Subcutaneous pretibial cyst formation associated with anterior cruciate ligament allografts: a report of four cases and literature review.

Four clinical cases are described in which patients who had undergone anterior cruciate ligament reconstruction developed ganglion-like cysts at the external aparature of the tibial channel. All patients underwent operative treatment including curettage and bone grafting with the successful resolution of the cysts. A proposal, based on the incomplete incorporation of allograft tissues within bone tunnels, is given for the pathogenisis of these cysts, accompanied by a detailed description of the relevant literature.