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Osteoarthritis is the most common form of arthritis and can cause joints to feel stiff and painful. It is more common in older people, but can also occur in younger people, especially if there has been injury to a joint. Sometimes osteoarthritis causes the joints to swell and change shape, and sometimes the joints make grinding or creaking noises.
The symptoms of osteoarthritis can vary quite a bit. Sometimes there is no pain at all and sometimes the pain can be severe and it is difficult to move the joints. Sometimes pain with osteoarthritis is accompanied by swelling and localized heat and in other cases it is much less. There may be muscle loss around the joints, making them feel weaker. Almost all joints can develop osteoarthritis. The most common sites are the fingers, thumbs, knees and hip, as well as the lower back and neck.
Osteoarthritis is a complex process involving several chemical processes taking place in the joint and in the body. Not all of these processes are equally well understood. We are gaining more and more knowledge about the treatment and cause of osteoarthritis so that newer and newer treatment methods are coming on the market and joint replacement surgery can be postponed.
Osteoarthritis (also called osteoarthritis ) is a chronic joint disorder in which the cartilage in a joint slowly wears down. It is the most common form of rheumatoid arthritis and primarily affects joints such as the knees, hips, hands and spine. With osteoarthritis, not only the cartilage changes, but also the underlying bone, joint capsule and surrounding muscles and tendons.
Below is a comprehensive list in which cause and effect are not always obvious
Wear and tear of cartilage:
Cartilage is the smooth, elastic tissue that protects the ends of bones and reduces friction. In osteoarthritis, this cartilage becomes thinner, brittle and rough, allowing bones to rub against each other.
Inflammation and swelling:
The joint capsule and mucous membrane (synovium) can become inflamed(synovitis), causing pain and stiffness.
Bone changes:
The body often forms extra bone (osteophytes or “parrot jaws”) at the edges of the joint, which can restrict movement.
The bone under the cartilage becomes harder and thicker(subchondral sclerosis).
Reduced joint fluid:
The quality of the synovial fluid (which “lubricates” the joint) deteriorates, increasing friction.
Pain: Especially with movement or strain (e.g., climbing stairs, lifting).
Morning stiffness: Brief stiffness after rest (usually <30 minutes).
Cracking sound(crepitations): When moving the joint.
Swelling: Due to inflammation or fluid accumulation.
Reduced mobility: Difficulty bending, stretching or walking.
Age: Occurs more often in people older than 45 years.
Obesity: Extra stress on joints (especially knees and hips).
Previous injuries: E.g., a torn meniscus or ligament injury in the knee.
Overuse: Due to heavy work, sports or incorrect postures.
Genetic predisposition: Family members with osteoarthritis increase the risk.
Gender: Women are more likely to have osteoarthritis than men.
Osteoarthritis = “wear and tear” (usually localized in 1-2 joints).
Rheumatoid arthritis = autoimmune disease (inflammation in multiple joints).
Gout = acute inflammation caused by uric acid crystals.
Physical examination: Assessment of pain, swelling and mobility.
X-rays: Shows bone changes and narrowing of the joint gap.
MRI: Shows details of cartilage, meniscus and inflammation.
Blood tests: to rule out other conditions (such as rheumatoid arthritis).
Osteoarthritis cannot be cured, but symptoms can be reduced:
Lifestyle: Weight loss, exercise (swimming, cycling).
Physical therapy: muscle strengthening and stability training.
Analgesics: Paracetamol, NSAIDs (e.g., ibuprofen) or topical gels.
Injections: Corticosteroids or hyaluronic acid.
Surgery: E.g., knee or hip replacement for severe wear and tear.
Osteoarthritis is not “old age wear and tear”: It can also develop at a younger age, especially after an injury.
Exercise remains crucial: It keeps muscles strong and joints flexible, even with osteoarthritis.
