In December 2005 the KNEEguru community was invited to participate in an online survey on Return to activity after autologous chondrocyte implantation.

This survey was designed to provide an opportunity for KNEEguru bulletin board members to share their experiences of returning to sports and exercise activities after autologous chondrocyte implantation (ACI).

woman walks alond the beach enjoying her exercise regime

Over the last 10 years the vast majority of scientific studies on cartilage repair have based a 'successful' outcome on what the graft looks like from either an MRI scan or on second look arthroscopy or by what the new cartilage cells look like under the microscope. These are important factors, but just as important is whether having the ACI surgery helps the individual patient to return to the activities that they wanted to participate in.

The aim of this survey was to collate information about what activities ACI patients have or haven't returned to and why. This was a chance for ACI patients to provide their individual perspective on ACI surgery and rehabilitation and to help highlight areas that can be improved for ACI patients in the future.

Thanks to all of you who gave up your time to take part in the survey. The quality of your responses was exceptional.



There were 23 responses but 3 were excluded as it was less than 12 months after their ACI procedure. The average age was 34 years and the average time after ACI surgery was 29 months. An overview of the group is shown in the Table below.



FU = Follow Up, MFC = Medial Femoral Condyle, LFC = Lateral Femoral Condyle, MACI = Matrix-induced Autologous Chondrocyte Implantation, MACT = Matrix-associated Autologous Chondrocyte Implantation


Why choose to have ACI surgery?

One of the first questions in the survey was 'why did you choose to have ACI surgery?' and the main reasons that you gave for choosing to have ACI surgery in the first place were interesting:

  • Lack of choice or limited options (47% of respondents)
  • Sports/exercise activities (35% of respondents)
  • Pain and/or other symptoms (29% of respondents)
  • Surgeon recommendation (18% of respondents)
  • To avoid/delay having a knee replacement (18% of respondents)

Almost half of you felt that either your options were restricted by things including the size of the cartilage damage; your age; prior knee surgery; or that you weren't given any other surgical options other than ACI.

Over a third of you said that sports and exercise activity was a key factor in why you decided to opt for ACI surgery in the first place. You wanted to return to an active life that ranged from taking part in competitive sports to playing with the children. The interesting point here is that more of you cited return to sports and exercise than cited pain and/or other symptoms such as swelling, locking or giving way as the main reason for your choice to have ACI.

However, there was a huge range in your responses with some individuals who were only going through the ACI surgery to be able to play sports to other individuals who quite openly stated that they never intended to go back to playing sports again and just wanted to be pain free.


How did you rate your outcome?

The Brittberg Rating is a scale that was developed in 1990s to measure clinical outcome after cartilage repair surgery. If we take a look at how you rated your ACI outcome based on the Brittberg rating 59% of you reported excellent or good results as you can see in the pie chart below.

chart of brittberg rating

Previous studies have reported excellent and good outcomes for 55-90% of patients so the results from this survey are at the lower end of this range. It is not possible to say why this is the case from the survey but there are a couple of potential reasons. Firstly, the ratings weren't by the surgeon they were by you, the patient, and they were supplied anonymously so perhaps some of you were more honest in your answers. Secondly, the KNEEguru community isn't representative of the general population as there are proportionally more people who have poor knee surgery results or continuing problems in the community and therefore it would be expected that outcomes results would be lower.


What activities did you return to?

Despite the fact that almost half of you (41%) rated your outcome as 'fair' or 'poor' in actual fact only 18% of you didn't return to sport at all. This is positive as it shows that even if your clinical outcome isn't as good as you may have hoped it shouldn't necessarily stop you from taking part in sports and exercise activities altogether.

However, only 18% of you made a full return to your original sport or exercise activity. Two-thirds of you found that you had to either return to your original activity with limitations or that you had to switch to a different sport/exercise activity.

brittberg pie chart

The most common change of sporting activity was to switch from a high impact activity such as football, basketball, running or baseball to a lower impact sport such as cycling, walking and golf. For those of you who didn't change sports and exercise activities many of you found ways to compensate for limitations due to your knee problems including:

  • Reducing how often you take part in that sport or exercise activity.
  • Lowering the level at which you play.
  • Allowing more time for your knee to recover between sessions.
  • Increasing the amount of strengthening work at home or at the gym.

