Our Latest News Don't wait when you are in pain! Pinnacle now offers Orthopaedic Urgent Care Walk-ins! Monday - Friday 8AM - 4:30PM! Most insurance plans accepted. (Closed for lunch from 12PM-1PM.)
Anterior Cruciate Ligament (ACL) Tears

Anterior Cruciate Ligament (ACL) Tears

An ACL tear is one of the most common injuries. Every year a staggering 150,000 to 200,000 ACL injuries are reported. These most often occur during physical activity, but they also happen as a result of an abnormally executed everyday activity.

Even though an ACL tear has been experienced by many people, there is still very little common knowledge about it and its treatment. At our practice, we not only provide orthopaedic care but also educate the public. Therefore, here (below) our knee surgeon explains all you need to know about ACL tears.


The anterior cruciate ligament (ACL) is a thick band of tissue which has two major strands that extend from the lower leg bone (tibia) to the thigh bone (femur). It runs diagonally in the middle of the knee to provide rotational stability. Ligaments cross each other to form an "X", thus the ACL in the front of the knee crosses the posterior cruciate ligament in the back.

Therefore, when it is injured or torn, the patient feels the instability of the knee when they turn or pivot. This is particularly problematic when participating in agility sports such as soccer and football.

Normal Knee

Mechanism of Injury

Most ACL tears occur during a sporting activity and usually in younger patients. Researchshows that when you consider the number of sports hours played, ACL injuries are more common in women. There have been a variety of reasons proposed for this, such as muscle imbalance and slight variations in the anatomy of the knee joint in women compared to men. The most common sports are football and basketball in younger patients, and skiing injuries predominate in older patients.

It is, however, possible to injure the anterior cruciate doing a variety of activities. We've seen ACL tears from simple falls stepping off a curb. It can also be a work-related injury. Interestingly, most people would expect that it is due to contact, but this is not true. Mostly it is a non-contact deceleration where the athlete suddenly turns to the opposite side of the planted knee and injures it. As the patient turns and pivots the ligament tears. In basketball, it is usually a result of hyperextension and internal rotation of the tibia on the femur, associated with deceleration.

Usually, the patient will feel a sudden pop in their knee as the tear happens. Surprisingly, sometimes the knee will not get very swollen, although it certainly can. The injury is often missed because the physical examination requires great experience and training, especially when in its initial stages.

So, do not take the risk of getting misdiagnosed by going to a non-specialist. If you are suffering from a knee injury, make an appointment with our expert knee surgeon who will use their experience to diagnose you and provide you with the utmost specialist care.

torn aclNatural History of the Torn Anterior Cruciate Ligament

If left untreated the laxity, which is immediately present, only becomes worse. The other structures of the knee try in vain to provide some stability to the knee. Over time and with more usage these other structures stretch out as well, resulting in increased instability and then associated meniscal (cartilage) tears. This progresses with time because in an untreated knee the knee is unstable and produces greater stress on the cartilage. Up to 80% of the injured knees will eventually develop a cartilage tear.

The American Academy of Orthopaedic Surgeons states that about 50% of ACL injuries occur in combination with damage to the meniscus, articular cartilage (smooth lining of the knee), or other ligaments. If left untreated, this will again progressively wear at the knee, causing an increased rate of osteoarthritis development. Consequently, the patients will alter how they walk, developing a rather specific quadriceps avoidance gait. This is because when they contract their quads during normal walking it slides the tibia forward, which is usually stopped by the ACL. Therefore, the patient will naturally and unconsciously try to prevent this.

All these problems mean that the injured knee will progress to late degenerative changes and osteoarthritis much earlier than a healthy knee.

There is no substantial evidence that brace wear alone will decrease the rate of re-injury to the knee. However, for older and non-active patients, there is a significant role for non-operative treatment. By simply modifying their activities and avoiding all situations where they may pivot, older patients can reduce the risk of further damaging their knee.


The ACL is the main factor causing resistance to the anterior displacement of the tibia on the femur. This is demonstrated when the orthopaedic surgeon pulls the tibia forward on the femur, performing a test of the ACL. The tibia will displace much further forward than it should when the ACL is torn. The ligament is tight when the knee is in full extension and has the least amount of tension at approximately 45' of flexion.

Because there are different bands to the ACL, different areas of the anterior cruciate tighten at different angles of the knee. This structural complexity partially explains why ACL injuries are often missed if assessed by inexperienced physicians, or non-specialist.

Physical Examination

terrible triadExamination immediately at the time of injury will reveal at least mild swelling of the knee - but this is not always the case. Therefore, to successfully diagnose the ACL tear, a knee expert must conduct a thorough specific test. Commonly, one of the below is carried out.

Lachman Test

This is the best test. The examiner puts her hands just above and just below the knee joint. The lower bone is brought forward with the knee angled at approximately 15' and the examiner assesses the endpoint.

In a healthy knee, there is a firm endpoint with an intact ACL when the tibia is pulled forward. When the ligament is torn that endpoint is no longer present. The examiner will also look for an increased excursion of the tibia forward on the femur.

Drawer Test

Essentially, the same test as the Lachmann Test, but the knee is flexed to 90'. It is more difficult in an acute situation to perform this test because usually, the athlete's knee is too sore to allow the knee to bend to 90'.

