Stiffness After Knee Replacement Surgery

Risks, Causes, and Current Treatment Options

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A knee replacement surgery is performed to replace the worn-out cartilage of the knee joint. Knee replacement is an excellent procedure for severe knee arthritis. Unfortunately, complications can occur after a knee replacement, even when all goes well at the time of surgery.

One possible complication of a knee replacement is stiffness after the surgery has been performed. People with a stiff knee after knee replacement may experience an inability to fully straighten the leg, to bend the knee, or both.

This article explains what problems can occur after knee replacement surgery. It also discusses possible treatments for knee stiffness after you have this type of procedure.

Therapist working on a patient's knee

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Assessing Risk Before Surgery

When trying to predict the likelihood of stiffness after a knee replacement, the most important thing to consider is how well you can move your knee before having surgery. People who have stiff knees heading into knee replacement surgery usually have stiffer knees after the operation.

Those who can easily move the knee before having surgery are less likely to have stiffness after surgery.

There are steps that can be taken at the time of surgery to help release tight ligaments and tissues around the joint. These methods can also help remove any damaged pieces of cartilage or bone that are interfering with movement. But sometimes the flexibility of the tissues is limited to a point that cannot be fully corrected.

Expected Range of Motion

After knee replacement surgery, it is important to work with a physical therapist to restore as much range of motion as possible. Typically, the range of motion will progress quickly during the first three months. It can continue to increase for up to two years following surgery.

Normal motion after knee replacement is defined as the ability to get within 5 degrees of a straight knee and the ability to bend the knee back to 90 degrees. Most knee replacements have movement ranging from zero degrees to 110 degrees or more.

The range of motion of the replaced knee can be improved with a combination of stretches, exercises, and gradual resumption of normal activities. Some surgeons will recommend the use of a machine to bend the knee, called a CPM (continuous passive motion).

Causes of Stiffness

In some people, knee motion can be difficult to regain after surgery. Lack of normal motion after knee replacement can be due to one of the several causes, or a combination of causes. Lack of normal motion may be caused by:

  • Inadequate pain control
  • Poor motion before surgery
  • Excessive scar formation
  • Improper positioning of the implants
  • Other surgical complications

Inadequate Pain Control

Pain control after joint replacement is usually a manageable problem. But in some people, this can be quite difficult. Some patients find the side effects of pain medication impossible to tolerate. But a lack of adequate pain control can lead to difficulty increasing the motion of the newly replaced joint.

It is important to partner with your doctor to develop a pain treatment plan that works for you.

Poor Motion Before Surgery

Your motion before surgery can be used to predict your motion after surgery. Patients with stiffness before their surgical procedure are more likely to have stiffness after surgery.

Excessive Scar Formation

Some people seem to make more scar tissue than others. And there are some situations where you experience more scar formation. People who are more likely to have stiffness after surgery include:

  • Patients who have undergone joint surgery before
  • Patients who are having revision knee replacement surgery, a repeat knee replacement after the previous one fails

Improper Positioning of the Implants

Surgeons make an effort to balance the knee at the time of surgery. This means finding the proper size and alignment of the knee replacement so that the knee joint is not too tight and not too loose. The goal is to make this balancing the same whether the knee is straight or bent.

This is precisely why a knee replacement is a difficult procedure. In fact, the art of perfecting this takes many years. Errors in the positioning of an implant may not be apparent on the operating table. They may only become noticeable when the patient is slow to recover from surgery.

Other Surgical Complications

Complications of surgery often lead to other problems. Patients who experience joint replacement infections, complex regional pain syndrome, or other complications have a higher chance of developing stiffness.

Treatment

Treatment of stiffness after knee replacement depends on how long it's been since surgery and the cause of the stiffness. The usual treatments for stiffness are:

Aggressive Physical Therapy

Physical therapy is a useful treatment for a stiff knee, especially within the first three months after knee replacement. Physical therapy can also be considered after this time, but the results are not as good as early physical therapy.

A new type of splint called a dynamic splint has also shown some encouraging results when used in conjunction with physical therapy.

Manipulation Under Anesthesia

A manipulation is a procedure where no incisions are made. The patient is given anesthesia, usually through an IV. While you are sleeping, your surgeon forcibly moves the knee to break up scar tissue. This procedure is most beneficial in the six to 12 weeks after surgery.

The primary concern with a manipulation is the risk of bone breakage. This is a real issue because most patients who have a manipulation treatment are older and at greater risk of osteoporosis. Breakage is also more likely if the manipulation is performed more than a year after the replacement.

Surgical Removal of Scar Tissue

Surgical removal of scar tissue after knee replacement is seldom performed but may be helpful in some rare circumstances. The results of removing scar tissue have not been particularly good at improving motion. Doctors usually consider other treatments first.​

Revision Knee Replacement

When all other options fail or the knee replacement parts are not positioned well and can't be repositioned, it may be necessary to perform a revision knee replacement. The bone cuts and the size of the new replacement can be modified to help allow for better knee motion.

Determining the proper treatment of a stiff knee after replacement depends on the cause of the stiffness and the length of time since your replacement. Your doctor can make recommendations for your knee based on your specific situation.

Summary

Surgeons perform a knee replacement surgery to repair a worn-out knee joint causing severe arthritis. Even if a surgery is successful, you can still end up with complications. Knee stiffness is a complication that may occur.

Treatment options include aggressive physical therapy, manipulation under anesthesia, surgical removal of scar tissue, and revision knee replacement. Your surgeon will decide which treatment is best for your unique needs.

A Word From Verywell

Stiffness after knee replacement surgery can generally be avoided with appropriate pain control, physical therapy, and steps to reduce the likelihood of complications. However, in situations where stiffness occurs, there are steps that can be performed to try to improve the situation.

Early treatment of knee stiffness after surgery is extremely important. Delayed treatment (of six months or more) is far less likely to have good results. In cases like these, repeat surgery may be the only option.

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4 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
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