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Effects of a Broken Knee Cap after ACL Surgery

Many people who have torn their anterior cruciate ligament (ACL) have surgery to repair the injured ligament. Since the ligament has been torn, donor tissue is needed to replace it. The donor piece may come from tendon taken from the patient. Usually, this comes from the injured leg, but it can come from the other leg. The graft site may be the tendon that goes to the kneecap or it may come from a leg muscle.

After surgery of any kind, problems can occur. ACL repair has its share of possible complications. There may be infection or poor wound healing. The donor tissue may not be strong enough to hold the joint together. In rare cases, the kneecap may even break. This is called a patellar fracture.

Patellar fractures occur in about one percent of all cases when the patellar tendon is used as the donor tissue. The number of patellar fractures has decreased as more and more ACL repairs are done. There isn't a single cause of this fracture. In this study, eight people ended up with a patellar fracture either from blunt trauma or indirect injury. Three did not require additional surgery for the kneecap; five did.

Whatever the cause of patellar fractures, the final outcome when comparing other ACL patients isn't changed. There are no differences between patients with and without patellar fracture when the patellar tendon is used as the donor graft. Both groups typically end up with good bone healing, full knee range of motion, and a stable joint.

References: Drew A. Stein, MD, et al. The Incidence and Outcome of Patella Fractures After Anterior Cruciate Ligament Reconstruction. In Arthroscopy. July/August 2002. Vol. 18. No. 6. Pp. 578-583.

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