Arthrofibrosis is a joint that heals too well. After surgery or an injury, scar tissue keeps building inside and around the joint until it stiffens.1PubMed Central. Arthrofibrosis Nightmares – Prevention & Management Strategies It is best known as a complication of knee replacement and ACL reconstruction, though shoulders, elbows and hips can be affected too.2PubMed Central. Arthrofibrosis and large joint scarring3PubMed Central. Arthrofibrosis and large joint scarring
It is not simply a lack of effort at physical therapy. The body’s own healing response is overreacting. Most people can win back a good deal of movement, and the treatments range from gentle home stretching to keyhole surgery.
What Arthrofibrosis Is and Who Gets It
Doctors describe arthrofibrosis as an exaggerated immune response to an injury or operation that lays down scar tissue around a joint and makes it stiff.4PubMed Central. Arthrofibrosis Nightmares – Prevention & Management Strategies What it takes away is range of motion, meaning how far the knee bends and straightens. Ordinary stiffness after knee surgery is mostly swelling, and it usually eases week by week with therapy. With arthrofibrosis, progress stalls or even reverses despite steady work.
In weeks 4 to 12 after surgery, a stalled recovery has a recognizable look. Your bend measurement stops improving at therapy visits, or slips backward. The knee feels tight and blocked rather than just sore. Straightening it fully gets hard, so walking feels uneven. These patterns are what usually prompt a surgeon to name arthrofibrosis.
A stiff knee early on does not by itself mean arthrofibrosis. In the first weeks, stiffness is often driven by swelling and muscle guarding, and it loosens as the swelling goes down. Surgeons generally prefer to use the label only after a knee has stayed stuck despite a reasonable stretch of good therapy, because it depends on the pattern over time rather than a single measurement. Other things can also limit bend, such as a poorly positioned implant, infection, or a pain-driven reluctance to move. That is why a stiff knee gets examined before the scar is blamed. Scarring is driven by your biology, not laziness, and some people who work very hard still develop it.
The name combines “arthro” (joint) and “fibrosis” (scarring), so it literally means scarring of a joint. Hearing it does not mean the joint is damaged beyond repair. The scar is mostly soft, tight tissue inside and around the joint, not new bone, which is part of why treatment aimed at loosening it can work.
Why Scar Tissue Takes Over the Joint
Any surgery or injury inflames the tissue, and local immune cells release chemical signals.5IAA. Myofibroblasts Those signals turn ordinary repair cells into scar-making cells that act very differently.6IAA. Myofibroblasts They pour out collagen scar, contract strongly and glue tissues together into adhesions.7IAA. Myofibroblasts Low oxygen in the wounded tissue and signals from immune cells keep feeding the process, which can keep it running.8PubMed Central. Pathological mechanisms and therapeutic outlooks for arthrofibrosis
An adhesion is a band of scar that glues together two surfaces that should slide freely past each other, such as the tendon, fat pad and bone around the kneecap. Where surfaces are stuck, the knee cannot glide. Bending pulls against the glued spot and produces a tight, blocked feeling at a particular point in the movement.
In ordinary healing, scar-making cells do their job and then fade away as the wound closes, so the tissue settles into a stable repair. After knee replacement, healing can become stuck instead, so the scar cells stay active and the joint lining shrinks.9PubMed. Pathophysiology of Arthrofibrosis After Total Knee Arthroplasty: Current Concepts and Future Directions They appear to keep building scar after they should have stopped. That is why the problem can get worse over weeks even though the surgical wound looks fine from the outside.
The capsule around the knee is like a stretchy sleeve. Scar thickens and shortens that sleeve, and a shrunken sleeve physically blocks bending and straightening. This is why force alone often cannot stretch it out. The new scar collagen is also laid down in a disorganized way, which makes it stiff rather than flexible.10PubMed Central. Arthrofibrosis and large joint scarring Scar cells from these knees behave much like those in Dupuytren’s contracture, the condition that pulls fingers into the palm.11PubMed Central. Human Outgrowth Knee Fibroblasts from Patients Undergoing Total Knee Arthroplasty Exhibit a Unique Gene Expression Profile and Undergo Myofibroblastogenesis upon TGFβ1 Stimulation
Who Is at Higher Risk
After knee replacement, younger patients and those whose knee was already stiff before surgery are more likely to develop it.12PubMed. Epidemiology and Risk Factors for Arthrofibrosis Following Total Knee Arthroplasty: Toward Effective Prevention Younger people tend to have a more vigorous healing response, so the same surgery can trigger more scar than it would in an older patient. Genes and individual biology may make some people prone to it.13PubMed. Epidemiology and Risk Factors for Arthrofibrosis Following Total Knee Arthroplasty: Toward Effective Prevention A replacement part placed slightly out of position raises the risk too.14PubMed. Epidemiology and Risk Factors for Arthrofibrosis Following Total Knee Arthroplasty: Toward Effective Prevention Full knee replacements are revised for scarring more often than partial ones, possibly because the larger operation and moving the kneecap cause more scar.15PubMed Central. Factors associated with arthrofibrosis-related revision following 14,325 total or unicompartmental knee arthro-plasties: an analysis from the Dutch Arthroplasty Registry
A knee that already bends poorly before a replacement starts with less motion to protect, so any scarring costs a larger share of what is left. Surgeons often look at pre-operative bend as one clue to how recovery may go, though it is only one factor among several and does not decide the outcome.
