ACL Tears

Surgery For ACL Tears

Not all ACL tears need surgery. The decision as to whether to have surgery will depend on how active the person is, and how unstable the knee.

Treatment decisions for ACL tears are always individualized – tailored to each individual. The decision whether to offer surgery is based on the person’s age, activity level, how unstable the knee is, and whether other structures in the knee have been injured.

It is important to keep in mind that surgery to reconstruct a torn ACL is not an emergency for most people. Many people with a torn ACL do not need surgery at all. Even though the chances for complete success from surgery are now excellent, surgery is not for everyone. This is because not everyone needs the ligament repaired to return to his or her pre-injury level of function. It is important to distinguish whether the work, recreational, and athletic activities of the person is light, moderate, or strenuous. Another important issue that needs to be understood by the individual considering ACL reconstruction is that it requires many weeks and months of hard work in rehabilitation following the reconstruction. This needs commitment and time.

The Ultimate Deciding Factors…

  • Whether the injury is a recent tear or an old ACL problem, individuals need to consider their present activity level and decide if their daily activities and livelihood would be affected by the injury. The question of whether to have surgery to reconstruct the torn ACL arises most frequently with less athletically inclined older persons. Generally in such people, if the instability is severe, and the knee is constantly buckling, the decision to offer surgery is intended to prevent further damage to the knee and stop the daily discomfort of the knee giving way.
  • On the other hand, if the knee instability can be controlled by avoiding activities that the individual doesn’t really mind avoiding, then going the “conservative” route and avoiding surgery is often a very good choice – and many people are satisfied with it. Certainly, there are many older athletes who are willing to avoid basketball, soccer, or racquetball, and stick to jogging or biking for fitness. As long as their knees are stable and pain-free for these activities, they are happy. Also with the use of a functional brace, many of these people find they can do most of what they wish to do without significant problems.
  • For those people who choose not to have surgery, this does not mean going without any treatment at all. There is still a treatment program to be followed emphasizing strengthening the leg muscles and learning to better control the knee and to avoid those situations most likely to cause instability. Many people benefit from this kind of rehabilitation.
  • If athletics is a regular part of your life, or if your work is likely to be affected by mild instability of the knee (for example, construction workers or other non-sedentary type jobs), your physician will lean toward reconstructing the torn ligament.
  • In general, stronger and fitter is better – and this applies to operated and non-operated knees equally.

If You Are Going To Have Surgery:

If you are going to have surgery it is important to be both mentally and physically prepared. This includes understanding the injury, the surgery, and the rehabilitation goals.

For most individuals with a torn ACL, reconstruction will restore stability to the knee. Reconstructed knees are reliable and stable. The knee will not give out unexpectedly and will allow the person to return to previous work and athletic activities, usually without any compromises (though it is commonly recommended that a protective brace is worn for athletic activities).

Approximately 90% of individuals return to their previous level of activity without restrictions. For the competitive athlete, this can be extremely important. In some cases, it is even a matter of earning a living or funding a college education. In the case of non-athletes, it can be equally as important in returning to their pre-injury level on and off the job.

Preparing for Surgery

How is the ACL repaired?

Preparing For Surgery

The initial goals before surgery are to:

  • Reduce swelling in the knee.
  • Try get back the normal range of motion of the knee.

Depending on your age, certain preoperative tests will be arranged, such as blood tests, urine tests, chest x-ray, and an ECG (heart monitoring).

Leg measurements may be taken to order a knee brace. Your rehabilitation program will be discussed in detail with you.

You will meet the anesthesiologist, who may offer you a choice of anesthesia:

  • If you choose a general anesthetic, you will be asleep during the procedure.
  • If you choose an spinal, an injection is given into the back that numbs the lower half of the body. This wears off a couple of hours after surgery.

If you have an spinal anesthetic, you can often watch the whole operation on the television monitor.

Need to Know:

  • If you take aspirin, anti-inflammatory drugs, or blood thinners, you should stop taking them one week before surgery to minimize bleeding. Discuss this with your doctor.
  • You should not eat or drink anything (even water) for six hours before surgery. This usually means not eating or drinking anything after midnight the night before surgery.
  • If you would normally be taking medication during the hours before surgery, talk to your doctor.

Need to Know:

What to tell your doctor:

Be sure to tell your doctor:

  • If you are allergic to iodine or any other drugs
  • What medications you take
  • About your past medical history
  • If you’ve ever had deep vein thrombosis or other blood clotting abnormalities

Also tell your doctor if you develop any of these symptoms prior to surgery:

  • Fever or chills
  • Irritation of the eyes, ears, throat or gums
  • Sniffling or sore throat
  • Boils or inflamed skin abrasions and cuts

How Is The ACL Repaired?