Pain from osteoarthritis in the knee occurs due to a combination of factors:
Wear and tear of cartilage:
The protective cartilage in the knee joint becomes thinner and more brittle. As a result, the bones (femur and tibia) rub against each other, causing pain. Although cartilage itself has no nerves, the pain is caused by irritation of surrounding structures.
Inflammatory reactions:
In osteoarthritis, mild inflammation often occurs due to the release of inflammatory substances (such as cytokines). These substances excite nerve endings in the joint, aggravating swelling and pain.
Bone changes (osteophytes):
The body tries to “repair” the joint by creating extra bone (osteophytes or “parrot jaws”). These nodules can press against surrounding tissues or nerves.
Irritation of the joint capsule and synovium:
The joint capsule (containing nerves) and the synovial fluid-producing layer can become inflamed (synovitis), causing immediate pain signals.
Muscle weakness and overexertion:
Muscles around the knee (such as the quadriceps) often weaken with less movement. This reduces stability, putting additional strain on the joint.
Damage to other structures:
Osteoarthritis often accompanies wear of the meniscus or ligaments (e.g., after an injury). This leads to additional mechanical pain with movement.
Mechanical stress:
Activities such as climbing stairs or standing for long periods of time increase the pressure on the affected joint. Being overweight significantly amplifies this effect.
Nerve irritation:
Swelling or osteophytes can pinch nerves (e.g., the saphenous nerve), causing radiating pain.
Psychological factors:
Chronic pain can lead to stress or gloom, making pain management worse (pain-brain connection).
Central sensitization:
Prolonged pain can make the nervous system hypersensitive, causing even small stimuli to be perceived as painful.
Risk factors that exacerbate pain:
Age, obesity, previous knee injuries, heavy loads (e.g., sports/work), and genetic predisposition.
In short, the pain in knee osteoarthritis is a complex interplay of mechanical wear and tear, inflammation, and changes in tissues and nerves. A combination of lifestyle modifications and medical treatments is often needed for relief.
Pain symptoms in knee osteoarthritis can be reduced through a combination of lifestyle modifications, non-drug treatments, medication and (in severe cases) surgery. Below is an overview of effective strategies:
Weight loss:
Every 5 kg of weight loss can reduce pressure on the knee by 15-30%. This slows wear and reduces pain.
Motion:
Muscle strengthening: Exercises for quadriceps, hamstrings and glutes (e.g. cycling, leg raises, walking) stabilize the knee.
Low-impact activities: swimming, aqua jogging or cycling put less strain on the joint.
Mobility exercises: Yoga or stretching improves flexibility and reduces stiffness.
Physical therapy:
A physical therapist can offer customized exercises and use techniques such as manual therapy or taping.
Heat/cold therapy:
Heat: Relaxes muscles and reduces stiffness (e.g., heat pad for activity).
Cold: Reduces swelling and acute pain (ice packs after exercise, maximum 15 minutes at a time).
Resources:
Knee brace or orthosis: Supports the joint and distributes pressure.
Orthotics or shoes with cushioning: Reduce shock when walking.
Adjustments in daily activities:
Avoid standing, squatting or climbing stairs for long periods of time. Use a cane if necessary.
Painkillers:
Paracetamol: First choice for mild pain (maximum 4x 500 mg/day).
NSAIDs (ibuprofen, naproxen): Reduce inflammation and pain, but have side effects (stomach, kidneys). Use short-term or in gel form (e.g., diclofenac gel).
Injections (possibly alternatives to Arthrosamid (with much shorter therapeutic effect):
Corticosteroids: Quick pain relief for inflammation (effect lasts for several weeks). NOT MORE OFTEN THAN ONCE!!! (due to adverse side effects on cartilage, bone and soft tissue and organs)
Hyaluronic acid: “Lubricates” the joint, effect can last for months (varying effect per person).
PRP (platelet-rich plasma) injections: Anti-inflammatory and growth factors important for many processes at the cellular level.
Dietary supplements:
Glucosamine and chondroitin may help some, but scientific evidence is limited.