In terms of the reasons for returning or not returning to your main sport or exercise activity there were a few schools of thought. Some of you returned to sports and exercise activities despite still experiencing symptoms. Whilst others with minimal symptoms took a different perspective on things and chose not to return to your main activity as you thought that it may cause more damage to your knee joint over the long term.

There was also a general feeling that ACI rehabilitation takes a lot of effort, both mentally and physically, and that you didn't want to risk having to go through it all again and/or weren't prepared to put your families and friends through it again.


How well informed were you?

Rehabilitation after articular cartilage repair is quite different to a lot of other surgical procedures. The researcher therefore felt that it was important to find out how well informed patients thought they were before they had their ACI surgery about the rehabilitation process. The results of how well you thought you were informed are shown in the graph below.

informed graph

Almost half of you felt that they were fully informed about the rehabilitation for ACI before you had the surgery.

However, the other half of the group felt you received some information but that you were generally not very well informed.

Would you opt for ACI surgery again?

If we now look at whether people would opt for ACI surgery again 76% of you said yes you would, 23% no and 6% were unsure.

What was interesting was that those people who said that they wouldn't opt for ACI surgery again tended to be the ones who considered that they weren't very well informed about the rehabilitation for ACI. It is not possible to draw any direct conclusions from this trend but it may suggest that informed patients tend to be more satisfied with their treatment than those people or were under or ill informed about ACI rehabilitation.


How can ACI rehabilitation be improved?

When you were asked how ACI rehabilitation could be improved you identified five key areas:

  • Psychological preparation & support (59% of respondents)
  • Knowledge/education (47% of respondents)
  • Communication (29% of respondents)
  • Rehabilitation programmes (29% of respondents)
  • Muscle strengthening (24% of respondents)

Over half of you felt that there was a need for better psychological preparation and support including pre-operative counseling, confidence building and the medical profession adopting a more holistic approach with patients.


Just under half of you thought that enhancing knowledge and education would improve the experience.

Interestingly the knowledge and education enhancement was predominantly focused on physiotherapists with a number of you stating that your physiotherapist had either never heard of ACI or knew nothing about the procedure.

Linking in with the previous area was the need for improved communication between the surgeon and physiotherapist as well as between the surgeon and the patient.

You expressed a general need for clearer, more structured rehabilitation guidelines that could be personalised to your own individual needs and goals.

Muscle strengthening was one of the components of the rehabilitation programme that was specifically highlighted for improvement. It was felt that there should be a greater emphasis on muscle strengthening in the ACI rehabilitation programme especially preoperatively.


Advice from ACI Patients

The ACI patients who took part in this survey had the following advice for anyone considering ACI surgery -

  • Read as much information as you can.
  • Find a physiotherapist prior to your surgery who can work with you long term.
  • Ask about the potential complications of ACI surgery.
  • Start looking at local gym facilities prior to your operation.
  • Try to get in the best shape possible before your operation.
  • Be realistic about your expectations.
  • Realise that rehabilitation is slow - be prepared for a long recovery.
  • Make sure you are attached to a physiotherapist who knows what ACI is.
  • Choose a surgeon who has a good track record in ACI surgery.
  • Understand what you are getting yourself into.


Final Thoughts


man playing tennis

ACI rehabilitation is long and demanding, both physically and mentally. Individuals choose to undergo ACI surgery for a range of reasons but many want to, and do, return to an active lifestyle.

ACI rehabilitation is a process, a journey. You may start off the journey with full intentions of returning to your main sport or exercise activity but at the end of the journey you may have changed your mind, possibly more than once as you react to the experience.

Anyone reading this article must bear in mind that the survey was of a small sample of 20 KNEEguru bulletin board members and that the KNEEguru community is not representative of the general population. It is therefore not possible to apply the results of this study directly to the general population.

Finally it is worth remembering that despite some of the issues regarding ACI rehabilitation that this survey has raised and the variance in individual expectations three-quarters of the people who took part in this survey said that they would opt for ACI surgery again.

The results from this survey were presented at the following conference in January 2006:

Hambly, K. Cartilage repair rehabilitation: The human factor. Paper presented at: 6th International Cartilage Repair Society Congress, 2006; San Diego, USA.

A larger prospective study looking at return to sports and exercise activities following ACI is being planned using the information gained from this KNEEguru survey.