Anterior Cruciate Ligament (ACL) Injuries
OverviewCruciate ligaments are made of many strands and function like short ropes that hold the knee joint tightly in place when the leg is bent or straightened. This stability is needed for proper knee joint movement.
The name, cruciate, derives from the word crux, meaning cross, and crucial. The cruciate ligaments not only lie inside the knee joint, they crisscross each other to form an "x". The cruciate ligament located toward the front of the knee is the anterior cruciate ligament (ACL), and the one located toward the rear of the knee is called the posterior cruciate ligament (PCL).
The ACL prevents the shinbone from sliding forward beneath the thighbone. The ACL can be injured in several ways:
- changing direction rapidly
- slowing down when running
- landing from a jump
- direct contact, such as in a football tackle
If you walk or run on an injured ACL, you can damage the cushioning cartilage in the knee. For example, you may plant the foot and turn the body to pivot, only to have the shinbone stay in place as the thighbone above it moves with the body.
If you injure your ACL, you may not immediately feel any pain. However, you might hear a popping noise and feel your knee give out from under you. Within two to 12 hours, the knee will swell, and you will feel pain when you try to stand. Apply ice to control swelling and elevate your knee until you can see an orthopaedic surgeon.
A diagnosis of ACL injury is based on a thorough physical examination of the knee. The exam may include several tests to see if the knee stays in the proper position when pressure is applied from different directions. Your orthopaedist may order an x-ray and MRI (magnetic resonance imaging) scan or, in some cases, arthroscopic inspection to determine the extent of damage to your ACL.
The physical examination for ACL instability tests for abnormal motion of the tibia in relation to the femur. The most reliable indicator of an ACL injury is a strongly positive Lachman test, but inaccurate results may be obtained if the examiner is unskilled or if the knee is painful and swollen. The Lachman test measures how far the shin can be displaced forward in relation to the thigh. In some cases, an arthrometer such as the KT-1000 may be used to quantify joint laxity (looseness).
A large effusion (bleeding into the joint) often accompanies an ACL injury. In 50 to 70 percent of cases of acute hemarthrosis (blood in the joint), an ACL injury is involved.
Initial TreatmentInitial treatment includes rest, ice, compression, and elevation (commonly known as "RICE"); a brace to immobilize the knee; crutches; and pain relievers. Get to your doctor right away to evaluate your condition.
Treating ACL TearsTreatment may be nonsurgical or surgical, depending on your desired lifestyle. The question is not so much your level of activity in the past, but expectations for the future. Sedentary people and recreational athletes who are prepared to modify their activities to avoid further knee problems may opt for conservative nonsurgical treatment.
Ninety percent of patients who are willing to adapt to relatively sedentary lifestyles and avoid activities that cause the knee to give way can be managed nonsurgically. Only about 10 percent of sedentary patients have symptoms of instability with activities of daily living.
Nonsurgical therapy consists of a period of protective bracing with progressive return to range-of-motion and muscle-strengthening exercises. The goal is to create natural stability for the knee by developing the quadriceps and hamstring muscles.
However, if your goal is to continue an active lifestyle, surgery may be the treatment of choice because a torn ACL does not heal.
Reconstructive SurgeryIf you will need reconstructive surgery, your doctor will most likely replace the damaged ACL with strong, healthy tissue taken from another area near your knee. A strip of tendon from under your kneecap (patellar tendon) or hamstring may be used. Your doctor threads the tissue through the inside of your knee joint and secures the ends to your thighbone and shinbone. We like to do a biological reconstruction of the ACL, where we use one of the hamstring tendons and thread the tendon through the previous torn ACL, removing as little of it as possible. By doing so, we use smaller tunnels in the bones, leading to less bony problems. Also by preserving the original torn ACL, the knee obtains better proprioception (the knees feeling in space) post-operatively.
Successful ACL reconstructive surgery tightens your knee and restores its stability. Progress is assessed by your perception of how stable the knee feels and by comparing the strength and stability of the injured and uninjured knees. The ultimate goal of ACL reconstructive surgery is to provide dynamic stability while maintaining full range of motion. Another goal of this surgery is to help you avoid further injury thereby preserving meniscus and articular cartilage, and return to an active lifestyle.
