You are here

What triggers arthrofibrosis? (part 4 of course on arthrofibrosis)

Inflammation and limitation of knee motion is normal in the early days after surgery. However, when the normal sequence of events turns into an abnormal arthrofibrosis reaction, the surgeon and therapist must be able to immediately identify that something is going wrong, as there is only a small window of opportunity to resolve this problem.

Normal healing response after joint injury or surgery

Following surgery or injury, the body sets off what is termed an 'inflammatory cascade' - a process that it uses to fight infection and protect itself. This involves the production of cytokines - the whole family of chemical mediators which can mediate the response of the white blood cells, growth factors, and TGF-beta products ('transforming growth factors') which control scarring.

  • redness
  • swelling (oedema)
  • heat
  • pain
  • reduced function

This inflammatory response usually becomes quiescent at approximately 2-4 weeks after surgery. The body needs to go through this whole predictable process in order to heal and rebuild. Because this response occurs in all patients, the surgeon and therapist need to have a well-defined postoperative protocol. During the first month after surgery, this should include the classical RICE concept of rest, ice, compression, elevation, and as well, exercises to regain normal knee motion and muscle function.

In cases of arthrofibrosis, the same initial sequence occurs, but it then becomes an unpredictable and exaggerated cascade which is destructive rather than constructive, leading to considerable tissue damage and scarring.


inside the knee joint


On left - view down the arthroscope of a normal knee, showing the rounded end of the femur (condyle), the flattened top of the tibia, and the meniscus wedged between them.


scar tissue inside knee

On right - similar view in a knee with advanced arthrofibrosis, showing a dense growth of fibrous scar tissue and overgrown synovium obscuring the normal anatomy.




Abnormal healing response in arthrofibrosis

In my experience, approximately 10% of patients have an exaggerated inflammatory response where, at 2 to 3 weeks postoperative, they are not regaining knee motion as I normally expect. These patients require special treatment which, when initiated this early after surgery, will be successful. I always stress that treatment for a knee motion problem must be initiated within these first few weeks to prevent a permanent loss of flexion or extension (ref 1).

I have found that 1% of patients do not respond to treatment. These patients represent very difficult cases and have what surgeons refer to as primary arthrofibrosis. Occasionally, these patients will have had prior surgery performed elsewhere where they experienced exactly the same problem - a genetically-based exaggerated inflammatory response which will always be a problem for them. Incidentally, in our study on 443 consecutive ACL reconstructions (ref 1), we found that females were not more prone to knee motion problems than males - there was no gender difference.

So, to sum up - 89% are going to do well, 10% are going to have a problem that you can address, and 1% are going to have residual problems requiring major knee surgery. Note, I am talking major knee surgery.

Some conditions are more commonly associated with the developent of arthrofibrosis -

  • Infection - The surgeon must always exclude infection - infection is the number one cause of arthrofibrosis - I repeat - THE number one cause. When a knee is not responding in a normal manner and scar tissue has formed, infection must be suspected until proven otherwise.

    Infection comes in acute case where it is obvious; the knee is drained and surgery performed immediately. There are also sub-acute cases where the joint shows very little (if any) swelling - but scar tissue has developed and the joint is warm.

    Commonly, there will be chemical abnormalities that can be measured in the blood. However, in some instances all cultures are negative and it becomes a dilemma as to how to treat the patient. In these cases, we use infectious disease consultants to administer empiric large doses of antibiotics because we suspect an infection (as the joint is red and there may be a mild temperature elevation), even though we were not able to culture a specific bacteria.

  • Haemarthrosis (bleeding into the joint) - There are different types of haemarthrosis which may occur after surgery - one is mild which has approximately 25 cc in the joint - this does not require draining.

    A moderate haemarthrosis - 50 cc in the joint - definitely requires draining because it will shut down the quadriceps and hamstrings - patients may lose 30-40% of their strength. Severe haemarthrosis also requires draining as the knee joint is very tense and painful.

  • After long periods of immobilisation in a cast - Orthopaedic surgeons sometimes have to immobilise the knee after surgery, but today this is kept to a minimum. However, a major problem is that the knee may have been immobilised for several weeks after injury before the surgeon first sees the patient.

