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What Causes Knee Scar Tissue?

By E.A. Sanker
Updated Mar 03, 2024
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Knee scar tissue develops as a result of traumatic injury to the knee or as a complication of knee surgery. It might form after procedures such as anterior cruciate ligament (ACL) surgery or total knee replacement. Like other types of scar tissue, scar tissue in the knee is a bundling of collagen fibers that develops during wound repair. The formation of scar tissue is often problematic because of its association with knee stiffness. During the healing process, some individuals develop a condition known as arthrofibrosis, in which excessive internal scar tissue is formed, causing the ligaments surrounding the joint cavity to tighten and restricting or fully preventing the bending of the knee.

The formation of excess knee scar tissue depends on the severity of the trauma and on genetic factors. In arthrofibrosis, open spaces within the joint are filled with stiff fibrous tissue, and the patient experiences a lack of motion, or a "frozen" joint. The lack of mobility in the knee further exacerbates the problem and results in the formation of stiffer scar tissue than would otherwise be present, restricting motion even more.

In cases where excessive joint stiffness is observed because of knee scar tissue, further surgical intervention might be required to return the knee to an acceptable range of motion. Six weeks after a total knee replacement, the patient is expected to be able to bend the knee at least past 90 degrees. If this is not the case, and if physical therapy has failed to produce the desired results, the patient might be returned to the hospital to undergo a process in which the knee is forcibly bent in order to break the scar tissue and restore motion. This procedure typically is conducted under general anesthesia and is known as manipulation under anesthesia (MUA). After the scar tissue has been broken through MUA, the patient must undergo more physical therapy.

While this intervention is sometimes necessary, orthopedic surgeons and practitioners of sports medicine usually recommend pursuing a conservative course of treatment when possible. The use of a continuous passive motion (CPM) machine is prescribed following knee surgery to prevent the formation of stiffness and scar tissue in the knee. The CPM works by gently bending the knee in a series of repetitions, extending the knee's range of motion without the need for physical exertion that could damage the knee. Physical therapy and deep tissue massage are also popular therapeutic methods used to improve flexibility and break down knee scar tissue.

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Discussion Comments
By anon998623 — On Jul 17, 2017

I had TKR surgery on 04/05/2017. Two days later when I would bend my knee it felt like something rubbing in my knee and it makes a popping noise. I told the PH and the doctor about it and the doctor said it was scar tissue and that he had removed a lot of scar tissue during surgery. My ROM after six weeks of PH and doing the exercises that were recommended I had a ROM of 150. I went back to the Dr. on 07/14/2017 because of the rubbing and again he told me it was scar tissue and the only way to get rid of it was surgery and that it may come back again. My range of motion has decreased to 125 which he said was really very good. My question is, can scar tissue form in two days. and if a second surgery is done what are the chances of the same thing happening?

By anon972927 — On Oct 07, 2014

The use of a CPM machine must be applied immediately after surgery. The first 72 hours are the most critical. Constant cpm Motion is a must. CPM machines that rotate from -10 to +140 are the best. After the first 72 hours the machine is somewhat useless, except for comfort, because it will lessen the pain. If not applied immediately after surgery, then you are wasting your time. Scar tissue will heal about 90 percent in the first 72 hours.

By anon929366 — On Jan 31, 2014

I had bilateral TKR in November 2011. My PT seemed successful and I was progressing as expected. Then in April my knees got sore. The surgeon said it was referred pain from my back, which I did not believe. He said the artificial joints looked great.

A second orthopedist blamed my arthritic hips for the knee pain. A couple other doctors didn't have an opinion.

Finally, well over two years after surgery with chronic pain, another doctor said the cause of pain is calcified tendons and scar tissue. It feels like there are tight knots inside my knees, and is difficult to walk or stand. Grocery shopping takes major effort because of pain, stiffness and weakness. I can bend my knees, but they hurt all the time.

I am going to have shots to deaden the nerves in my knees and hope for the best. It is terrible to endure difficult surgery and then have more pain.