In the United States, doctors see more than 95,000 ACL tears each year and perform about 50,000 ligament reconstruction procedures. The surgeries are successful about 85 to 92 percent of the time.
After surgery, soft tissue needs time to heal before exercise can begin. While in the hospital, patients start partial weight bearing with exercises to re-establish knee joint mobility and normal gait. They wear a brace and use crutches for the first six weeks.
A physical therapy program usually begins with range-of-motion and progressive resistive exercises, then incorporates power, aerobic and muscular endurance, flexibility, and coordination drills. Finally, patients develop speed and agility through sport-specific exercise routines. A typical patient may begin to ride a bike at three months, start running at five to seven months, and return to competitive sports after eight to 12 months. Full recovery may take up to two years.
Preventing ACL InjuriesAthletes can take three steps to reduce their risk of ACL injuries:
- Training and conditioning should be year-round activities. Skill drills and strength and flexibility exercises will enhance balance and coordination so you will be ready when the season starts.
- Strength training for hamstring and quadriceps muscles should be a regular part of your conditioning program. To stretch the quads, stand and use a wall or table for support. Lift one leg and pull your foot towards your buttocks. Hold for five seconds, then release the foot and stand straight. Repeat six to ten times on one side, then turn and repeat on the other side. To stretch the hamstrings, sit with one knee bent and the other leg extended, toes pointing to the ceiling. Lean forward until you feel a stretch. Hold for five seconds then return to your original position. Repeat six to ten times on each leg.
- Practice proper landing technique (from a jump) and learn to do cutting maneuvers in a crouched posture with a slight bend at the knee and the hip.
Improving Sports PerformanceThe key to improving sports performance after an ACL injury is a proper rehabilitation program, and adhering to some of those same principles following the injury. Keep in mind that the single most important aspect of improving performance is stretching before and after you step onto the field, court, ice, or golf course.
Benefits derived from stretching include:
- increased physical efficiency and performance
- decreased risk of injury
- increased blood supply and nutrients to joint structures
- increased coordination
- improved muscular balance and postural awareness
- decreased risk of lower-back pain
- reduced stress
- enhanced enjoyment
RehabilitationAs an athlete, your number one concern is getting back to full strength as soon as possible so that you can return to training and competition. That is why appropriate rehabilitation is extremely important. Rehabilitation for an ACL injury, a common knee injury in football and basketball, often includes the following:
- reduce activity during the acute phase
- ice injury multiple times per day
- compression of the injured knee with a secure wrap or ACE bandage
- elevation of the injured knee above heart level
- use anti-inflammatory medications such as ibuprofen to reduce inflammation and speed up recovery
The objectives of rehabilitation from an ACL injury are to increase hip and knee flexibility, establish pain-free range of motion, and strengthen the thigh muscles. In the case of severe injury, you should completely avoid activity that causes knee pain. In these cases, you can maintain cardiovascular fitness by swimming or cycling unless otherwise prescribed by your doctor. Rehabilitation of an ACL injury is different when the knee injury requires surgery (or reconstruction). In these cases, your doctor will prescribe physical therapy.
In some of the following rehabilitation exercises, both legs are to be exercised, which is intended to prevent the uninjured leg from developing anterior knee pain. (The uninjured leg is forced to assume some of the workload of the injured one and so is prone to injury.) It's best to perform these exercises three times a day. It is important that you gradually work up to this amount.
- Front thigh muscle sets
Sit with legs extended and fully contract the muscles of the front thighs. Hold contractions for 10 seconds. Repeat 10 times.
- Straight-leg raises
Lie with one leg extended and the other bent at the knee. Lift the entire leg from the hip so that the heel is about 5 inches above the floor or ground. Hold this position for 5 to 10 seconds and then slowly lower the leg. Repeat 10 times for each leg.
- Backward leg raises
Lie on stomach with legs straight. Lift one leg as high as possible and hold for 5 to 10 seconds. Repeat 10 to 20 times for each leg.
