In short

After every operation or serious injury, your body produces scar tissue. That is normal and needed for healing. Sometimes there is too much of it or it gets in the way, and a joint becomes stiff. The best approach is prevention: starting to move on time and in the right way, with physiotherapy. If the joint still stays stiff, your doctor can take further steps, and the earlier, the better the result.

What is scar tissue?

During an operation or injury, tissue is damaged. Your body repairs it through an inflammatory reaction that produces new connective tissue: scar tissue.

In some people this reaction is too strong. Too much tough connective tissue then forms in and around the joint, so it can no longer bend or straighten fully. This is called arthrofibrosis.[1][2] A special form after ACL surgery is the cyclops lesion: a nodule of scar tissue at the front of the knee that blocks full straightening.[3]

After which operations does it occur?

OperationHow often?
Knee replacement About 4% still have a stiff knee after 12 weeks (less than 90° of movement).[4]
ACL surgery About 4% need an extra procedure because the knee stays too stiff, down from 10% in the 1990s.[5] A cyclops that causes symptoms: in 2 to 11%.[3]
Rotator cuff (shoulder tendon) repair About 13% have a stiff shoulder after surgery, although this decreases after six months.[6]
Elbow, after a fracture or operation The elbow is very prone to stiffness.[7]

Who is at higher risk?

  • After a knee replacement: women and people who are overweight.[4]
  • After ACL surgery: a recent review of 48 studies lists these main risk factors:[5]
    • being female;
    • an ACL repaired acutely;
    • a meniscus repaired at the same time;
    • a knee that starts moving again too late after surgery;
    • a knee that does not yet have its full range of movement before surgery.

    Certain blood thinners and previous knee surgery also increase the risk.[8][9] A knee that is still inflamed before surgery gives a higher chance of a cyclops.[3] You can influence two of these risk factors yourself: make sure your knee already has its full range of movement before surgery, and start moving on time afterwards.
  • After shoulder surgery: older patients, people with diabetes, and those who had an extra procedure under the shoulder roof at the same time.[6]

Do you recognise this?

Every joint is stiff at first after surgery. The difference lies in how that stiffness evolves. The table below is based on how patients in our practices often describe it.

 Normal stiffness after surgeryStiffness from scar tissue
Where and why? In the joint itself. After the operation the joint is more sensitive in certain positions, and because of swelling, for example, you do not yet reach your full range of movement in the first weeks. After a few weeks, muscles can also become shortened, especially around the knee. Nothing is physically in the way. Scar tissue in or around the joint holds the movement back
Course Improves day by day and week by week Stays stuck in the same range of movement, even after weeks of exercise
While moving Eases and stays better Eases slowly when you move or warm up, but keeps coming back
How does it feel? Painful and swollen, but the joint "gives" Tough at the end of the movement. Not a hard block, but as if something sticky is holding it back
Getting in the way No Sometimes you can really feel something in the way, for example when scar tissue sits behind the kneecap tendon (patellar tendon)

Do you recognise the right-hand column, and has your range of movement stopped improving for several weeks? Discuss it with your physiotherapist.

When to see your doctor?

  • See your doctor or surgeon straight away if the joint is red, warm and painful and you have a fever. This may point to an infection.
  • Make an appointment with your surgeon if your range of movement has not improved for several weeks, despite good physiotherapy. Your physiotherapist measures your movement at every session and will contact your doctor in that case.

Prevention: moving on time and in the right way

The best treatment for stiffness after surgery is preventing it.[1][2][10]

  • Start early. After shoulder surgery, early exercise gave better movement and a three times lower chance of a stiff shoulder, compared with keeping the arm completely still in a sling for a while. Strong evidence¹ [11]
  • The right balance. In the first weeks your physiotherapist combines:
    • active exercises, to activate your muscles;
    • passive mobilisation, where the physiotherapist moves your joint as far as is safe.

    Too little movement leads to stiffness; too much too soon leads to more pain and swelling.
  • Keep swelling and pain under control. Pain and swelling switch your muscles down and make moving harder. Good pain relief, cooling and targeted exercises help your muscles work again.[10][12]
  • Daring to move. In practice we often notice that patients are afraid to move. That is understandable: after a knee replacement, about one in three people experience fear of movement.[13] It helps to know which sensations are normal, such as stretching pain at the end of the movement, and which are not. Then you dare to exercise enough, with confidence. Good explanation before surgery can reduce fear of movement. Limited evidence¹ [14]
  • Ready for surgery. For a planned operation, such as ACL surgery, it helps if your knee is calm and already has its full range of movement before the operation.[3][15]

Why is active exercise therapy so effective?

In active exercise you move yourself, with your own muscles. That does more than just having your joint moved:

  • Your muscles are switched back on. After surgery, your nervous system inhibits the muscles around the joint. Targeted exercises, together with cooling, have the best evidence for breaking through this inhibition.[12]
  • Your circulation gets going. Contracting muscles pump blood and fluid back to the heart. After leg surgery, simple ankle exercises improved the outflow of blood from the leg and reduced the risk of a blood clot.[16] This also helps to clear swelling.
  • You regain strength and movement. After a knee replacement, early physiotherapy with exercises improved pain, range of movement and quality of life.[17] A machine that moves the knee passively adds nothing to that.[18]

Passive mobilisation by your physiotherapist remains useful to regain your full range of movement, but always together with active exercises.

Read more about postoperative physiotherapy and about rehabilitation after an ACL injury.

Still stiff? The step-by-step plan

If physiotherapy alone is not enough, a step-by-step plan follows. First ask your physiotherapist for advice. They follow your movement week by week and can report back to the doctor who operated on you. Your physiotherapist's input is important here. Your doctor decides which step is needed. After every step you continue with physiotherapy straight away, to keep the movement you have gained.