After ACL reconstruction, scar can form a ball at the front of the new ligament, called a cyclops lesion, which blocks straightening. A swollen or stiff knee at the time of surgery, a narrow notch in the thigh bone, a tunnel drilled too far forward and tight hamstrings raise the risk.16PubMed Central. Cyclops Lesions of the Knee: A Narrative Review of the Literature Having surgery within 8 days versus 6 weeks after injury made no difference in one study.17PubMed Central. Cyclops Lesions of the Knee: A Narrative Review of the Literature
Age, genetics and bone shape are fixed. Getting motion back before surgery is something you can work on, and asking your surgeon about your stiffness risk is reasonable.
Symptoms and Complications
The main symptom is a knee that won’t bend or straighten as far as it should.18PubMed Central. Arthrofibrosis Nightmares – Prevention & Management Strategies Pain, warmth and swelling often persist longer than expected. In severe cases, even walking can be hard for years.19PubMed Central. The Prognosis of Arthrofibroses: Prevalence, Clinical Shortcomings, and Future Prospects
Lost motion shows up in daily tasks. Climbing stairs normally takes a good amount of bend, so with less motion they become one step at a time. Getting out of low chairs or cars turns awkward. A knee that won’t fully straighten makes you limp and tires the thigh. Aching can disrupt sleep.
Scar in the fat pad below the kneecap can tether it and pull it down, a problem called patella baja.20Radsource. Arthrofibrosis of the Knee A low-riding kneecap causes front-of-knee pain, trouble fully straightening by muscle power and less motion.21PubMed Central. Intraarticular arthrofibrosis of the knee alters patellofemoral contact biomechanics Left untreated, it can cause arthritis behind the kneecap.22Radsource. Arthrofibrosis of the Knee Because kneecap scarring can damage cartilage, a few signs deserve prompt review: a kneecap that seems to move less or sit lower, motion getting worse from week to week, or pain that rises despite rest.
How Doctors Diagnose It
Diagnosis rests mainly on the doctor’s exam and measuring your bend.23Radsource. Arthrofibrosis of the Knee An MRI shows how much scar there is and rules out problems that look similar.24Radsource. Arthrofibrosis of the Knee
At the appointment, the doctor uses a hinged ruler to measure the angles. They compare your bend and straightening to the other knee. X-rays check implant position and kneecap height, and blood tests may check for infection. It helps to bring your therapy records of motion over time, notes on when progress stalled, and a list of pain medicines and what helps.
Ruling out other causes comes first because infection can look like arthrofibrosis. Both cause a hot, swollen, stiff, painful knee, and the treatments are very different, so infection has to be excluded before scar removal is considered. A loose or poorly positioned implant can also limit motion and cause pain, and it is treated by correcting the implant rather than by stretching. This is why the diagnosis can feel slow: the answer comes from combining the exam, imaging and sometimes lab results.
Treatment Without Surgery
Therapy aims to loosen soft tissue and the joint while lowering pain.25PubMed Central. Multimodal conservative management of arthrofibrosis after total knee arthroplasty compared to manipulation under anesthesia: a feasibility study with retrospective cohort comparison Forceful techniques that raise pain can increase inflammation and scarring.26PubMed Central. Multimodal conservative management of arthrofibrosis after total knee arthroplasty compared to manipulation under anesthesia: a feasibility study with retrospective cohort comparison
A good session leaves stretch discomfort that fades. Pain lasting into the night suggests it may have been too much. Ice and pacing help keep swelling down, and your therapist needs to hear if pain rises. A therapist who backs off and one who pushes hard can both be following good practice; what matters is how your knee responds. If it is hotter, more swollen and less mobile the day after a session, that session was likely too aggressive.