  • After fractures around the knee joint/high tibial osteotomy - Of course, immobilisation is likely to be part of the necessary management after a fracture. While we use immediate knee motion following high tibial osteotomy, some surgeons may still use a cast postoperatively.

  • Post ACL surgery - It is a clinical decision when to perform ACL reconstruction without risking triggering arthrofibrosis. Before reconstruction, we follow these steps to avoid the development of a postoperative knee motion problem. The patient should regain full motion unless a mechanical block exists (such as a meniscus tear), swelling and pain from the injury should be resolved, and most importantly, a strong muscle contraction should be demonstrated. I think that if you ask, 90% of the surgeons would state that this requires at least 4-6 weeks. There are special patients who have minimal swelling and good return of muscle function within 1-2 weeks of their ACL rupture. Some surgeons will say (correctly) that these cases do not pose special problems because they have fulfilled all the preoperative goals. It is a clinical decision for the surgeon to determine that these goals have been met and decide that surgery is now safe for the patient. The other factor which is particularly important is the surgical technique itself. A poorly positioned graft may cause mechanical problems and also trigger arthrofibrosis.
  • Post arthroplasty - Stiffness after arthroplasty may be due to a number of factors besides arthrofibrosis. Pre-op flexion, for example, is an established predictor of poor post-op ROM due to stiffness of the extensor mechanism. When arthrofibrosis does develop, the patient may notice a 'clunk' due to the development of a fibrotic band stretching from the top of the patella to the femur.

  • Patellofemoral joint surgery and other procedures altering the extensor mechanism.


1 Frank R. Noyes, Sandra Berrios-Torres, Sue D. Barber-Westin, Timothy P. Heckmann. Prevention of permanent arthrofibrosis after anterior cruciate ligament reconstruction alone or combined with associated procedures: a prospective study in 443 knees. Knee Surg, Sports Traumatol, Arthrosc (2000) 8 : 196-206

Updated: 22 Apr, 2013

Dr Frank R Noyes

Knee Surgeon

Based at the Cincinnati Sportsmedicine and Orthopaedic Center in the USA, Dr Frank Noyes is one of the world's most prominent figures when it comes to knee surgery. A prolific researcher and writer, he has published over 200 studies and articles in the world's top orthopaedic journals and...

0 Comment(s) to the "What triggers arthrofibrosis? (part 4 of course on arthrofibrosis)"




  • Latest
  • Blogs
  • Popular
  • Tags
The concepts surrounding the knee meniscus are not difficult to understand, but they are not always...
Friday, November 14, 2014 - 7:21pm
Because the patella is an integral part of the whole muscle-tendon-bone structure that extends the...
Saturday, September 13, 2014 - 5:57pm
This is a clinical test for laxity of the anterior cruciate ligament. The patient lies on his/her b...
Saturday, September 13, 2014 - 10:44am
Fifty years ago, Dr. Hughston, one of the founding fathers of American Sports Medicine, imparted a...
Wednesday, August 20, 2014 - 11:51pm
Hello I really wanted to add my story to the site!  I have read many helpful stories about knee surgeries...
Friday, December 5, 2014 - 1:45am
So after completely tearing the anterior cruciate ligament of my left knee, I underwent ACL Reconstruction...
Sunday, November 16, 2014 - 8:08am
Hi my name is Samantha and this is my MPFL story so far.My left knee has been dislocating from the age of 8...
Thursday, October 9, 2014 - 11:40pm
9 days until surgery and i am not nervous at all, which makes me wonder because i have anxiety. Over the...
Wednesday, October 1, 2014 - 4:46pm
This phase is immediately after injury or surgery. Focus is on: wound management protecting the lim...
Wednesday, March 26, 2008 - 7:32pm
The back of the knee is called the 'popliteal' region of the knee. The depression in the middle of...
Sunday, June 29, 2008 - 9:43am
Exercise bikes, static bikes, stationary cycles, bicycle ergometers - these are all names for the b...
Thursday, March 20, 2008 - 3:04pm
All the well-recognised exercises and stretches for full knee rehabilitation, with photographs and...
Wednesday, March 26, 2008 - 7:38pm
-A A +A

Word of the Day

A stem cell is an unspecialised cell with a remarkable ability to divide over and over and become differentiated into another type of cell, replacing damaged body tissue.

User login