One undesirable outcome of knee surgery can be arthrofibrosis, also known as “stiff knee syndrome.” The condition sometimes occurs in joints that have recently been injured or undergone surgery. Over time, scar tissue builds up inside the knee, causing  the knee joint begins to shrink and tighten.

Scar tissue from arthrofibrosis can severely impact the necessary range of motion of the knee and, in the most severe instances, result in a permanent inability to bend and straighten the knee.

The likelihood of developing arthrofibrosis increases with the severity of the trauma to the knee joint or the length of a surgery. Essentially, the longer the knee is immobilized, the greater the risk of the condition occurring. This is why it is important to keep the knee moving, and another reason why your surgeon may prescribe that you use of a CPM machine while lying in bed and recouping from surgery. Your surgeon or physical therapist (PT) may also provide exercises designed to reduce the risk of developing arthrofibrosis. There’s also evidence that a compression dressing, cryotherapy (the application of extreme cold), and a suction drain may reduce the odds of experiencing arthrofibrosis.

Recognizing Anthrofibrosis

It is important to keep in mind that the incidence of arthrofibrosis is extremely low. It occurs in only about 1 percent of cases. Not surprisingly, some stiffness is normal following a total knee replacement (TKR). In addition, slight stiffness may persist for months or years and become more apparent after exercise or activity. However, if arthrofibrosis occurs, certain symptoms are common. These include:

A Flexed Knee Gait

Your gait (i.e., the cadence and form by which you walk) can indicate the health of your knee alignment and motion. Walking with a bent knee can be a sign of stiffness and may indicate that you are developing arthrofibrosis.

Worsening Pain in the Knee

Normally, pain steadily decreases after surgery. If you experience an uptick in pain consult with your doctor. It could be the result of arthrofibrosis, especially when it is accompanied by reduced flexibility.

Ongoing Swelling

Arthrofibrosis causes swelling in the soft tissue around the knee but this is different than swelling due to fluid buildup. Your doctor can determine the cause of the swelling and steps to treat it.

Weak Quadriceps

If you are unable to contract your quadriceps muscle in the front of your leg or have other issues moving your leg get checked for arthrofibrosis.

Hotness Around the Knee

It is normal after surgery to feel that your knee is warm or hot. However, if “hotness” feeling remains after 2 or 3 weeks, contact your physician.


If your surgeon diagnoses you with arthrofibrosis, you will require additional treatment or surgery. Common treatments include:


In some cases, the surgeon will manipulate the knee in order to break up scar tissue while you’re under sedation or anesthesia.

Arthroscopic Surgery

In addition, a growing number of surgeons are now turning to minimally invasive arthroscopic surgery to remove the scar tissue. This process is called arthrolysis.

Open Surgery

In the worst cases, more aggressive surgery may be required. After treatment or surgery you will require physical therapy.

After the initial treatment for arthrofibrosis is complete, there are numerous rehabilitation activities designed to maintain motion and/or prevent a recurrence of the condition: 

  • use of CPM machine
  • exercise like walking on a treadmill, cycling, and immersion in water
  • bracing 

Although rare, it’s important to be on alert for arthrofibrosis. Those who experience the condition are likely to encounter serious hurdles on the path to recovery and a more active lifestyle. Monitor your range of motion throughout your recovery and consult with your doctor if you notice stiffness or any decline in the function of your artificial joint.