Description, Causes and Risk Factors:

Arthrofibrosis is an inflammatory condition that leads to the production of an excessive scar tissue in or around major joints. Arthrofibrosis can be caused by the initial injury to the joint or from surgical complications. Infections and bleeding into the joint are believed to be major causes or contributing factors involved in the disease.

Arthrofibrosis is one of the major complications of ACL surgery and is one of the most difficult to treat. Whatever the cause, the excess scar tissue limits range of motion ("ROM") and functionality. The condition can be quite painful and debilitating.


In general, the likelihood of developing arthrofibrosis increases with the severity of a knee joint injury, the extensiveness of related surgery, and the length of time that the knee is subsequently immobilized. However, not everyone who sustains a major knee injury or who undergoes major surgery will develop arthrofibrosis. Some people are more prone to developing this problem than others. Genetic factors apparently predispose some patients to develop arthrofibrosis by way of an inherited tendency to form hypertrophic (excessive) internal joint scar tissue in response to injury and/or surgery. Such individuals often heal surgical ligament repairs and grafts quite solidly, but go on to heal "excessively," forming an overabundance of unwanted fibrous scar in their knee. This essentially makes their knee too stable, to the point of being stiff and lacking proper joint motion. Such "heavy scar-formers" can literally fill up their entire knee joint cavity with thick, tough scar tissue. This obliterates all of the normal open spaces within the joint, adhering everything together and effectively "freezing" the joint (hence the traditional term "frozen joint").

Patients with "sensitive" knees or low pain thresholds are also more likely to develop this problem, as they find it more difficult than most to use and move their knee after injury or surgery. Lack of joint motion and use leads the knee to form more abundant and less compliant scar tissue than it otherwise would, and allows the relatively unused (and thus unstretched) surrounding knee capsule to contract down and tighten up, almost like "shrink-wrap" does. A stiff, arthrofibrotic knee is a very difficult problem for the Orthopedic surgeon & physical therapist to handle. It usually requires a specially planned, intensive protocol of surgical treatment and post-operative management.


Symptoms include joint stiffness, pain, redness, heat, swelling, crepitus, and lack of ROM (range of motion).


A thorough History & physical examination are paramount in evaluating a patient with arthrofibrosis. The goalis to elicit the cause of the arthrofibrosis. Limitations toextension are generally secondary to pathology in theintercondylar notch region. Limitations of knee flexionare generally secondary to scar development within themedial and/or lateral gutters or within the suprapatellarpouch region.It is also important if the patient hashad previous operative intervention to obtain the operative reports. This will potentially aid in understanding thecause of arthrofibrosis (i.e., timing of surgery, multipleligament reconstruction), associated pathology (cartilagelesions, MCL injury), and technical considerations thata routine patient may not completely understand and convey to the physician. In a patient who has signi?cant pain,consider infection and/or CRPS (complex regional pain syndrome) as a contributing causeof knee stiffness. Diagnostic imaging is required andhelpful in evaluation of these patients. Standard protocol begins with standard weight-bearing anteroposteriormerchant, long-leg alignment, and bilateral 30 degree lateralviews to assess for patella baja. X-rays & MRI scans may provide extra information in dif?cult cases.


The traditional treatment approach for arthrofibrotic knees that did not loosen up with aggressive stretching and exercise in physical therapy has been to place the patient under anesthesia and then literally break up and tear the restrictive, internal scar tissue within the joint by forcing the knee to fully bend and straighten. The surgeon accomplishes this by way of strenuous, manual joint manipulation. The procedure therefore came to be known as a manipulation under anesthesia, or "M.U.A.", and is still in common use. In cases of severely frozen knees, extremely stressful manipulation forces may be required to break up the scar tissue and get the joint moving again. This poses a risk to a patient who has not been able to bear much weight on their leg for quite some time, because the femur and tibia may have lost a considerable amount of bone mineral (calcium phosphate), thus weakening them. This increases the chance of an inadvertent femoral or tibial fracture occurring at the time of the joint manipulation. The preference over the years has been to perform an arthroscopic, internal surgical scar resection to remove as much restrictive scar tissue as possible, prior to manipulating the knee. This approach not only leaves very little scar within the joint to re-organize and solidify once again, but it also reduces the manipulation force required to get the knee moving, thus reducing (but not eliminating) the chance of femoral or tibial fracture.

NOTE: The above information is educational purpose. The information provided herein should not be used during any medical emergency or for the diagnosis or treatment of any medical condition.

DISCLAIMER: This information should not substitute for seeking responsible, professional medical care.


  1. Alvin Clark

    In addition to MUA and arthroscopic arthrolysis, sometimes open arthrolysis is performed. Also, for arthrofibrosis following knee replacement, revision knee replacement a treatment option for cases that did not respond to MUA, arthroscopic arthrolysis and open arthrolysis.

    • maisteri

      Thank you for your comment and the additional information.


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