The normal ACL runs through the center of the knee and therefore during the surgery the graft is placed in the exact same position as your original ACL. To do this drill holes that are approximately one third of an inch in diameter are drilled into the femur and tibia at the attachment points of the normal ACL and the graft is then placed into the tunnels or drill holes. The graft is then secured with screws, metal staples or washers. The new tissue or graft should reapproximate the function of the normal ACL and restore stability to the injured knee. Although surgery cannot completely duplicate the anatomy of the normal uninjured knee, reviews of thousands of ACL surgeries throughout the United States shows that the surgery has a 90% or better success rate in satisfaction and in restoration of stability. In most large clinical trials', or published studies, 5% of the patients end up with a knee that is still not satisfactory or stable and may require further surgery.

Can the ACL be repaired or replaced with an artificial ligament?

A torn Anterior Cruciate Ligament, generally, cannot be repaired successfully. In the past, surgeons attempted to sew or repair the ACL, however these repairs tended to stretch out and the vast majority of these patients ended up with an unstable knee that required further reconstructive surgery.

Artificial ligaments once held promise, however, after a brief period of popularity in the 1980's the majority of these devices were withdrawn from the market having posted unacceptably high complication and failure rates.

Today, we replace the torn ligament with tissue obtained from elsewhere. The tissue, which is used to replace or reconstruct the ACL, is referred to as the graft.

What are the options for ACL graft material?

Hamstring and patellar tendons are most commonly used to replace the torn ACL. The tendons may be removed from the patients' knee or a donor (cadaver) graft may be used. Each physician has preferences that can be discussed on an individual basis:

Patellar Tendon: The central one third of the patellar tendon is removed along with a portion of bone from its attachment to the patella (knee cap) and proximal tibia (shin bone). The strength of the patellar tendon graft is the same or slightly greater than the original ACL. The surgery requires a two to three inch incision to obtain the patellar tendon graft. The remainder of the procedure is then performed with the assistance of the arthroscopy, through small incisions as discussed above.

Hamstring grafts: The use of hamstring tendons to replace the damaged ACL had been recently gaining popularity. Hamstrings tendons are generally significantly stronger than the original ACL, as well as being stronger than patellar tendon grafts. The graft can also be harvested through a one to two inch incision at the front of the knee.

Cadaver grafts: An alternative to using your own tendons as a graft is obtaining tissue from a donor bank. The donor grafts are generally felt to be quite safe, having been screened thoroughly for transmittable disease. The estimated risk of HIV or hepatitis transmission with current screening techniques is one in 1.5 million. In general, we prefer to reserve the use of donor tissue for those cases in which the individual has undergone prior reconstructive procedures about the knee as well as those unusual cases which require multiple ligament replacement or reconstruction.

What is a torn cartilage?

The other important structures within the knee are the menisci. "Menisci" is the plural form of the Latin word "meniscus". There are two menisci within the knee – the medial meniscus and the lateral meniscus. These structures are round rubber-like fibro cartilage spacers that act like washers or shock absorbers within the knee. When someone says that they have a "torn cartilage" they are describing a tear of a meniscus. Without a normal functioning meniscus people often develop early arthritis in the involved knee. Tears of the "cartilage", or meniscal tears, occur frequently in association with tears of the cruciate ligaments and often result in pain on the inner or outer aspect of the injured knee.

Is the surgery performed arthroscopically?

Arthroscopy, or arthroscopic surgery, is performed using small instruments that are inserted into the knee using 1/4 inch incisions. The arthroscope, which is the same diameter as a pencil, is connected to a television screen, or monitor, and allows the surgeon to examine the knee for internal damage such as cartilage and ligament injuries. Tears of the menisci may be addressed simply with the arthroscope; however, ACL reconstructions also require additional incisions to harvest the tendons and to drill the tunnels for the graft. The arthroscopy incisions are quite small (one quarter of an inch), while the incision for the ACL reconstruction is generally one to three inches in size.


Meniscal surgery: Some injuries such as tears of the menisci can be treated using the arthroscope. The goal of arthroscopic meniscal surgery is to preserve as much of the normal meniscus as possible as the menisci protect the knee from early arthritis.

