Arthrofibrosis (from Greek: arthro- joint, fibrosis - scar tissue formation) has been described in most joints like knee, hip, ankle, foot joints, shoulder, elbow, wrist, hand joints as well as spinal vertebrae. In the knee, it can happen after knee injury or surgery. There is excessive scar tissue formation within the joint and surrounding soft tissues leading to painful restriction of joint motion that persists despite physical therapy and rehabilitation. The scar tissue can involve only a part of the knee joint or the whole knee. The scar tissue may be located inside the knee joint or may involve the soft tissue structures around the knee joint. Arthrofibrosis may arise without an obvious cause or it may follow a known cause.
Arthrofibrosis of the knee (Frozen Knee)
Arthrofibrosis of the knee, also called as "Frozen Knee", has been one of the more studied joints as a result of its frequency of occurrence. Arthrofibrosis can follow knee injury and knee surgeries like arthroscopic knee surgery or knee replacement. Scar tissues can cause structures of the knee to become contracted, restricting normal motion. Depending on the site of scarring, knee cap mobility and/or joint range of motion (i.e. flexion, extension, or both) may be affected. Symptoms experienced as a result of arthrofibrosis of the knee include stiffness, pain, limping, heat, swelling, crepitus, and/or weakness. Clinical diagnosis may also include the use of magnetic resonance imaging (or MRI) to visualize the knee compartments affected. The consequent pain may lead to the cascade of quadriceps weakness, patellar tendon shortening and scarring in the tissues around the knee cap—with an end stage of permanent patella infera—where the knee cap is pulled down into an abnormal position where it becomes vulnerable to joint surface damage.
Arthrofibrosis after knee injury, knee arthroscopy or other surgeries
The first step in treating arthrofibrosis is appropriately directed physical therapy. There are several potential treatments for arthrofibrosis. Treatment varies on the cause and duration of the fibrosis. Often physical therapy is used as an attempt at conservative management. If physical therapy fails options include: manipulation under anaesthesia (MUA), arthroscopic lysis of adhesions, open lysis of adhesions, or in the case of long standing fibrosis in the setting of knee arthroplasty (knee replacement) a revision open surgery may be needed.
Arthrofibrosis after knee replacement
Arthrofibrosis can occur after total knee replacement or partial knee replacement. The common pathway for the development of arthrofibrosis (AF) is excessive collagen fibril deposition in and around the knee. This can be accompanied by shortening of the patellar tendon (patella baja/infera) which can also contribute to limited flexion. The rates of AF after TKA vary widely in the literature as there is no standard definition. One study's definition is a total range of motion (ROM) <90 degrees constitutes AF, another definition is flexion contracture >10 degrees, or inability to flex the knee >100 degrees. AF is a diagnosis of exclusion; before making a final diagnosis of arthrofibrosis, other causes of stiffness following knee replacement should be excluded (ex: infection, malposition of the implants, or mechanical block to motion).
In the case of AF after total knee arthroplasty (TKA) management typically consists of attempt at aggressive physical therapy, and in the case that fails manipulation under anesthesia (MUA). The rates of MUA after TKA vary widely. There are several reasons for this: there is no definite consensus to when a MUA is required (different surgeons follow different indications), there is no standardized definition of arthrofibrosis (see above), and depending on how and when it is performed MUA is not always a reliable treatment. For these reasons treatment patterns vary widely. Successful MUA depends on many variables. MUA after TKA has been found to be most successful if performed in the first 8-12 weeks after surgery. After 12 weeks manipulation is much less likely to have an acceptable outcome.
If the fibrosis is chronic (more than 12 weeks) there is a decreased likelihood of success with MUA and an increased chance of success with open lysis of adhesions or revision surgery, however this carries with it the attendant risks of another open procedure (i.e., infection, blood clots, blood loss, etc).
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