What Are the Causes of Stiffness After Total Knee Replacement?

Stiffness following knee replacement surgery can be caused by a variety of factors.
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A total knee replacement, also known as knee arthroplasty, can feel like a second chance at life after years of dealing with a sore, arthritic knee. While most people achieve improved range of motion and better all-around function after a knee replacement, this isn't always the outcome. Unfortunately, some patients still experience a stiff knee after surgery. Understanding the causes of stiffness can help you address the issue and ultimately be successful in your rehab after this operation.



Stiffness after a knee replacement can occur because of a number of issues, including infection, hardware complication or excess scar formation (called arthrofibrosis).

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What Is Knee Stiffness?

There are several different ways to define stiffness, including the overall degree of bend after knee replacement surgery. Patients with knee range of motion that lacks at least 5 degrees of straightening (called knee extension) or who can't bend their knees (called knee flexion) past 100 degrees are considered to have post-operative fibrosis, which causes stiffness.


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In addition, anyone with knee range of motion that is less than it was prior to surgery or who is generally dissatisfied with resulting post-operative motion, may also fall into this category.

Read more: What Exercise Should I Do to Stop the Noise in My Knee Replacement?

What Are the Causes?

Several different things may cause stiffness after a knee replacement. Hardware component failure or incorrect surgical placement can limit range of motion in some cases.


In addition, post-surgical infection or the growth of excessive bone around the surgical site (called heterotopic ossification) can also impact your movement. Infrequently, the development of complex regional pain syndrome (CRPS), a condition that causes swelling, pain, and stiffness after a trauma or surgery, is to blame.

Most commonly, however, post-surgical stiffness occurs as a result of excessive scar tissue developing after your surgery. Called arthrofibrosis, this fibrous scarring develops within the joint itself and can limit your range of motion and impede your ability to perform your day-to-day tasks. In addition, excessive scarring can lead to pain that persists long after your surgery.


Who’s at Risk of Arthrofibrosis?

There are several different risk factors for developing a stiff knee after surgery. Individuals with decreased range of motion prior to surgery have a greater risk of arthrofibrosis after their operation.

African Americans and patients who are under the age of 45 are also about twice as likely to need surgery to correct their stiffness (called a manipulation). Smokers are at a greater risk too.


Read more: What Are the Symptoms of a Failing Knee Replacement?


Getting Your Motion Back

The reason behind the limitation in your knee's motion will help determine how to go about getting your movement back. If your range-of-motion limitations are caused by infection, hardware issues, heterotopic ossification or CRPS, immediate intervention by your physician may be required as these are more serious in nature.


In the case of tightness caused by arthrofibrosis, however, there are several steps you can take.

Start With Stretching

Immediately following your discharge from the hospital, it's important to start a home stretching routine. Regularly performing exercises that work on your range of motion will improve your overall flexibility and knee movement. Try the following exercises to improve the motion in your knee joint.


Stretch Your Hamstrings

The hamstrings sit in the back of your thigh and attach just below your knee joint. Tightness in these muscles can limit your ability to extend or straighten your leg, but stretching the back of the knee helps.

HOW TO DO IT: Sit straight up on the edge of a chair with your leg extended in front of you. Without rounding your spine or bending your knee, lean forward at the hips until you feel a stretch behind your leg. Hold this for 30 seconds and perform five per day.


Read more: The Best Exercises to Increase Range of Motion After Total Knee Replacement

Work on Knee Flexion

Stretching the muscles and tissues in the front of the thigh can help improve the bend or flexion in your knee joint.


HOW TO DO IT: While seated in a chair with your leg hanging off the edge, begin by slowly kicking the knee backward. When you're unable to bend it any more, hook your good leg on top of the surgical one and use it to bend it further until a light to moderate stretch is felt in the thigh or knee. Hold this for 10 seconds and do 10 to 15 repetitions each day.

Read more: How to Increase Flexion After Total Knee Replacement

Increase Knee Flexion With IASTM

If traditional treatments like stretching haven't been helpful in relieving your stiffness, a specialized form of massage may address your arthrofibrosis. IASTM, short for "instrument-assisted soft tissue massage," uses metal tools to massage the areas around the knee and can break up the scar tissue that forms and impedes motion.

A 2016 study published in the Journal of Knee Surgery found good improvements in knee flexion among patients who underwent Astym therapy (a form of IASTM) after developing a post-surgical stiff knee. Talk to your physical therapist about making it part of your rehab.

Use Knee Splints

Adding a static knee splint to your daily routine may also help you combat arthrofibrosis. These devices lock the knee into a low-level stretch for a longer period of time and can effectively increase the joint's range of motion.

Typically, this is done in 15- to 30-minute increments and the splint is worn up to three times per day. Your physician will be able to help you obtain a splint if he feels it's appropriate.

Consider Surgical Manipulation

If more conservative measures fail to improve your knee stiffness, the next step may be a surgical manipulation. During this procedure, you're put under anesthesia and the surgeon bends your knee enough to break through the scars that have formed.

While this type of intervention is typically done up to three months after a knee replacement, a 2017 study in Knee Surgery, Sports Traumatology, Arthroscopy found that it most effectively improves knee range of motion when it's done within 12 weeks of the initial knee replacement surgery.

Warnings and Precautions

While the steps listed can be helpful in regaining your knee motion, certain post-operative symptoms should not be overlooked. Progressively worsening pain or stiffness, fever, swelling, redness around the knee or night sweats should be immediately reported to your surgeon. Any of these issues could be a sign of infection within your knee joint.

Read more: Remedies for a Swelling Knee After Knee Surgery




Is this an emergency? If you are experiencing serious medical symptoms, please see the National Library of Medicine’s list of signs you need emergency medical attention or call 911.

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