Condition guide
The anterior cruciate ligament (ACL) sits in the middle of the knee, joining the thigh bone to the shin bone and stopping the knee from giving way when it twists. It usually tears during sport, on a sudden stop, a change of direction or a landing from a jump. Not every tear needs surgery: in two trials, about half of the patients who started with rehabilitation never needed an operation.
Of the two ligaments that cross inside the knee, the ACL is the one at the front; it stops the shin bone from sliding forwards and the knee from giving way as it rotates. Most injuries happen without colliding with anyone: stopping suddenly while running, twisting the body with the foot planted, or landing from a jump with the knee collapsing inwards.
The ligament may tear partly or completely, and the meniscus and other ligaments can be damaged at the same time. The diagnosis is made by examination; an MRI scan shows any accompanying injuries.
In a trial of 121 young, active adults with an average age of 26, half had rehabilitation plus early surgery; the other half started with rehabilitation and had surgery later only if it proved necessary. After five years there was no difference between the groups in knee symptoms and function; 51% of those who started with rehabilitation had had surgery by then. In a similar trial of 167 patients, those who had early surgery had a slightly higher knee score at 2 years (84.7 versus 79.4), but the researchers did not consider the difference clinically important; half of those who started with rehabilitation did not have surgery.
The picture is different for people whose injury is no longer recent and whose knee still gives way. In a trial of 316 patients, surgery gave better results than rehabilitation at 18 months (knee score 73.0 versus 64.6); 41% of those in the rehabilitation group went on to have surgery.
That is why the decision is individual. Straight after the injury it is not possible to say for certain who will do well without surgery; a few months of good rehabilitation will show it. Surgery is recommended more often for people who want to return to sports involving twisting and jumping, for those whose knee keeps giving way despite rehabilitation, and for those with an accompanying injury such as a meniscus tear. Make the decision together with your orthopaedic doctor.
Exercises at home
These exercises are for the early period after the injury and for preparing for surgery. If you have had surgery, follow the programme given by your surgeon and physiotherapist. Stop if your knee gives way, locks or swells more during an exercise.
Lie on your back and place a rolled-up towel under your knee. Press the back of your knee down into the towel to tighten the muscle at the front of your thigh; hold for 5 seconds, then relax. You can do this during painful spells too.
10 reps, 3 times a dayLie on your back. Slide your heel along the bed towards your bottom, bending your knee as far as is comfortable, then slowly straighten it. A plastic bag under the heel makes sliding easier. The aim is to bend the knee a little more easily each day and to straighten it fully.
10 reps, 3 times a dayLie on your back and bend your other knee. Tighten your thigh and, keeping your knee straight, lift your leg up to the level of your other knee; hold for 2–3 seconds, then lower it slowly.
10 reps, 2–3 setsLie on your back with your knees bent and feet on the floor. Squeeze your buttocks and slowly lift your hips, hold for 2–3 seconds, then lower.
10 reps, 2 setsLean your back against a wall with your feet one step out from it. Slide your back down the wall, bending your knees no further than a half squat; hold for a few seconds, then come back up. If the pain increases, bend less.
8–10 reps, 2 setsHolding on lightly to the kitchen counter, stand on one leg with your knee slightly bent. As it gets easier, hold on less.
30 seconds, 3 times on each legMove on to running, jumping and change-of-direction work only after your physiotherapist has measured your knee strength and balance, and under their supervision.
Video
From the YouTube channel of US physical therapists Bob Schrupp and Brad Heineck.
Two physiotherapists explain the injury and the treatment options.
Movements to get the knee straightening and bending fully again.
A completely torn ligament is generally not expected to regain its former strength by itself. But with strong thigh and hip muscles and good balance control, the knee can work without trouble in many people even without the ligament. In the trials, about half of those who started with rehabilitation never needed surgery.
Many people can keep up sports that do not involve twisting, such as running in a straight line, cycling and swimming, without surgery. In sports with sudden turns and jumps, such as football, basketball or skiing, the risk of the knee giving way is higher; surgery is recommended more often for those who want to return to these sports. If your knee gives way, stop that activity and consult your doctor.
Most programmes aim for at least 9 months. In one study, for each month that the return to sport was delayed within the first 9 months, the reinjury rate fell by 51%. Measurement matters as much as time: in strength and hop tests, your injured leg should be close to your healthy one.
No. In a review combining 69 studies (7,556 people), 81% of those who had surgery returned to some kind of sport, 65% to their pre-injury level and 55% to competitive sport. Younger age, both legs performing evenly in hop tests and feeling psychologically ready to return make it more likely.
See a doctor without delay if you have any of the following:
Sources
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