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Anterior Cruciate Ligament (ACL)


The Injury
The anterior cruciate ligament (ACL) is an important stabilizing ligament of the knee. It is located deep inside the knee joint and provides almost 90% of the stability to forward force on the joint. Injuries to this ligament are very common in aggressive sports such as skiing and basketball . Injury to the ACL usually occurs with a sudden hyperextension or rotational force to the joint. The exact mechanism differs for different sports. Typically the injured athlete will hear or feel a “pop”, and will have sudden onset of pain, instability and swelling. If this scenario occurs, the athlete should not attempt to continue playing, and should seek medical attention. Because the ACL is such an important stabilizer of the knee, injury to the ligament makes it difficult to participate in aggressive twisting sports. It should be emphasized that certain sports can continue to be performed quite well without an ACL. These are “straight ahead” sports such as bicycling, roller rollerblading, light jogging and swimming. Twisting, cutting and jumping sports are not recommended however due to the risk of the knee giving way. The knee is designed to work as a hinge, moving in one plane. With a torn ACL, there is increased play in the joint allowing shearing forces across the cartilage surface, and leading to progressive tearing of the cartilage discs (menisci) and breakdown of the joint surface. Over time, this breakdown leads to degenerative arthritis.

Treatment Options
Treatment of ACL injuries has come a long way in the past ten years. Today athletes have greater than a 90% chance of returning to their pre-injury level of sports participation.

Conservative care is recommended for minor and partial tears of the ACL, or tears in which the knee is still within the accepted limits of stability (less than 3mm of laxity). Non surgical treatment is also recommended for the patient who is willing to modify their activity to non twisting less aggressive sports. In these athletes, we begin an immediate specialized rehabilitation program, and provide a custom fitted knee brace for use during sports activity.

Surgical Options
Surgery for ACL injuries is extremely specialized and should only be performed by a surgeon who specializes in this type of injury. The techniques continue to change and only someone on the cutting edge can hope to stay up with all of the latest changes. Your surgeon should perform at least 50 of these operations a year.

  • The current state of the art recommendations:
  • The surgery should be entirely arthroscopic.
  • Associated surgeries such as meniscus repairs should be done arthroscopically.
  • Immediate weight bearing should be allowed following surgery.
  • Accelerated rehabilitation. (Motion begins immediately)

Surgical Technique

Suture Repair of the ACL

This is rarely the best choice for this injury, but is recommended in certain rare situations when the ligament is torn off its attachment site, but is still intact and not stretched out, or when it tears off with a fragment of bone. In most situations it has been proven in many scientific studies that repair is much less predictable of a good outcome than a full reconstruction.

This means creating a new ligament out of a tendon from another location in the patient’s knee or using cadaver tissue. There are three popular choices for the choice of tissue:

Patella Tendon (Autograft)
This means taking a strip of the tendon from the front of the athlete’s own knee (autograft), and is the most popular choice for this surgery. This technique has been utilized for the longest period of time in the largest number of patients, and is considered the gold standard for ACL reconstruction. We have utilized this technique in hundreds of patients with superb results and recommend this as the best choice for the majority of athletes.

Advantages: Strong graft, with bone attachments at each end, which allows the graft to be fixed very solidly at the time of surgery and which allows healing to the body in the shortest period of time (bone to bone healing) of 4-6 weeks.

Disadvantages: Requires taking tissue from the body. This may cause donor site soreness in a small percentage of patients. To avoid this we utilize a unique method for harvesting the patella tendon graft. This method utilizes a round oscillating tool, which takes a circular graft and leaves the patella with a smooth defect. This makes the patella much less prone to any post surgical problems, and we have not found this to be a problem in many hundreds of patients.

This is a newer method, that is gaining popularity. We recommend this technique for patients who for whatever reason are not a candidate for usage of the patella tendon.

Advantages: For some surgeons, this may result in a lower incidence of donor site discomfort. We have not found this to be the case.

Disadvantages: Hamstring tendons do not come with bone attachments, and it takes the body 12 weeks to heal the hamstring graft (3 times as long as the patella tendon). This means that in the early postoperative period the graft is at risk for injury for a longer period of time.

This means using tissue from a cadaver. This is an attractive option for patients who want the least pain post surgery or in cases where multiple ligaments are injured and additional tissue is needed for surgery, or for revision cases where the patient’s own patella tendon has already been utilized.

Advantages: No need to take tissue from the patients already injured knee. May be a good idea in the older patient whose own tissue may be weaker than the usually young donor.

Disadvantages: There is approximately a 1/1,000,000 chance that a disease can be transmitted with a donor graft despite careful laboratory screening.

New Frontiers
ACL Tightening (Shrinkage) : We are currently performing a study utilizing a new technique which tightens the partially torn or stretched ACL. This is not applicable to the completely torn ligament. Surgery is done arthroscopically with no incisions. Recovery time is dramatically faster than with a reconstruction. Initially, we were impressed with the ability to tighten the ligament at the time of surgery (average 50% reduction in laxity). However, after studying these patients for 5-years, many appear to stretch out. (Publication PDF, 111KB) We are currently studying a new method of ACL shrinkage that appears to be more promising.

Patients are sent home with a knee brace for the first day. Range of motion is started as soon as the wound is checked. Early goals are to obtain range of motion and to reeducate the muscles. Weight bearing is begun immediately with crutches. The brace is utilized for three weeks or until the quadriceps are strong enough to support the limb. Crutches are discontinued after 1-2 weeks. Stationary bicycling is begun as soon as the patient can achieve 100 degrees of flexion and can get around on the pedal (usually 2 weeks). Outdoor bicycling and jogging are allowed at 3 months. Return to twisting cutting and jumping sports is delayed for 6 months since this is how long it takes for the graft to biologically heal. Prior to returning to sports, the patient is expected to have regained 90-95% of their muscular strength.

ACL reconstruction is a highly successful operation. 90-95% of patients can be expected to return to full sports participation with 6 months and with aggressive rehabilitation.


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San Francisco, CA 94115
Phone: 415-923-0944
Fax: 415-923-5896

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