So, what is the ACL? The anterior cruciate ligament is the primary stabilizing ligament in the knee. Coupled with the posterior cruciate (PCL), medial (MCL) and lateral (LCL) collateral ligaments, the knee is supported statically throughout the entire range of motion. These ligaments attach the femur to the tibia and move as the knee does, helping to prevent the knee from buckling when cutting quickly to make a challenge, supporting the plant leg when striking the ball or helping keep the knee locked when slide tackling.The medial and lateral meniscus also lend support to the knee. Remarkable structures these ligaments, but prone to injury when enough force occurs during an awkward position in space. Surprisingly, over 75% of ACL injuries occur as a NON-contact event, ie, the ACL “blows out” just from landing awkwardly , cutting too quickly or just decelarating. Contact injuries almost always damage multiple structures and may be career threatening !
What is so devastating for females is that across all sports, they have a 4-8 times increased liklihood of tearing their ACL compared to young men! Many theories exist as to why our young ladies are more prone to ACL tears. There are internal and external risk factors at work. Abnormal posture, lower extremity alignment, size of the ACL, width of the notch (the space inside the knee that “houses” the ACL) ,hormonal issues, and just the simple way they jump and land have all been implicated as internal factors intrinsic to women. Kinematic studies have shown that women tend to be more quadriceps active, ie , during landing from a jump, many show a straight knee at impact. With that, the center of gravity may be too high and cause a hyperextension to occur at the knee, thrusting the body forward and causing the ACL to rupture. Studies have shown that “training” females to land with a flexed or bent knee, ie , hamstring active, has reduced the number of ACL tears. (This will be discussed further in Preventing ACL injuries).Fatigue and deconditioning also play a role in many ACL injuries. External factors are similar for males and females and include footwear, playing surface and weather.
So what happens when you tear your ACL? The “pop” that is often heard is yet to be explained. It may be the sound of the ligament tearing or the uncoupling and coupling of the knee joint. MRI studies show bone bruising to occur in most ACL tears so the concussive force of the femur striking the tibia may be the sound but no one is certain.
After the tear, and depending on associated injuries to the knee, knee pain and swelling are most common. Swelling often leads to stiffness, ie, it is hard to straighten or bend the knee. However despite the stiffness, if a wrong turn occurs again, the knee will buckle, give way, or give out, as a result of the femur and tibia being relatively disconnected. Some can walk and bear weight with a limp, others need crutches.
Immediate action must be taken! PRICE should be heeded…Protect with crutches or brace, Rest, Ice, Compress with ACE wrap and Elevate! See a physician with sports knowledge to prevent a delay in diagnosis. A thorough exam may be difficult when first seen due to pain and guarding. But with gentle reassurance I can often elicit enough signs to decide if the ACL is damaged. An Xray should be done to see if growth plates are open and whether a fracture has occurred. Any suspicion of an ACL tear and a MRI should be the next step.
If the diagnosis is confirmed by MRI, surgery in the young athlete is indicated to prevent long term damage to the knee. This is especially important if the meniscus is torn or loose bodies are seen which may represent severe cartilage damage to the joint. If the growth plates are open and menses not yet begun,, signifying further growth potential, surgery is risky and somewhat controversial. Most of us will wait til growth has stopped and procede with therapy to regain motion and strength. Sports activities should be limited and bracing for some daily routines may be needed. If the growth plates have closed or there has been no increased height over the prior 6 month period, then surgery can be safely performed WHEN full range of motion has returned and balance has improved. Premature surgery in the face of a stiff knee may lead to a condition known as arthrofibrosis with devastating consequences.
The ACL cannot heal intrinsically and therefore all ACL surgeries (unless a fracture of the eminence of the tibia is found), requires a reconstruction, ie , replacement of the native ACL with a new tissue graft. Surgical options exist including harvesting the patients own tissue (autograft) :patellar tendon with bone plugs, quadriceps tendon with or without bone plug or hamstrings or using cadaver tissue (allograft) of which many options exist.Pros and cons are cited for ALL treatment options and a thorough preoperative discussion is imperative.( The scope of these issues is too advanced for this article)
Surgery is performed as an outpatient under anesthesia (general, spinal, sciatic-femoral block) and generally takes about an hour. . Associated injuries are generally reapired at the same setting. After surgery a brace and crutches are used and simple exercises may be prescribed. A CPM (continuous passive motion) machine may be helpful. After the first postoperative office visit, I send my patients to a physiotherapist who will oversee the return of function in the knee. Rehabilitation programs are well known and the patient progresses through closed and open chain exercises during which time progressive range of motion, strength and agility and conditioning return. The average patient will return to some sporting activity AFTER 6-9 months, a rare exception will return earlier and some will return after a full year. Some NEVER return. The reasons are many.
Motivation and compliance with therapy are the key to success. Good to excellent outcomes will occur in over 90% of our patients. Complications such as graft failure can occur. Infection and blood clots may also be an issue but fortunately are uncommon.
Long term unfortunately the results do deteriorate. In a group of soccer players with and without ACL tears, the average time to playing competitively is cut in half for those having had ACL reconstruction. some of us wonder if we should EVER allow our youngsters to return to sports after an ACL repair. After all the goal is to stabilize the knee to prevent premature meniscus damage and arthritis. If we send them back out are we jeopardizing their long term knee health….food for thought. There is NO doubt that the ACL should be reconstructed in our young ladies, but return to sports is an ethical topic best dealt with your surgeon.