- Half-knee bends
Stand with feet at about shoulder width apart or as the injury improves, try to stand with feet together. Slowly lower the body weight by bending the knees. Do not perform a full squat but rather stop at about half of the full-squat position and then fully extend the knees. If there is pain before achieving the half-squat position, stop downward travel at that point. Repeat 10 to 20 times.
Once ACL pain has been minimized, you may swim, cycle, walk, stair climb, weight train, or jog, as pain allows. These activities will help you to gradually return to full training. Also remember to continue these stretching, strengthening, and range-of-motion exercises in order to reduce the risk of injury recurrence.
Alternative exercisesDuring the period when normal training should be avoided, alternative exercises may be used. These activities should not require any actions that create or intensify pain at the site of injury. They include:
- water running
- stationary bicycle (add resistance gradually from one session to the next, as pain allows)
Rehabilitation after surgeryAn athlete who wishes to return to sports that involve jumping, cutting, and pivoting may need surgery to repair the ligament. This stabilizes the knee, preserves the cartilage, and enables a return to sports at the same level as prior to the surgery. After surgery, exercise and rehabilitative therapy are required to strengthen the muscles and restore mobility. With this procedure, most athletes can return to their chosen sport at the same level.
- Keep in mind that if your ACL injury requires surgery, the soft tissue needs time to heal before exercise can begin. While in the hospital, patients start partial weight bearing with exercises to re-establish knee joint mobility and normal gait. In these cases, you would be required to wear a brace and use crutches for the first six weeks.
- A physical therapy program usually begins with range-of-motion and resistive exercises, then incorporates power, aerobic and muscular endurance, flexibility, and coordination drills.
- Finally, patients develop speed and agility through sport-specific exercise routines. A typical patient may begin to ride a bike at three months, start running at five to seven months, and return to competitive sports after eight to 12 months. Full recovery may take up to two years.
- The ultimate goal of ACL reconstructive surgery is to provide dynamic stability while maintaining full range of motion, so that athletes can return to competitive or recreational sports. Progress is assessed by the patient's perception of how stable the knee feels and by comparing the strength and stability of the injured and uninjured knees.
When can I return to my sport or activity?The goal of rehabilitation is to return you to your sport or activity as soon as is safely possible. If you return too soon, you may worsen your injury, which could lead to permanent damage. Everyone recovers from injury at a different rate. Your return to activity is determined by how soon your ACL injury recovers, not by how many days or weeks it has been since your injury occurred. It also depends on how serious the injury is. Instances where reconstructive surgery is required will obviously create a longer recovery period than patients with a strain or anterior knee pain.
A good rule is to allow pain to dictate when you're ready to return to activity. You should return in moderation, and back off if you feel any pain.
The ultimate goal of ACL reconstructive surgery is to provide dynamic stability while maintaining full range of motion, so that athletes can return to competitive or recreational sports. Progress is assessed by the patient's perception of how stable the knee feels and by comparing the strength and stability of the injured and uninjured knees.
You may safely return to your sport or activity when, starting from the top of the list and progressing to the end, each of the following is true:
- You have full range of motion in the injured knee compared to the uninjured knee.
- You have full strength of the injured knee compared to the uninjured knee.
- You can jog straight ahead without pain or limping.
- You can sprint straight ahead without pain or limping.
- You can perform 45-degree cuts, first at half-speed, then at full-speed.
- You can perform 20-yard figures-of-eight, first at half-speed, then at full-speed.
- You can perform 90-degree cuts, first at half-speed, then at full-speed.
- You can perform 10-yard figures-of-eight, first at half-speed, then at full-speed.
- You can jump on both legs without pain and you can jump on the injured leg without pain.
How long will the effects of the injury last?With proper rehabilitation, a first occurrence of pain that is diagnosed and treated in its early stages with rest, ice, elevation, and compression usually lasts two weeks. If the injury has recurred several times, full recovery may take as long as six weeks.
If poor biomechanics are the underlying problem, returning to your sport may take longer. Some athletes with anterior knee pain caused by poor biomechanics of the foot, knee, or hip, find immediate relief from pain once fitted with appropriate and effective orthotic devices or patella tracking braces.
Frequent episodes of ACL injuries may result in a ligament tear. Such a complication may require surgical treatment, and full recovery under such circumstances can take up to two years, depending on the severity.