Home stretching devices hold the knee at a gentle stretch for long periods, so the tissue lengthens gradually rather than being yanked in a short session. You typically use one at home several times a day, increasing the stretch as you tolerate it. Among over 11,000 people, high-intensity home stretch devices raised average bend from about 80 to 108 degrees.27PubMed Central. Efficacy of non-operative treatment of patients with knee arthrofibrosis using high-intensity home mechanical therapy: a retrospective review of 11,000+ patients Most gains came within 2 months, and many avoided more surgery regardless of age or sex.28PubMed Central. Efficacy of non-operative treatment of patients with knee arthrofibrosis using high-intensity home mechanical therapy: a retrospective review of 11,000+ patients
In manipulation under anesthesia, the surgeon bends the knee while you are asleep to break scar. Because your muscles are relaxed, the knee can go further than you could manage awake. Most people gain motion and have less pain afterward.29OrthoInfo. Manipulation Under Anesthesia After Knee Replacement Continued stiffness is the most common problem, while fracture and lasting pain are very rare.30OrthoInfo. Manipulation Under Anesthesia After Knee Replacement The benefit tends to fade unless you begin therapy right away, since the scar can tighten again if the new range goes unused. Expect soreness and swelling for a while, and plan good pain control so you can keep moving. Anti-inflammatory and anti-scar drugs are being tested on scar cells, but none is yet a proven fix.31PubMed Central. The effect of anti-inflammatory and antifibrotic agents on fibroblasts obtained from arthrofibrotic tissue
Surgery to Remove Scar Tissue
Arthroscopic lysis of adhesions is keyhole surgery that cleans out scar, followed by gentle manipulation and immediate rehab.32PubMed. Arthroscopic Lysis of Adhesions for the Management of Arthrofibrosis Following Total Knee Arthroplasty It is used when non-surgical treatment has failed.33PubMed Central. Outcomes of Arthroscopic Lysis of Adhesions for the Treatment of Postoperative Knee Arthrofibrosis: A Systematic Review The surgeon makes a few small incisions, passes a camera and thin instruments into the joint, and cuts or shaves away the bands of scar blocking movement. Once the scar is cleared, the knee is gently bent to confirm the new range. It is usually done as a day case or with a short stay, which is part of its appeal compared with a larger operation.
On average, motion improved from about 81 to 123 degrees.34PubMed Central. Outcomes of Arthroscopic Lysis of Adhesions for the Treatment of Postoperative Knee Arthrofibrosis: A Systematic Review Gains usually range from about 20 to 60 degrees, with less pain and better function.35PubMed. Arthroscopic Lysis of Adhesions for the Management of Arthrofibrosis Following Total Knee Arthroplasty It doesn’t always restore a perfect knee, but it often makes stairs and chairs manageable.
Physical therapy, sometimes with a motion machine, starts right away to hold the new range.36PubMed Central. Arthroscopic Lysis of Adhesions for the Stiff Total Knee Arthroplasty The early weeks are especially important for keeping the gains. Severe cases may need open surgery or revision.
Useful questions for your surgeon: What motion do you expect for me? Will I have a motion machine? How will pain be managed? What if the scar returns?
Living With It and Long-Term Outlook
Depending on the joint and severity, limits can last years or indefinitely.37PubMed Central. The Prognosis of Arthrofibroses: Prevalence, Clinical Shortcomings, and Future Prospects In severe cases, people have lost jobs because they couldn’t do basic tasks.38OSF Preprints. Pathophysiology of Arthrofibrosis of the Knee after Ligamentous Injury and Repair: Synthesizing Past and Current Knowledge for Personalized Prevention Still, many people see steady improvement over months, especially once the right treatment starts. Progress can come in plateaus, with little change for a while and then gains, so a flat few weeks does not necessarily mean you have stopped improving. Some people end up with a knee that works well enough for daily life but still does not bend as it once did.
People describe an overwhelming loss of function and identity, with harm to social life and mental health.39PubMed. “My bloody leg” – The lived experience of arthrofibrosis after total knee arthroplasty Getting support for mood is part of treatment, so tell your doctor or therapist about low mood or anxiety.
A few practical steps help. If progress stalls, ask for a referral to a knee stiffness specialist. Ask about workplace adjustments, consider counseling or peer groups, and track small gains to stay motivated.