One way of looking at the process of rehabilitation is through the kinds of questions that patients ask after having the surgery. They usually ask four specific questions, and looking in turn at the typical answers to those questions will help you to understand the rehabilitation process.

When is full-weight bearing allowed?

In other words: When I can throw away my crutches? One way of looking at this question is to describe it as a kind of traffic light. This traffic light is red, and it becomes green when you are able to match certain criteria.

The criteria are not strictly time-dependent, because there are so many different surgical procedures that a patient can have, and so many different kinds of patients, and different tissues, etc. We therefore cannot say that this stage lasts for two weeks, three weeks, or five weeks…

The surgeon will indicate the approximate time it will take to reach this first traffic light. However, the criteria for the first traffic light are:

1. Orthopaedic surgeon approval. In other words, the orthopaedic surgeon should tell you that you can get rid of your crutches.
2. Extension (straightening) of the knee to the same degree as the contralateral (other) limb. This is very important, as too many patients without perfect extension try to have a normal gait. This is impossible, and instead of walking they limp, which is bad for the joint and limb. It is very important to have full and complete extension, as in the contralateral limb, first.
3. The absence of swelling and pain. If the knee is swollen, it is better to avoid weight bearing. Preoperatively, the surgeon may estimate that, after 30 days, you may be able to walk without crutches. However after that time-frame, you still have a swollen knee, you will have to wait.
4. Recovery of the correct gait cycle; i.e, the pattern of movements during walking.

To reach the goal of walking without crutches, you must follow the rehabilitation with progressive exercises. Connected with this type of issue, the exercises should include range of motion exercises, which help achieve full extension, as well as exercises that help to decrease the swelling in the knee and exercises that helps you regain a normal gait pattern.

When may I run on a treadmill?

Running is a question everybody asks about, not only athletes. Most people who have this kind of surgery are young, and need at least to run after a bus, or run with their children, etc. Running is something that they all want to achieve.

In order to run, there are certain criteria, which make up the second traffic light:

1. You can attempt to run when you have no pain while walking. If you still have any pain while walking, it is impossible to run, so don’t even try.
2. Active knee flexion (bending) of the knee over 120º. This is very important because, when you walk, it is important to have full extension, but when you run, you must be able to bend your knee. It is important to do range of motion exercises to have this kind of freedom in the knee.
3. Appropriate muscle strength in the thigh and in the leg. In order to run, you need strength.
4. You surgeon advises you that the cartilage procedure is mature and successful enough to consider advancing to this high force activity.

In the first rehabilitation period, as discussed above, the most important exercises are range of motion exercise. In this second recovery period, strengthening exercises are important, because you need the strength in your muscles to be able to run.

When may I run on a field?

When a patient can run on a field, what it really means is that they can run by themselves. The second traffic light is running on a treadmill, which is under the control of the rehabilitation team, whereas this is running outside.

The criteria are connected to strength:

1. At least 90% of strength compared to the contralateral knee muscle. If your muscle is, for example, 100% in the right leg and you had surgery on the left leg, the left side should have at least 90% of the strength in the right leg.
2. The patient can run on the treadmill at 8 km/h for 10 minutes without any discomfort and pain.

If you reach these criteria, you can start on-field rehabilitation with an athletic trainer. There is a progressive set of exercises that one can do on the field.

When can I play sport again?

This last question is asked if the patient is an athlete or if they like to play sport. Nowadays, many patients ask about this after cartilage injury, because they would like to have surgery so that they can play sport again.

It is not easy to say to someone that they cannot do sport again, as a lot of patients would like to do so. This is the last traffic light, and there are four criteria:

1. Surgeon approval. Depending on the kind of surgery, the surgeon has to agree to you returning to sport.
2. No strength deficit between the two legs, in terms of the quadriceps and hamstring muscles. It is very important that the operated knee has 100% strength.
3. There must also be complete range of motion, with no pain and no swelling.
4. There must also be full recovery of endurance capacity. To measure this, we do aerobic and anaerobic threshold tests, and the patient must be able to cope with fatigue without any problems. This is because fatigue could be a source for a re-injury, so it’s very important to have a complete endurance recovery.

You must successfully complete a sport specific functional progression program, which gradually (in a protective environment) duplicates all the functions and stresses of the sport on a level-by-level progression. If you have pain or swelling during this functional progression, you will need to stop at the level below these symptoms occurred and then continue at that level with more rehabilitation prior to proceeding to the next level. Once all levels are met without pain, swelling or instability, you are ready to return gradually to sport under your athletic trainer’s watchful eyes.

For each of the four questions listed above, there is an expectation of the average time they take. What is important to understand is that, for each patient, the time will not be the same. It depends on so many different aspects that it is difficult to say that it will take 1 month, 3 months, 6 months, 9 months or even 12 months.

This is why it is very important to understand the individual criteria for each traffic light. The average for the first traffic light is maybe 1 or 2 months while, for the second traffic light, it is maybe 3, 4 months. For the third traffic light, it is maybe 6–9 months and for the last one, it is 1 year.

However, this can change depending on the patient, and there is not one rule for everybody. There is a range of time for everybody, but it depends on the individual patient’s capacity to meet the criteria and to get the okay from the surgeon, depending on the type of surgery that was performed.

If there are no contraindications or complications, the patient may be fully functional once they have completed rehabilitation. Unfortunately, with some large or extensive preoperative damage, the patient’s and surgeon’s goals is a pain free normal life without sport. It is important to discuss this with your surgeon and therapist before surgery and continue the conversation during the rehabilitation process.