Anterior Cruciate Ligament (ACL) Injuries

Updated 02/21/2015
Written and edited by Aruna Seneviratne, M.D.

Several ligaments stabilize the human knee. They are the Anterior Cruciate Ligament (ACL), the Posterior Cruciate Ligament (PCL), the Medial Collateral Ligament (MCL), the Lateral Collateral Ligament (LCL), and the Posterolateral Corner Complex (PLC). Injury to the ACL is can lead to instability of the knee. Injuries to the ACL can occur in isolation or in combination with other injuries - usually ACL, LCL, and PLC injuries. Meniscal tears can also occur concurrently. These injuries typically occur during participation in sports that involve lateral movements such as soccer, skiing, football, etc. Women have a 5-7 fold increased risk of ACL ruptures and it is hypothesized that its due to anatomic variations, neuromuscular control mechanisms, and other factors. Hormonal differences have been largely disputed through rigorous scientific study, including a study published by Dr. Seneviratne investigating the influence of estrogen on ACL tenocyte function ( Seneviratne AM, Attia E, Williams RJ, Rodeo SA, Hannafin J."The Effect of Estrogen on Ovine Anterior Cruciate Ligament Fibroblasts: Cell Proliferation and Collagen Synthesis." American Journal of Sports Medicine, November 2003).

Symptoms:
ACL tears can lead to knee instability, and that may lead to microscopic damage to the articular cartilage (the smooth articulating surface of joints), which in turn may lead to osteoarthritis in the future. There are two categories of patients - copers (10% of patients) and non-copers. Copers are able to continue with their activities of daily living and sports without having instability of the knee. These patients have very strong hamstring muscles that compensate for the lack of an ACL. Non-copers have overt knee instability with sports, and sometimes with simple walking. Knee pain usually resolves after about 3 weeks of the injury, and patients can generally walk with without too many symptoms.

Biology: Why does it occur?
These injuries occur due to high-energy trauma - motor vehicle accidents or sporting injuries. They require prompt medical attention. The LCL and PLC are outside the knee joint and have greater healing potential than the PCL which is inside the knee joint. Therefore, early repair of the LCL and PLC have been advocated to make use of this healing response that occurs within the first three weeks from injury. The PCL tends to demonstrate less robust healing, and late reconstruction is advocated.

Common Diagnostic Techniques:
History: Diagnosing the problem begins with a detailed history that your surgeon will obtain from you.
Physical Exam: A thorough physical examination is then conducted by your surgeon.
X-Rays: Plain radiographs (X-Rays) are the most important diagnostic study that is performed initially. For the knee your surgeon will obtain specialized views. Usually these are weight bearing x-rays - i.e.: you will be standing for the x-rays.
MRI: Your surgeon may obtain additional studies such as an MRI to look more closely at all ligaments and soft tissues

Treatment:
Depends on a variety of factors including patient age, activity level, degree of instability etc. Older patients are usually treated non-operatively with physical therapy. Athletes who play high demand sports such as basketball, soccer, football, and skiing, require surgical reconstruction of the ACL. Dr. Seneviratne will carefully evaluate each patient and recommend the optimum course of treatment.

ACL Surgery
Surgery is performed arthroscopically, with a small incision on the front of the knee to harvest the graft. The graft can be the central third of the patella tendon, or the hamstrings. The graft is placed through 2 precisely placed tunnels in the tibia and femur, and fixed with titanium screws, thereby reconstructing the ligament in an anatomically accurate fashion. Surgery takes about 60-90 minutes, and is an outpatient procedure where the patient goes home the same day. Dr. Seneviratne performs a footprint ACL reconstruction using flexible reamers and the anteromedial portal technique.

After Surgery
You will be placed into a brace, and you are allowed to weight bear as tolerated. You will start range of motion exercises of the knee immediately. Physical therapy is started usually on post op day one, but most definitely within 1 week of surgery for edema control, muscle activation, and other modalities to aid healing. Rehabilitation for this type of injury can last up to 6 months.

FAQ's
Where can I get more information on the surgery and its rehabilitation protocol after surgery?
Dr. Seneviratne has a detailed booklet on this topic.

What are the risks of ACL reconstructive surgery?
Infection, bleeding, damage to nerves and blood vessels, blood clots that form in your legs (DVT), blood clots that can break off and travel to your lungs causing a pulmonary embolus (PE). Knee stiffness is an additional risks.

Is quadriceps weakness a permanent problem?
Permanent quadriceps weakness may occur in about 20 percent of patients undergoing ACL reconstruction - regardless of graft choice. A variety of factors are responsible for it including the use of a femoral nerve block at the time of surgery, inadequate rehabilitation post operatively, and other factors.

What are the graft choices for ACL reconstruction?
ACLs can be reconstructed using your own tissue - the central third of the patellar tendon with two bone plugs harvest from the patella and tibia or hamstring tendon. Allograft tissue (cadaveric tissue harvested at time of death) can also be used. Dr. Seneviratne prefers to use the patient's own tissue as it heals faster and eliminates the risk transmitting diseases such as HIV or Hepatitis B although those risks are very remote. There is a role for allograft use, and Dr. Seneviratne will evaluate each patient and customize treatment for the patient.

What is the re-rupture rate of a reconstructed ACL?
For bone patellar tendon bone autograft ACL reconstructions - 3%
For hamstring ACL reconstructions - 4-13%
For allograft (cadaver tissue) ACL reconstructions - about 20%

How long is the recovery period?
Early healing is 6 weeks. Full and mature healing can take upto 1 year. Most professional athletes are out of sports participation for a whole year. However, most patients walk without a limp at about 6-8 weeks, and can jog on a treadmill at 8 weeks post op.

Can I return to my pre-injury level of play?
Yes. Many professional athletes have returned to their previous level of play - Peekaboo Street - won gold medal in skiing, Tom Brady - quarterback for New England Patriots won superbowl after ACL reconstruction.