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You've torn your ACL. Now what?

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A new study sheds light on treatment choices for torn knee ligaments. Surgery may not be necessary.

A 30-year-old skier takes a sharp turn on the slopes and hears a dreaded "pop" in his right knee. He has ruptured the anterior cruciate ligament (ACL)  a band of tissue that's important for stabilizing the joint. After icing, compressing, and elevating his swollen knee, he visits the doctor. Now it's time to decide on treatment.

If he's an elite athlete or has additional knee damage, the choice is fairly clear: reconstructive surgery to replace the ACL, plus intense physical therapy. But if he's a recreational skier who doesn't do many knee-stressing sports, forgoing surgery in favor of rehabilitation through physical therapy may be a sensible approach.

A study by researchers in Sweden and Denmark confirms this. The investigators followed 121 young, active adults with ACL tears, half of whom were randomly assigned to have physical therapy and surgery, while the others had physical therapy with surgery as an option later. Two years after their injuries, people in both groups had "substantial improvement" in their knee condition, and there were no major differences in five knee-related categories such as pain, other symptoms like swelling, and function in daily living and sports activities.

Of the 59 people assigned to physical therapy with surgery as an option later, 23 (about 40%) decided to have surgery within the study's two-year period while 36 (about 60%) did not.

The results suggest a wait-and-see approach may be right for some with torn ACLs and that more than half of expensive ACL reconstructions could be avoided "without adversely affecting outcomes," the investigators wrote in the July 22, 2010, issue of The New England Journal of Medicine.

The treatments for ACL tears are well-established, but the paper will probably help patients weigh their choices and remove some sense of urgency around surgery. "This has not caused a paradigm shift in what we do," says Dr. Laurence Higgins, chief of the Sports Medicine and Shoulder Service at Harvard-affiliated Brigham and Women's Hospital. "But it will add evidence and may help surgeons tell their patients, Hey wait, not everyone who has an ACL tear needs surgery. Look at this great article.'"Twist of fate

The ACL has been described as the seat belt for the knee (see illustration). It runs through the middle of the knee joint and keeps the shinbone (tibia) from sliding forward past the thighbone (femur). The ACL is one of four main ligaments in the knee  and one of the most commonly injured ones. The ACL can be stretched, torn, or both during a sudden or awkward twist, turn, or stop.

The anterior cruciate ligament helps keep the tibia from sliding forward in front of the femur.

An estimated 200,000 ACL tears occur in the United States each year, typically while people are playing sports that require sudden changes in direction (pivoting and cutting) or jumping. The sports on that list include basketball, football, skiing, soccer, tennis, volleyball, and some kinds of aerobics. Collisions aren't necessary: about 70% of ACL tears occur without direct contact with another player or object.

Although ACL tears are usually a sports injury, they do occur outside the gym and playing field. People get their ACLs torn in car crashes. A simple trip or fall that twists the knee can also result in a tear.

Anyone can damage their ACL, but female gymnasts and soccer players are especially prone to ACL tears. There are several possible explanations for women being more vulnerable to ACL injuries, including differences in muscle strength, alignment, and estrogen levels that can loosen ligaments. There's also some evidence that women are more likely than men to turn their knees inward when changing direction suddenly, placing added strain on their knees and ACLs.Tips for preventing ACL tears

For serious athletes who've torn their ACLs, a structured program to prevent re-injury is recommended. But for weekend warriors, here are three tips from Dr. Laurence Higgins for protecting your ACL:

Make a good landing. When you jump, land in a near-crouch position with knees bent and aligned straight up and down  not "knock-kneed." Viewing a video of your jumping style can help you fix it.

Strengthen the muscles around the knee. Keeping your quadriceps and hamstring muscles strong and flexible will make the knee more stable. (The "quads" form the front of the thigh, and hamstring muscles, the back.) One exercise that strengthens the quads and hamstrings is a walking lunge, which involves taking a large step forward and dropping the back knee down toward the floor, keeping the front knee over your ankle.

Keep your hip muscles strong. One-legged squats  knee bends done while standing on one leg  are an excellent way to strengthen the hips, quadriceps, and hamstrings and to improve your balance. When you do a one-legged squat, bend your knee slowly so it ends up just over your toes.

Tendon substitutes

Diagnosis of an ACL tear usually involves several hands-on tests and an MRI scan. Then it's time to choose a treatment.

Surgical reconstruction involves replacing the injured ligament with a piece of tendon taken from the person's own leg or from a cadaver. When the patient's own tissue is used, it often comes from either the patellar tendon below the knee or from tendons in the thigh. Using tissue from cadavers has become increasingly common, in part because it avoids the pain caused by removing the patient's tendon tissue. Doctors have tried repairing the ACL by sewing the torn pieces together, but that has generally proved to be ineffective.

These days, ACL surgery is usually done arthroscopically, through small incisions. That approach has shortened the recovery period, but people can still feel a fair amount of pain in the days and weeks after the operation. Months of physical therapy are needed to restore strength, coordination, and range of motion. As with all surgery, there are risks, like infection; in some cases, the operation fails to stabilize the knee.

About half of ACL tears are repaired with surgery, according to the American Academy of Orthopaedic Surgeons (AAOS). The people most likely to have the operation are elite athletes, active adults whose sports or jobs involve pivoting or hard cutting, and individuals who do heavy manual work. Replacing the torn ligament with tendon does tend to make the joint more stable than physical therapy rehab alone, which is an advantage for people who place a lot of stress on their knees. Surgery may also be the preferred route if there is additional damage to the knee  for example, if a meniscus has been torn.

Many people who get reconstructive surgery resume their pre-injury activities; the AAOS reports long-term success rates of 82% to 95%. Star athletes like New England Patriots quarterback Tom Brady, who ruptured his ACL in 2008, can come back from the injury after the operation. But according to Dr. Higgins, the joint never quite works exactly the way it did before the tear, and more research is needed to understand why.

Early-onset osteoarthritis is another common complication of ACL tears, probably caused by increased wear on the leg bones and shock-absorbing cartilage in the knee over time. It's not clear whether surgery reduces the risk of osteoarthritis.Avoiding the knife

The ACL doesn't heal on its own, but physical therapy can strengthen the muscles around the knee enough so they compensate for the nonworking ACL. A custom-made knee brace may also be useful for tennis, soccer, or other activities that involve twisting if the person plays occasionally.

Treating an ACL tear with physical therapy alone is worth considering if it's a partial tear or if the person isn't very active. Adults who are active but do "in-line" sports such as cycling or running might also do well with just physical therapy because those sports don't usually involve turning and twisting the knee.

Children and teens usually are steered toward physical therapy as the only treatment because surgery involves drilling into the growth plates of the leg bones, which may keep them from growing properly. The number of youths with torn ACLs has increased in recent years, and some blame the rising number of children playing organized, competitive sports year-round.

One big advantage of not having surgery is a faster recovery. People who don't get surgery normally recover enough to be active again within two or three months, compared with about six months for surgery patients, says Dr. Higgins. It takes longer to recover from surgery because tendon graft used to replace the ACL needs to fully heal and be ready to withstand the stress that playing sports can put on it.

The best way to treat an ACL injury can be a judgment call that factors in extent of the injury, the person's age, and his or her activities. Each situation is a little bit different. It's important to get a second opinion and carefully weigh your options.

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