By anon336758 — On May 31, 2013

I had a total knee replacement in October 2012. I had a lot of scar tissue and didn't have ROM so I had a manipulation in November. It got worse.

Three months after the manipulation, I had arthroscopic surgery to cut the scar tissue. Within eight days of the surgery, and being on a CPM and going to PT, I lost over 35 degrees of motion. In addition, my extension is at -7. At this point, is my only option a revision? I'm reading these comments and it doesn't look like anyone had success. Please let me know your experiences and if I have any other options.

By anon331135 — On Apr 21, 2013

I was bone to bone. I had an initial knee replacement, used the immobilizer walker and cane. After a month of painful PT being able to bend slightly and using the CPM machine. The volume of scar tissue would not allow me to go no further than 5 to 10 degrees. So, I had a manipulation, and when there was no improvement, I had arthroscopic surgery.

When the doctor saw there was too much scar tissue for the arthroscopic surgery, he performed a knee revision. The knee revision was a bust because the volume of scar tissue that amassed while I was healing still would not allow me an improved ROM. I continued with PT and other forms of rehab measures and massage therapy. The massage therapy did give me some relief as the swelling went down tremendously and my left leg became stronger than my right leg. Twelve months passed then my left leg was going numb, tingling sensations, paining when I would place my leg a particular way and it was sometimes painful.

I did research and found another surgeon. An X-ray revealed the first surgeon put the device in crooked. So I let the new surgeon give me a second revision. He is responsible for the slight improvement of my leg because I can bend my knee about 45 degrees. I do have a lot of scar tissue and it is an everyday process to control it. I had the second surgery in January 2011 and if I press just below my knee, I can feel the scar tissue is not hard. If I press on it, it leaves an impression then becomes smooth again. I do have a limp, but not as severe as it was before the second surgery.

Every day, I must exercise my knee. Scar tissue is alive. When I work out, my leg swells and after I am done, the scar tissue shows me it is ticked off by tightening the area above and below my knee. It chokes the heck out of my leg. Scar tissue has a mind of its own. So, I have decided to live with it. I do not want to go through any more trauma on my left leg.

My issue is how to deal with the compensation of my right leg because I know that in the long term, it will affect my mobility. So, other than pool therapy and massage therapy, what other things can I do to improve the quality of my mobility?

By anon325303 — On Mar 15, 2013

I had total knee replacement in 2010, and it wasn't working. Then they tried manipulation and still could not get it going along with physical therapy. The doctor said he was going back in to see what the problem was.

When I woke up in the hospital for the second time, I was told the doctor took the whole thing out and put in a better knee. Anyway, I went through the same procedure at physical therapy and had to go through manipulation again without success. I was then sent to Stanford in Redwood City, Ca. for re-constructive surgery and the doctor told me, "I see patients like you every day. I can guarantee you will have at least 60 percent bend so you will be able to walk without a limp." Of course, I said let's go for it. This was done 2011. I went back to physical therapy and no progress once again.

He also tried another manipulation and if I have 10-15 percent, bend I am lucky. The reconstructive surgery left me worse off. I was at the point of no pain after the first two, but with this one I continue to have pain which I have just had to learn to deal with.

Are there any procedures left for me? I try to keep up hope and figure someday, someone is going to do something about the frozen knee after replacement.

By anon258373 — On Apr 01, 2012

I had ACL surgery Nov 2011. It resulted in loss of extension (-10 degrees) and flexion only to 90 degrees. I underwent an MUA procedure March 2012 where they got my knee to -5 degrees extension and 140 degrees flexion. After 48 hours of constant CPM (no toilet liberties) we took the machine off and guess what? I have extension at -10 degrees and flexion at 90 degrees -- and a whole lot of discomfort.

What are my next options? I am a gymnast and need to return to my sport. The flexion doesn't bother me as much as the loss of extension.

By anon175821 — On May 13, 2011

if CPM fails what is next step if any? I had this treatment still unable to bend my knee.

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