Risks of ACL Surgery and Ligament Reconstruction

ACL tears are a common knee injury that often requires patients to have surgery to reconstruct the torn ligament. Some patients struggle with the decision to have ACL reconstruction surgery because there are possible risks of surgery. Learn about some of the common complications of ACL surgery and how you can ensure the best possible outcome.

A man with a large scar on his knee
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Anterior Knee Pain

The most common complication of ACL surgery is pain around the kneecap. This complication is highest in patients who have surgery performed with a patellar tendon graft, as these patients have bone removed from the kneecap as part of that surgical procedure. These patients can even have complications including patellar fracture and patellar tendon tear, although these are very uncommon. However, all patients, even those having hamstring grafts or donor grafts, can also have symptoms of anterior knee pain.

Typical anterior knee pain is thought to be a result of altered mechanics of the joint, and can often be overcome with extensive physical therapy. Adherence to post-operative rehab protocols is important for athletes to ensure their knee mechanics improve.

Infection After ACL Surgery

Infection is a rare complication but can be serious when it occurs. When the infection is inside the knee joint, there is concern about the ACL graft becoming infected. Your body cannot effectively fight infection on the graft, and sometimes the graft needs to be removed in order to cure the infection.

Taking steps to avoid infection include following your surgeon's specific instructions both before and after surgery. Many surgeons recommend cleaning the knee with antibacterial soap prior to surgery, and then it is important to follow any specific bandage instructions after surgery. If you do have signs of infection including fever, chills, increasing knee swelling or pain, let your surgeon know as soon as possible.

Re-Rupture of the ACL Graft

Repeat rupture of the ACL graft is also uncommon but does occur. Whenever there is a re-rupture of the graft, your surgeon should carefully assess for possible technical failures of the first surgery. Possible problems that can lead to re-tear of the ACL include suboptimal positioning of the graft, improper tension on the graft, or failure of the fixation of the graft.

ACL grafts are very strong. In fact, autograft tissue (tissue from the patellar tendon or hamstring tendon) is stronger than your own ACL. Failure of these grafts is often a result of one of these problems. Allograft tissue (donor tissue), on the other hand, is not as strong, and re-tear rates are known to be higher with this type of graft. That is why higher demand athletes often select their own tissue, even though rehab may be more difficult.

Stiffness (Arthrofibrosis)

Stiffness after ACL surgery is frequently encountered. Fortunately, most patients with stiffness can address this complication with aggressive rehabilitation. While most cases of stiffness can be addressed with rehab, one exception is called a cyclops lesion. A cyclops lesion occurs when a ball of scar tissue forms in the front of the knee, causing an inability to fully straighten the knee after ACL surgery. An arthroscopic surgery to clean out this scar tissue is often necessary for patients with a cyclops lesion.

The most critical step to avoid stiffness is to get the knee moving quickly after ACL surgery. In the past, doctors used specialized machines to bend the knee, called CPM machines, although these have not been shown to lead to long-term improvement. Many surgeons are becoming more aggressive with early rehab, and avoiding braces after surgery, in order to get the knee moving quickly.

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