Arthrofibrosis of the knee is a condition whereby knee motion is limited due to scar tissue, contractures after injury or surgery, or due to the effects of osteoarthritis over time. There are 2 types of motion that we usually think of as being important to assess arthrofibrosis. First, a lack of an ability to straighten one’s knee out is a flexion contracture. Flexion contractures of more than 7 or 8 degrees compared to the opposite normal limb have been shown to limit patient’s function, lead to early arthritis and can cause secondary issues, such as pain or muscle weakness, with the same-sided hip or sacroiliac joint due to limping. This is because a joint with a flexion contracture effectively has a shorter limb. The other type of condition that we think about with arthrofibrosis of the knee is an inability to fully flex one’s knee. People need about 110-115 degrees of flexion to function with most activities of daily living. This includes being able to sit effectively in a car or bus, to be able to arise comfortably off a chair, and to be able to perform a full revolution on a stationary bike.
The workup for arthrofibrosis of the knee requires a full history and physical. It is important to determine the onset of the stiffness, associated injuries or conditions, and the previous treatments to address the issue. X-rays of that side are necessary to determine multiple things including evidence of extra bone healing, joint subluxation or abnormalities of position of the patellofemoral joint. One would also look for evidence of osteoarthritis to include joint space narrowing and bone spurs.
The treatment for arthrofibrosis varies from observation, the use of bracing, physical therapy, and surgery. Observation alone is rarely performed, but may be recommended in some patients. Dynamic splinting for either extension or flexion deficits may also be indicated in some patients. This may be especially true in patients who have just had surgery or an injury and for whom these splints may be effective at improving motion due to the early timing after surgery or injury.
Surgical treatment for arthrofibrosis depends upon the specific pathology. In almost all circumstances, the surgery would be much less successful with a failure to follow specific rehabilitation principles. This can include the use of extension dynamic splints, a CPM machine and/or a very closely monitored physical therapy regimen.
In patients with osteoarthritis, the removal of bone spurs which are limiting motion can be very effective at returning knee motion back to normal or near normal levels. However, these surgeries are often found to be unsuccessful if one does not follow specific rehabilitation guidelines. In our practice, we have patients start physical therapy the first day after surgery with two 2-hour sessions daily for 1-2 weeks and then daily physical therapy until the knee quiets down over the course of the next few weeks. Most patients need to focus almost exclusively on maintenance of the knee motion gained in therapy for the first 6 weeks after their surgery. In our practice, we found this to be very successful in improving patients function and motion.
In patients who have developed arthrofibrosis after an injury or surgery, one needs to make sure that the timing of surgery is correct such that one does not cause injury to a damaged ligament or healing fracture or a surgical repair or reconstruction. In most circumstances, we would wait a minimum of 3-4 months before proceeding with a surgery to treat arthrofibrosis.
Patients who have a flexion contracture after surgery usually need a cleaning out of scar tissue and need to be carefully assessed for a possible arthroscopic posterior capsular release. These patients are then monitored very closely postoperatively and most patients would use an extension dynamic splint to help maintain their knee extension for 6 weeks or longer after surgery. In patients who do not have full flexion, which is usually after a more severe knee injury or very large surgery, a cleaning out of scar tissue of the suprapatellar pouch and scar along the medial or lateral gutters of the knee is often required. Postoperatively, patients are almost uniformly allowed full motion and full weightbearing of their knee, with most patients requiring the use of a continuous passive motion machine to help decrease the chance of recurrence of scar tissue.
Arthrofibrosis surgery can be very complex. It is important to have a very thorough assessment ahead of time to look at all the different causes of the joint stiffness. Complications can include intraoperative fractures from weak bones, ligament tears, especially from ligaments that may not have been surgical reconstructed in the ideal anatomic position, and recurrent stiffness. Since we do not know why patients form arthrofibrosis in all circumstances, there may be a genetic predisposition to it that we do not have the ability to recognize presently. Thus, even in the best of circumstances, some patients may develop a stiff knee again after surgery. However, when one follows the basic principles of releasing scar tissue, regaining motion, and then working with therapists after surgery, the chance of recurrent scarring is 10% or less.
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