The outer one third of the meniscus has a good blood supply and therefore tears at this level have the potential to heal if sewn or repaired. The success rate with meniscal repairs is quite good. At five years after surgery 80 percent of the repairs are sound and asymptomatic in individuals with a stable knee. Unfortunately individuals with a loose or lax knee will most likely rehear the meniscus as the knee continues to give out. It is for this reason that we will often recommend that the ACL be reconstructed in individuals who present with cartilage and ligament damage. Meniscal repairs may be performed arthroscopically with absorbable tacks, darts or screws. Larger tears, however, may require sutures. For a suture repair an additional incision is made at the back of the knee and needles are passed through the knee and out the back where the sutures are then tied. Although we cannot guarantee that a repaired meniscus will heal it is best to make every attempt to preserve as much of the meniscus as possible. More often, however, the tears occur on the inner portion of the meniscus, which does not have a blood supply and, therefore, cannot heal. These tears must be trimmed or smoothed, removing the damaged, torn or chewed-up portions of the meniscus.

In extremely rare cases one might even consider replacing badly damaged menisci with cadaver, or donor, menisci. As this type of surgery requires special planning and is still in the experimental phase it is generally performed as a salvage procedure at a later date.

Articular cartilage surgery: The ends of the bones which come together to form the knee are covered with a glistening, slippery white material referred to as articular cartilage. Occasionally, this articular cartilage may be damaged with trauma. In such cases your surgeon may elect to smooth the damaged area in hopes that scar will fill in at the defect . In larger defects he may schedule future surgery to transfer plugs of articular cartilage to the damage area or he may take a sample of your cartilage to be grown in a laboratory for a future surgery to resurface the damaged area. At this time, however, most insurance companies refuse to authorize such procedures. Unfortunately, there is often not much that can be done to repair damaged articular cartilage that has simply worn out from age or repeated trauma.

When should the surgery be performed?

In only the most severely injured knee is surgery indicated on an urgent or immediate basis. Generally, we prefer to let some of the initial pain and swelling subsides. Once patients have relatively pain free motion we can proceed with reconstruction of the torn ACL - in those individuals who are candidates for surgery. This approach not only allows for any healing that might occur to take place, but also decreases the risk of excessive scar formation in those patients who subsequently require or desire surgery.

What are the risks of surgery?

Occasional minor aching as well as stiffness is not uncommon and a certain amount of permanent numbness around the incisions at the front of the knee is to be expected. Additionally, as with any surgery there are risks which include (but are not limited to) the following: infection, blood clots, stiffness, pain, residual laxity or graft failure, anesthetic reactions and other rare or unexpected complications. There is also a possibility that further surgery may be necessary to remove scar or hardware (i.e., screws).

The patient therefore should understand the risks, benefits and alternatives to surgery before deciding whether he or she would rather operate on his or her lifestyle and avoid sports or proceed with the surgical approach.

What happens after surgery?

At the time of the surgery a sterile dressing is applied, as well as a special cooling pad that circulates ice cold water around the knee to diminish pain and swelling after the surgery. Crutches are recommended often for four to six weeks, depending upon the exact injury to your knee as well as your doctors' preferences.

Most of the ACL reconstruction's performed in the United States are performed on an outpatient basis with the patient going home on the same day as the surgery. Remaining overnight may be an option if the surgery is performed at a hospital instead of an outpatient surgical facility.

The amount of weight that you will be allowed to place on the side that has had surgery, as well as when you will resume physical activity, will be determined also by your doctor based upon the type of graft, graft fixation and what type of meniscal or articular cartilage injuries were encountered and treated during the surgery.

Regaining normal strength, range of motion and function takes a great deal of time and requires a serious and determined effort on the part of the patient. It is best to see a physical therapist before the surgery to review exercises to be done after surgery as well as to instruct you in the proper use of crutches. Physical therapy is also prescribed after the surgery to help you regain motion, strength and function.

High level athletes are often able to resume sports at six months from the time of surgery, if they have 90% of their normal strength back, while the recreational athlete who does not aggressively rehabilitate his or her knee may take longer. Once the graft has healed, statistically, it is more common for a patient to tear the ACL on their normal knee than on the reconstructed knee.

Will I need a brace after surgery?

There are actually two types of braces that may be utilized. One is a larger well padded brace applied in the operating room after the surgery. This 'post-operative' brace is intended to protect the knee during the early stages of healing and is not always recommended. The use of a post operative brace varies from surgeon to surgeon.

Another type of brace is the custom ACL or Sports Brace. These rigid braces are commonly prescribed for patients after ACL reconstructive surgery to protect the graft from injury as the patient resumes sporting activities. The use of such a brace after an ACL reconstruction remains controversial and most patients eventually return to all sports without a brace. Most surgeons, however, still recommend continued use of a brace, even after a successful ACL reconstruction, by the linemen in football and skiers, both of whom remain at greater risk for ACL injury.