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ACL Injuries 101
Anterior Cruciate Ligament (ACL) knee injuries occur most often in athletes. The most common mechanism that tears the ACL is the combination of a sudden stopping motion on the leg while quickly twisting on the knee. This can happen in a sport such as basketball, for example, when a player lands on the leg when coming down from a rebound or is running down the court and makes an abrupt stop to pivot. In football, soccer, or lacrosse, the cleats on the shoes do not allow the foot to slip when excessive force is applied. In skiing, the ACL is commonly injured when the skier sits back while falling; the weight of the body quickly shifts backward, applying too much force to the knee, causing the ACL to pop. A contact injury, such as when the player is clipped in football, forces the knee into an abnormal position. This may tear the ACL, MCL, and other structures, all at once.
Recent research has found that women are nearly three times more likely to have ACL injuries than men, with some statistics saying female soccers are at an 8x greater risk of injuring their ACLs compared to male soccer players. While the exact mechanic of this higher risk level is not completely clear, researchers believe it may be due to several differences between females and males, including: hormone levels on ligament strength and stiffness, neuromuscular control, lower limb biomechanics, and ligament strength and fatigue. The most common findings have shown differences in neuromuscular control and strength in women, with less hip and knee flexion compared to men. This can cause individuals to land in a valgus position, also referred to as valgus collapse and knock knee. While more common in women, they are not alone in this: just look at Robert Griffin III's ACL tear in 2012.
ACL injuries range from a simple sprain to partial or complete ligament tear. When the ACL tears, the person feels the knee go out of joint and often hears or feels a “pop”. If he or she tries to stand on the leg, the knee may feel unstable and give out. The knee usually swells a great deal immediately (within two hours). Over the next several hours, pain becomes more severe and it becomes difficult to walk.
The best treatment following an acute ACL injury is to usually protect the joint and apply ice, along with the use of crutches for several weeks. As the swelling and pain subside, and the patient can put weight on the leg, the immobilizer and crutches can be discontinued. The emphasis is then placed on regaining lost knee motion. During this time, resistive exercises to build up strength should not be done, in order to prevent sustaining any further damage.
Some patients can function well even if the ACL is torn. However, it may be necessary to modify activities and avoid high-risk sports (such as basketball, soccer, and football). The key to preventing the knee that has a torn ACL from giving out is to avoid quick pivoting motions. Wearing a knee brace can help prevent re-injuring the knee, but not for the reasons you may think. The main effect a knee brace has is as a constant reminder to be careful. While it offers some support, a brace will not completely stabilize a knee that has a torn ACL. Exercises that restore muscle strength, power, coordination, and endurance will also improve knee function and help stabilize the knee. However, a fully rehabilitated knee that has a torn ACL can still give way if a quick change in direction is unexpected.
There may be instances when immediate surgery is indicated following injury, such as a knee dislocation when multiple ligaments are torn. Tears of the outer knee ligaments (lateral collateral ligament) often do require surgical repair. Individual decisions need to be made on whether or not to reconstruct the ACL soon after injury in these instances where immediate surgery may be required.
During ACL reconstruction surgery the surgeon sews the torn ligament back together using graft tissue. The surgery lasts approximately two hours and is done through small incisions. Two holes – one in the femur and one in the tibia – are drilled and the “new” ACL graft is anchored to the bones with graft-stabilization hardware. This fixation hardware remains in the knee and is not felt by the patient.
Dr. Peyton comments, “I use the double looped hamstring graft fixed with the EZ-loc and Washerloc technique because it is the strongest fixation. This procedure leaves a more cosmetic scar, allows for an earlier rehab, and for patients to return to sports sooner.” This procedure allows for a faster recovery time, allowing some patients to return to full exercise after 6 months instead of 1 – 1 ½ years after surgery.
Within two or three weeks after surgery, the patient is usually walking on level surfaces without a brace or crutches. At about five or six weeks, he or she can usually go up and down stairs without support. For the next several months, exercises are done to regain motion in the knee. When the knee has full range of motion (usually at six to eight weeks), muscle-strengthening exercises are done. At six months, the patient is usually running and at nine months, participating in sports.
Athletes can reduce their risk of ACL injuries by performing training drills that require balance, power, and agility. Adding plyometric exercises, such as jumping, and balance drills help improve neuromuscular conditioning and muscular reactions and ultimately shows a decrease in the risk of ACL injury. Many team physicians now routinely recommend an ACL conditioning program, especially for their female players 2-3 times per week.
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