Pivot Shift

The knee is brought from an extended position into flexion. A healthy knee will show a slight and subtle shift as the tibia rotates on the femur and shifts back into proper position. It is actually subluxed in the fully extended knee position and returns to its natural position as the knee is flexed. As it returns to its natural position there is a "pivot shift", which only an experienced knee surgeon will notice.

Associated Injuries

Associated injuries are always assessed at the same time. Joint line tenderness represents a torn cartilage and tenderness over the lateral is a symptom of collateral ligament tearing. O'Donohue's "terrible triad" injury involves not only the ACL but also the medial meniscus and the medial collateral ligament. It is unfortunately fairly common.


Originally it was believed that the knee should be repaired surgically as soon as possible. Now, most orthopaedic surgeons understand that the swelling should subside and the patient should work to improve range of motion with physiotherapy for 2-3 weeks. Once this is accomplished, our knee surgeon will advise the patient to proceed to an ACL reconstruction.

As we stated earlier, reconstruction surgery does not have to be performed on a sedentary older patient, but it is almost always recommended to younger, active patients. With modern techniques, it is performed as an outpatient operation. Thus, the patient is discharged from the hospital or surgery center the same day.

The patients will leave the hospital on crutches, advised to wear a knee immobilizer for approximately 10 days while they are getting around. When the immobilizer comes off, the patient will usually use a passive motion machine that moves the knee through flexion and extension.

Physical therapy is started immediately post-operatively. Treatment of a torn ACL in the older patient primarily focuses on physical therapy and exercise training, alongside wearing a brace for some activities.

Surgical Treatment Options

ACL Reconstruction

There have been many options described for the surgical treatment of the ACL. The most popular and currently recognized as the gold standard is an operation where the middle one-third of the patella tendon is used as a graft.

It is virtually impossible to repair a torn ligament. The torn ACL is simply removed and replaced with the patella tendon graft. Two-thirds of the patella tendon is left behind - it will repair itself without compromising the function of the knee. At each end of the patella tendon, a bone block is also taken, one piece from the tibia, and the other from the patella (kneecap). These two bony blocks are inserted into holes that are drilled into the tibia and femur and held into place with screws that provide stabilization of the ligament graft.

Most commonly the second choice for an ACL replacement is the hamstring tendon. The knee surgeon will weave the tendon into a graft close to the size of the ACL. At our practice, we have also used quadriceps tendon and allograft. An allograft is a donated cadeaver tissue that is frozen until the time of usage. Before it is used as a substitute of an ACL, it is thawed out and trimmed to size.

The advantages of an allograft operation are that there is a smaller incision required, making the rehabilitation shorter and less painful. The disadvantage is that it is not as strong as a graft formed from the patient's own tissue.

Risks, Complications and Alternatives to Surgery

Every operation, regardless of the condition of the patient being treated, comes with risks. Your surgeon will discuss all the risks with you pre-operatively, outlining the likelihood of these occurring in your particular case. Risks and complications are relatively rare, however, there is a chance that they will happen. And all have to be understood and accepted by the patient prior to the surgery.

The most common risks that come with anterior cruciate surgery are:

  • Infection

  • Blood clots in the legs

  • Failure of the graft

  • Stiffness of the knee

  • Persistent pain

  • Instability

  • Other complications: neurovascular injury and medical complications, both general and related to the anesthetic

Unfortunately, there is no way to perform any surgery without some risks, but the anterior cruciate surgery is normally 80-90% effective. Even if a complication does occur it can usually be treated and resolved.

Long Term Prognosis

With an ACL repair, the patient's long-term prognosis is excellent - if no associated significant injury has occurred.

It certainly carries a much better prognosis than when the knee if left untreated. After recovery, the patient can return to any activity that she was doing pre-operatively. And many athletes have gone on to excel again at their chosen sport.

Orthopaedic surgeon/surgery/care near me:

At Pinnacle, we utilize the most up-to-date technologies and surgical techniques to provide our patients with the highest quality orthopaedic care. We have Fellowship Trained Specialists who tackle issues from acute injuries to chronic problems. They diagnose musculoskeletal disorders including the hand, foot and ankle, trauma and fractures, joint replacement and reconstruction, sports medicine and many more.

Our orthopaedic team performs non-surgical and surgical procedures, treats sports injuries and repairs trauma to the knee, using the most advanced knowledge, treatment and methods.

We take pride in being in touch with the local community. Not only do our doctors get involved in promoting awareness at numerous schools and sporting events, but they also provide exceptional orthopaedic services at 5 convenient locations. With offices inCanton, Hiram, Marietta (East Cobb), Marietta, and Woodstock, and a Surgery Center in Woodstock,you know you can reach our knee surgeon with ease.

If you still have any questions or wish to consult a member of our staff, pleasecontactour headquarters:

  • Phone: 770-427-5717
  • Fax: 770-429-8520

  • Visit us at 300 Tower Road, Suite 101, Marietta, GA 30060

  • Make an enquire on our contact page

The material contained on this site is for informational purposes only and DOES NOT CONSTITUTE THE PROVIDING OF MEDICAL ADVICE, and is not intended to be a substitute for independent professional medical judgment, advice, diagnosis, or treatment. Always seek the advice of your physician or other qualified healthcare provider with any questions or concerns you may have regarding your health.