There are a number of different techniques available to repair a torn ACL. Each surgeon has his preference for each particular situation.

In fact we don’t talk about ACL “repair” but rather about ACL “reconstruction.” This is because a torn ACL cannot simply be repaired by sewing it together again. This was the method tried in the early days of repairing ACL tears, but it was shown to be ineffective. Thus, newer methods were developed which involve reconstructing the ACL ligament, including substituting a new ligament for the damaged one. Using tendons from other parts of the body as a substitute for the ACL was found to be the most effective way of reconstructing the torn ACL. Currently, the two most popular methods in use are using part of the patella tendon or using a hamstring muscle tendon.

Today ACL reconstruction is essentially an arthroscopic procedure, though some surgeons throughout the world still prefer to open the knee.

An arthroscope is a pen-shaped instrument to which a tiny video camera is attached. It contains optical fibers, a light source, and lenses that can magnify images 25 to 30 times. The camera attached to the end of the arthroscope sends images to a video screen. The surgeon looks at the screen and is able to get an exceptionally clear view of the inside of the joint. Because the procedure can be done using an arthroscope, and using small specialized instruments without big incisions and excessive trauma to the tissues, it is really well suited to be an outpatient procedure (one that does not require an overnight stay at the hospital). Many ACL reconstructions are commonly performed as outpatient procedures. However, many doctors prefer to keep patients overnight in the hospital following surgery.

Before actually reconstructing the torn ligament, the surgeon uses the arthroscope to carefully survey the whole joint, looking at and evaluating each key structure. During this portion of the procedure, any additional damage to any of the other knee structures can be identified, and where appropriate, is corrected surgically.

There are a number of choices available to the orthopedic surgeon in determining how best to reconstruct the torn ACL. They all involve a “graft” using something to substitute for the torn ACL.

Each of the available ACL graft tissue choices requires a unique harvesting technique. Furthermore, there are usually different methods used for fixing the grafts in the bone tunnels, depending on the characteristics and properties of the tissue selected. Because of these differences in graft techniques, the type of surgery chosen is frequently made by the surgeon based on his or her experience and comfort level with the chosen technique.

Typically, an ACL reconstruction takes two to two and a half hours. The anesthesia may be general anesthesia or a spinal anesthesia. General anesthesia allows the individual to be asleep through the entire procedure. Spinal anesthesia involves an injection in the back that numbs only the lower body. A medication is also administered with a spinal anesthesia to keep the individual sedated throughout the procedure.

There are several available operative procedures:

1. Patellar tendon graft procedure

Since it was popularized in the mid-1980s, the patellar tendon graft was the the “gold standard” choice for ACL reconstruction. This type of ACL replacement uses the middle third of the person’s own patella tendon and is referred to as a bone-tendon-bone (BTB) graft. However, most surgeons have abandoned this technique in favor of the hamstring graft (see below)

In this particular technique,

  • Two tiny incisions for arthroscopic instruments are usually placed on either side of the patellar tendon.
  • A one- to two-inch incision is made over the patellar tendon on the front of the knee and the tendon is exposed. The middle one-third of the patellar tendon is carefully removed, together with two bits of bone on either end (hence it is called a ‘bone-tendon-bone graft’).
  • Two small tunnels are then drilled into the bones on either side of the joint, in the area where the torn ACL normally attaches to the bone, to allow for fixation of the new ligament.
  • The patellar tendon graft is then passed into the joint, placed in a position similar to the original ACL, with the bone pieces at each the end of the graft fitting nicely into the tunnels that have been drilled in the bone.
  • The new ACL is then secured with a specialized headless screw in each tunnel.

The patellar tendon graft is tightly secured at the time of the surgery. The knee is stable enough to begin motion and weight-bearing as tolerated, as per the surgeon’s instructions.

As healing occurs, the bone tunnels fill in to further secure the tendon ends of the graft in a bone-to-bone relationship. This occurs over the next six to eight weeks.

Nice to Know:

Recent technology has led to the development of specialized absorbable screws that actually dissolve within the bone over two to three years.


  • The fixation is very strong
  • The patellar tendon replacing the ACL is as strong as the injured ACL (or even stronger).


  • A few people have mild discomfort on the front of the knee, especially when kneeling. This generally settles down within a year. Workers who kneel frequently may need to look at other graft options.
  • A normal patellar tendon has been altered. However, this does heal fully again.

2. Hamstring graft procedure

Hamstring reconstruction is an alternative to the bone-patellar-bone graft fixation and is growing in popularity. In this procedure, rather than using the patellar tendon, the surgeon uses the patient’s own hamstring tendon, either the semitendinosus or gracilis tendons from the same leg.

