Rehabilitation after a torn ACL injury

How long the healing process and rehabilitation take depends in part on the extent of injury, whether surgery was done and, if so, which tendon was used to replace the ACL. Physical factors like your age and fitness level influence the healing process too.

The healing process after ACL surgery typically involves the following:

• The surgical stitches are removed after about 2 weeks.
• You can return to work after about 4 to 6 weeks. If you have a physically demanding job, it takes longer.
• After about 6 to 8 weeks, it’s possible to use an exercise bike (if you can bend your knee far enough without any trouble).
• Light jogging is possible after about four months.
• You can gradually return to doing sports after about six months.

Many experts recommend waiting nine to twelve months before starting intense ball sports and martial arts again. Sometimes it takes even longer to get to that point. It is important not to overdo it, and to start new activities slowly and carefully. If you're not sure, it’s best to get advice from a doctor or physical therapist first.

If the ACL tear is treated conservatively (without surgery), the knee will recover a few weeks sooner. The rehabilitation goals and exercises are similar to those used after surgery. But you can start strength-building exercises earlier if you don't have surgery.

Depending on your individual situation and the extent of your knee injury, goals are set for each phase of rehabilitation and should be reached before starting the next phase. But the length of each rehabilitation phase varies from person to person. The phases can also overlap. The rehabilitation can be roughly divided into three phases:

The main goals of the first rehabilitation phase are to

• reduce swelling and inflammation in the knee joint,
• fully straighten the leg again and be able to easily bend it,
• control the thigh muscles, and
• be able to walk normally again.

In the first few days after surgery, you rest, cool and elevate (raise) the knee. Swelling is treated with lymphatic drainage massage, and pain is treated with anti-inflammatory painkillers. Gentle exercises to straighten and bend the leg are already started in the first week. Sometimes an electrical passive motion machine is used to move the leg. Important milestones include the following:

• Ideally, it should be possible to fully straighten your leg after 1 to 2 weeks.
• It is important to keep moving the kneecap to prevent adhesions (so it doesn't become "stuck") because that could cause problems later.

If it doesn't hurt, the thigh muscles can already be activated with isometric exercises in the first week after surgery. In these exercises, the muscles are contracted (tightened) without moving the knee joint – for example, by repeatedly raising and lowering the straightened leg while lying down. Sometimes, the muscles are also stimulated with neuromuscular electrical stimulation devices. But this hasn’t been proven to shorten the healing process.

Especially in the first 2 to 4 weeks, crutches should be used to take weight off the knee. Sometimes, people are advised to wear a knee brace that lets you straighten the leg but not fully bend it. But studies have shown that wearing the brace doesn't affect the overall treatment outcome. Some people feel safer with a brace, others find it annoying.

You then gradually add strengthening exercises that involve actively moving your muscles (dynamic exercises). After about 4 weeks, you can start doing exercises where your muscles have to work against resistance. It is important that you do the exercises the way your physical therapist shows you, being sure not to move the knee more than you should.

Neuromuscular training exercises can help to improve the stability and (subconscious) control of knee movements, which is useful in many everyday activities. An example of this kind of exercise is trying to keep your balance on a balance board.

Once you are able to bend your knee enough, you can start cycling a little on an exercise bike. This mobilizes the knee joint and warms up your muscles before exercises.

The second phase of rehabilitation starts when you have reached the goals of the first phase and can do the exercises properly without pain. At the end of the second phase, people can often start doing sports and more physically demanding activities again.

The aim of phase two is to further strengthen the leg muscles. The training involves more demanding exercises like lunges and one-legged squats. The knee is also moved more (increasing range of motion). To improve the maximum strength, the resistance is increased in some exercises. Neuromuscular training becomes more challenging too. In the last few weeks of this phase, sports-specific exercises can be added – like special jumping or running exercises.

The last phase of rehabilitation focuses on special strength, functional, and endurance training. The exact exercises will depend on your individual goals and problems.

It can take 12 months or more to reach the point where the tendon graft can fully take on the job of the missing ACL. To prevent new injuries, it is best to talk with your physical therapist before doing competitive sports again – and make sure the following criteria have been met:

• You have no knee pain or stability problems during training,
• you are able to do the sports-specific exercises correctly, and
• the difference in strength between the operated leg and healthy leg is less than 10%.

It is not possible to predict exactly when these criteria will be met.

Much of the information in this section describes the situation in Germany. The exact approach may be different in other countries.

In the first few weeks of rehabilitation, the knee can usually be easily treated in an outpatient physical therapy practice. Once the therapist has shown you how to do the exercises correctly, you can do many of them on your own at home. After the first few weeks, your doctor can prescribe treatment known as “medical training therapy” (Medizinische Trainingstherapie, or MTT) or “physical therapy with machines” (Krankengymnastik am Gerät, or KGG). With the help of exercise equipment, this allows you to do a wider range of exercises that are more tailored to your specific needs. Even afterwards, it can be a good idea to continue using exercise equipment over the long term, for example at a gym.

If your knee is very badly injured, you might have rehabilitation treatment in an inpatient setting. When done after surgery, this kind of inpatient follow-up treatment is called an Anschlussheilbehandlung in Germany. People who have inpatient rehabilitation treatment stay at a rehabilitation center for a few weeks.

Physical therapy is prescribed by a doctor. If the injury happened at work (if it was an occupational accident), extended outpatient physical therapy is also an option. Known as erweiterte ambulante Physiotherapie in German, this treatment can be prescribed by an accident insurance doctor. Which insurance pays and is responsible (your pension fund, health insurance or accident insurance provider) depends in part on whether the accident was an occupational accident and what insurance you have. The amount of rehabilitation treatment you have will also depend on what your doctors consider to be medically necessary.