat curettage revealed only fibrous tissue. Now at four years of follow up, the bone graft remained well incorporated. Patient has mild anterior knee pain on stair climbing but regained normal knee function.