There are several variations of this technique. Newer hamstring fixation techniques have been developed to match and even exceed the initial pullout strength of the patellar tendon bone procedure described above. Special screws with threads designed not to cut the hamstring tendons are able to fix the tendon within the bone tunnel, as described with the patellar tendon bone technique.

In younger patients who have torn their ACLs but still have growing bones, the hamstring tendon graft is a good choice because there is less chance of damaging the ‘growth plates’- the area responsible for growth of the bone.


  • The hamstring incision is away from the patella, allowing patients to kneel comfortably.
  • The patellar tendon is left intact.


  • Soft tissue-to-bone healing occurs at a slower rate than bone-to-bone healing.
  • Unlike the patellar tendon, the hamstring tendons do not grow back after graft harvest resulting in a slight loss in hamstring strength (approximately. average of 10%) after recovery. However, most people do not notice this slight decline in strength.

3. Allograft procedure

Another option is the use of tissue from a cadaver (a deceased person) called an allograft.

Patellar tendon, hamstring tendon, or Achilles tendon allografts can be used as tissues inserted and fixed with the same techniques that are used for autografts (grafts using the individual’s own tissue).

Allografts are a good choice when the patient’s own tissue availability is limited. They are useful for complicated ligament reconstructions needing more than one graft (for example, if both anterior and posterior cruciate ligaments need to be replaced) or if both the ACL and patellar tendon are damaged.


  • No risks, pain, or scars from the donor site
  • Operative time is quicker


  • The very low risk of contracting a serious infection from the cadaver tissue. Newer techniques of tissue radiation have minimized this risk.
  • National shortage of allografts due to a high demand combined with a low supply of suitable, qualified cadavers.

Nice to Know:

Synthetic grafts

Synthetic grafts (i.e., grafts made from other materials) were commonly used in the 1970s but were generally unsuccessful.

There are currently no synthetic ligaments in the U.S. approved by the FDA for primary ACL reconstruction.

Researchers continue to try and create the perfect ACL replacement. Major requirements of a prosthetic ligament are that it must be strong, matching the compliance of a normal ACL. It must be durable, withstanding high repetitive loads without wear. It also must be perfectly tolerable to the host without bone, joint, or systemic reaction.

Risks And Possible Complications Of ACL Surgery

Any surgical procedure has possible risks and complications. 

The risks and possible complications for ACL surgery include:

  • Deep venous thrombosis (DVT)
  • Infection
  • Stiffness
  • Graft ‘impingement’

Surgeons make every effort to minimise these risks.

Deep Venous Thrombosis (DVT)

A thrombosis is a blood clot. Deep venous thrombosis occurs when blood clots form in the blood in the deep veins of the leg. It can occur after any operation, but is more likely to occur following surgery on the hip, pelvis, or knee.

A deep venous thrombosis (DVT) may cause the leg to:

  • Swell
  • Become warm to the touch
  • Become painful

Surgeons take preventing DVT very seriously. Some of the commonly used preventative measures include:

  • Encouraging movement of the leg as soon as possible after the surgery. Moving the legs gently reduces the chances of a blood clot forming.
  • Pressure stockings worn on the legs that help keep the blood in the legs moving.
  • Medications that thin the blood and prevent blood clots from forming.


The chance of getting an infection following ACL reconstruction is very low. Yet precautions are taken before and after the procedure to prevent this serious complication. Antibiotics are given intravenously just before the start of surgery and again after surgery. Proper care of the surgical incisions by the nursing staff, and thorough education about proper incision care prior to discharge from the surgical center, will limit the chance of infection. The meticulous work of the surgeon is another important factor in preventing infection.


Although rare, excessive scarring inside the knee joint after ACL reconstruction can lead to an increasingly stiff knee. Range-of-motion exercises immediately after surgery are important to prevent knee stiffness. Physical therapy is begun shortly after the surgery. Stiffness can occur if the surgery was performed too soon after the injury, when the knee was not yet able to bend through its normal range of motion. That’s why a surgeon will not reconstruct a torn ACL unless the knee is moving well.

Graft Impingement

If the drill holes in the bone (the bone tunnels that were made to hold the new ACL) are incorrectly placed, then the newly placed graft may press against the bone as the knee bends or straightens, and restrict the normal movement of the knee. Most commonly, it becomes impossible to fully straighten the knee.

Occasionally this problem may resolve with physical therapy. Usually, another arthroscopic procedure is required to shave away some of the obstructing bone to give more room for the new graft. This may not resolve the problem and further surgery may be required to drill new tunnels in order to place the graft in the proper position inside the knee.

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