Step 1. Adjusting the physiotherapy

Your physiotherapist adapts the treatment: more targeted mobilisation, exercises at the end of the range of movement and sometimes a splint that gradually brings the joint into the right position.[7]

Step 2. A corticosteroid injection

Corticosteroids ("cortisone") slow down inflammation and the production of new connective tissue. This makes scar tissue softer, so the tough stiffness feels more supple. That gives room to gain more movement with your physiotherapist.

  • For scars on the skin, a corticosteroid injection is one of the most used and effective treatments to make a thick, hard scar softer and flatter.[19]
  • For scar tissue in a joint, a recent review places the injection as a step after physiotherapy and before surgery.[20] The research is still limited: in knee replacements, an injection on top of manipulation under anaesthesia gave no extra gain, but it was safe.[21] Limited evidence¹

Step 3. Manipulation under anaesthesia

Under anaesthesia, the surgeon carefully moves your joint further than it can go on its own, so adhesions come loose.

  • After a knee replacement, the knee regained more than 90° of movement after such a manipulation in most studies.[22]
  • Acting on time pays off. People who had an early manipulation gained almost twice as much bending on average, with fewer complications, than those who waited longer.[23]
  • After ACL surgery, manipulation, possibly combined with step 4, is the most commonly used treatment for stiffness.[24]

Step 4. Surgical removal of scar tissue

Through keyhole surgery, the surgeon removes the scar tissue that is in the way (arthrolysis). In a cyclops lesion, the nodule is removed.[3]

  • After ACL surgery: in an American study, knee movement improved after such a procedure from 94° to 131° on average. The loss of straightening, 8° on average, disappeared completely. People treated within three months scored better on knee function afterwards.[25]
  • After a cyclops: of almost 200 people who had a cyclops removed, 92% would have the procedure again, with good knee function as a result.[26]
  • Smaller gains after ACL surgery: after ACL surgery it is often a matter of a few degrees of straightening or bending. After a knee replacement the loss is usually larger, and so is the gain: in those studies the knee gained 30 to 40° on average.[27][28]
  • The right moment: this procedure works best when it is not done too late, preferably within 3 to 6 months.[29][25]

Limited evidence¹ for steps 3 and 4: the studies mainly compare the situation before and after the procedure.

Popular treatments, but little evidence

TreatmentWhat does the research say?Label
Continuous passive motion (CPM) machine after a knee replacement This is a passive treatment: the machine moves your knee while your muscles do not work. On top of normal physiotherapy it gives no better movement, but a longer hospital stay and higher costs. See also "Why is active exercise therapy so effective?". No evidence¹ [18]
CPM machine after ACL surgery Can reduce some pain and swelling and help bending in the first weeks; the studies are of moderate quality. Limited evidence¹ [30]
Keeping the joint still for a long time "so it can heal" After shoulder surgery, long immobilisation gave more stiffness than early exercise. No evidence that it helps¹ [11]

"No evidence" does not mean something is harmful. If something feels good and is safe, you may use it, but it does not replace active rehabilitation.

What about the scar on your skin?

The scar on your skin can also become tough and hard. In studies, silicone gel or silicone sheets made a surgical scar flatter, more supple and less discoloured. Strong evidence¹ [31] Ask your physiotherapist or doctor when you can start.

At Magnus near you

At Magnus we have a lot of experience with rehabilitation after surgery and with stiffness from scar tissue, in Leuven (Naamsepoort), Kessel-Lo and Antwerp (Eilandje).

  • We measure your movement at every session, so we quickly see if your progress stalls.
  • We consult quickly within our team. If your rehabilitation is slower than expected, we discuss it with colleagues straight away and look for the best approach together.
  • We involve your surgeon on time. The earlier a next step is taken, the better the result.

Your physiotherapist for stiffness and scar tissue after surgery

Book with the gold “Make an appointment” button at the top right.

Kessel-Lo
Physiotherapist Thorin Kessel-LoThorin
Antwerp
Physiotherapist Lisa AntwerpLisa

Frequently asked questions

Is scar tissue after surgery normal?
Yes. Scar tissue is part of every recovery. It only becomes a problem when there is too much of it or it gets in the way, so your joint stays stiff.[1]

How soon after surgery should I start physiotherapy?
Ideally on the day of surgery itself or the day after, if your surgeon allows it. So book your first appointment before the operation. Moving early and in the right dose is the best protection against stiffness.[1][11][17]

Can scar tissue disappear on its own?
Scar tissue becomes more supple with time and movement. If your range of movement stays stuck for several weeks, it is time to talk to your doctor. The earlier treatment starts, the better the result.[23][29]

Does manipulation under anaesthesia hurt?
You are anaesthetised during the procedure. Afterwards the joint can be sensitive for a while. Continuing to exercise straight away is important to keep the movement you have gained.

Is my physiotherapy reimbursed?
Yes, with a referral. Rehabilitation after surgery often falls under the "Fa pathology" list, which means more sessions are reimbursed. Read more about reimbursement

Reviewed by Magnus Kinesitherapie. Last updated: 20 October 2026.

¹ What do the labels mean? Strong evidence: several good studies or reviews reach the same conclusion. Limited evidence: there are few or small studies, or the results contradict each other; it may help, but it is not certain. No evidence: good studies find no effect greater than a placebo, or there are no good studies yet. No evidence does not mean something is harmful. We base our information on reviews and guidelines published in 2019 or later.

This page gives general information and does not replace an examination by a doctor or physiotherapist.

Sources

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  3. Noailles T, et al. Incidence and risk factors for cyclops syndrome after anterior cruciate ligament reconstruction: a systematic literature review. Orthop Traumatol Surg Res. 2019. doi:10.1016/j.otsr.2019.07.007 (PMID 31405748) [review]
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