The pivotal role of the anterior cruciate ligament
The pivotal role of the anterior cruciate ligament
“Anything in life [could injure the ACL]. It could happen at work. It could happen with normal daily activities.” DR. MICHAEL GROSS, BOARD-CERTIFIED SURGEON WITH HACKENSACK UNIVERSITY MEDICAL CENTER AND ACTIVE ORTHOPAEDICS & SPORTS MEDICINE
Asoccer player outmaneuvers the last defender on her way to score the winning goal – and suddenly feels something go wrong in her knee. A quarterback plants his feet to send a laser to his wide receiver when a low sack catches him in the knees. A runner finishes his first 10K, and as he slows down just past the finish line, his knee gives out. Each one of them hears the same thing.
POP. POP. POP.
ACL injuries rank among the most common – and loathed – injuries in sports for professionals and amateurs alike. The extent of the injury and the treatment required can vary widely, but there isn’t a whole lot anyone can do to prevent them.
The anterior cruciate ligament, or ACL, is one of the four main ligaments in the knee. It grows out of a notch deep in the lower end of the femur, connects it to the tibia and controls rotation. The ACL and its counterpart, the posterior cruciate ligament, or PCL, form an X inside the knee.
Dr. Michael Gross is a board-certified surgeon with Hackensack University Medical Center and Active Orthopaedics & Sports Medicine. He says the ACL’s job is pretty simple. When you set your foot on the ground and rotate your body on it, the ACL makes sure your shin bone and thigh bone stay connected.
“Otherwise you’d twist right off,” he says.
Sometimes an athlete will get about as close as anyone to twisting right off. ACL injuries can strike seemingly out of nowhere, and from a number of causes. According to the American Academy of
Orthopaedic Surgeons, the main sources of injuries include: changing direction rapidly stopping suddenly slowing down while running landing incorrectly after a jump direct impact or collision That sounds – well, unfair, frankly. You can hurt yourself not by running, but by slowing down after running? More than that, Gross says you might not even realize you’ve injured your ACL.
The worst ACL damage is clear from the moment it happens. The athlete will hear a pop from their knee just before it gives out. Pain and swelling are usually immediate.
But sometimes, ACL damage isn’t so obvious. Dr. Gross says years can go by before someone notices anything amiss, especially if the ACL doesn’t tear completely. That’s because other parts of the knee, or secondary stabilizers, can compensate. “Giving-way episodes,” when the leg gives out, will become more frequent as those stabilizers can no longer make up for the damaged ACL and suffer damage themselves.
Obviously, seeking treatment if you suspect even minor ACL damage is vital.
“Let’s say you have bad brakes,” Gross says. “You don’t drive around with bad brakes and say let’s wait and see if I get into an accident.”
These days, ACL diagnosis and treatment are straightforward: Gross says patients will see their doctor for an X-ray and MRI, wait a few weeks for surgery, then spend a few months rehabilitating the knee.
Isn’t waiting to fix the knee counterintuitive? Not quite. While you don’t want to let an ACL injury linger for months or years, a patient needs three to six weeks for the swelling from a fresh ACL injury to subside before surgery is possible.
Current ACL surgery is quick and minimally invasive, though it took decades of trial and error to reach that point. Dr. Gross says in the ’60s, for example, doctors tried to repair the torn ACL. That didn’t work because it shortened the ACL, impairing the knee’s function, and required surgeons to match the pieces of countless torn strings of ligament.
“It’s like trying to sew together two mops,” Gross says.
Later doctors tried to augment the repaired ligaments with tendon grafts, until they realized the repairs still gave out while the grafts held. Now surgery involves the relatively simple matter of a tendon graft, performed arthroscopically (using small incisions rather than opening up the whole knee).
A surgeon has two options: using pieces of the patient’s tendon, either from the hamstring or patella, or using donated tendons. Gross, who performs about 150 ACL surgeries a year, says surgeons prefer the former in younger patients, because donated tendons rupture more often in patients younger than 30.
Also, a patient’s own tendon incorporates more quickly through ligamentization. In modern ACL surgery, the piece of transplanted tendon anchors deep in the femur and acts a scaffold for growing a new ligament. Gross says doctors aren’t sure how yet, but cells “just know” to grow a ligament where it needs to be, even though a tendon is there now.
After surgery, the patient can usually leave the hospital the next day. Athletes undergo four to six months of rehab before going back to “cutting” sports like tennis, volleyball or basketball, and patients can usually get back to biking or jogging much sooner.
Because there isn’t a whole lot anyone can do to prevent an ACL injury, Gross says awareness is the key to treating such a common knee injury.
“Anything in life [could injure the ACL],” he says. “It could happen at work. It could happen with normal daily activities.”
Anterior and Posterior Cruciate Ligament