Acupuncture:
May temporarily reduce pain via stimulation of pain-reducing nerve pathways.
TENS therapy:
Electrical stimulation of nerves reduces pain signals.
Cognitive behavioral therapy (CBT):
Helps manage chronic pain and reduce impact on daily life.
Mindfulness/relaxation techniques:
Reduce stress, which can lower pain perception.
Arthroscopy:
Useful only for mechanical problems (e.g., loose cartilage fragments).
Osteotomy:
Correction of leg position to redistribute pressure on the knee (e.g., in O-legs).
Knee replacement:
In cases of extensive damage, an artificial joint replaces the affected joint, often with good results.
If you suffer from osteoarthritis pain and the pain is not controlled with simple painkillers and lifestyle modifications, you might be suitable for treatment with Arthrosamid®. These symptoms are independent of the degree of osteoarthritis, grade 1-4. To find out if Arthrosamid® is right for you, consult your doctor.
Arthrosamid®, an intra-articular injection of polyacrylamide hydrogel (iPAAG), is a single-dose, non-biodegradable injection that provides long-acting symptomatic treatment to adult patients with knee osteoarthritis.
Arthrosamid® is absorbed into the synovial tissue of the inner joint capsule and reduces the inflammatory response by forming a natural barrier. In addition, it makes the joint capsule more elastic so that the nocisensor pain sensors will react less actively. Both result in less pain perception, less inflammation and improved mobility and functionality.
Arthrosamid® reduces pain and improves the function of the knee affected by osteoarthritis.
The non-absorbable, non-degradable and non-migratory properties of Arthrosamid® ensure long-lasting treatment of the knee, up to 5 years after a single treatment
Arthrosamid® is approved for the symptomatic treatment of knee osteoarthritis, so any patient with this condition may be eligible for it. However, treatment with Arthrosamid® is not suitable for everyone. Your doctor is the best person to advise you, but there are situations in which you should not use Arthrosamid® (contraindications)*:
*This is not a complete list of contraindications. Check with your doctor to see if Arthrosamid® can help you.
Arthrosamid is registered for the treatment of knee osteoarthritis.
When Arthrosamid is used for another synovial joint, the doctor will always ask for a so-called ” informed concent” statement. This statement indicates that you know that Arthrosamid is only registered for the treatment of knee osteoarthritis and that you know that research does not yet support treatment of another joint. In all likelihood, Arthrosamid works equally well in other synovial joints such as a hip or shoulder, but this has not yet been studied in humans. It has been studied in animals, however, and from this science we know that other joints also respond positively.
Arthrosamid® differs from the viscosupplementation injections such as hyaluronic acid (HA), platelet-rich plasma (PRP/ ACP), Kiomedin and regenerative stem cell therapy mainly due to its long-lasting effect. None of these products have research results where the therapeutic effect is 5 years except Arthrosamid.
Arthrosamid is the only product that actually permanently changes something physically, namely the structure of the joint capsule/ synovial tissue. Because of this permanent change, the body responds, allowing you to experience less pain, less inflammation and better function. Arthrosamid is not broken down or resorbed. All other products are broken down or resorbed, limiting the therapeutic effect time.
Research has shown that treatment with Arthrosamid can delay joint-replacement surgery for years. 56% of patients still did not have knee replacement surgery 10 years after a single treatment with Arthrosamid.
Treatment can be repeated as needed and on the advice of your doctor.
Keep in mind that Arthrosamid only starts to work really well after 3-4 months. 80% of patients who respond positively still have a positive treatment result even 5 years after a single treatment.
There have been cases where a patient has had repeat treatment and this has allowed them to function again for another 4 years without too many symptoms.
It is also possible to receive other treatment after Arthrosamid treatment, such as an artificial knee. Arthrosamid has no adverse effects on this treatment.
Research has shown that Arthrosamid® reduces pain for up to 5 years.
Aerthrosamid makes a permanent change to the capsule of the knee. As a result, the duration of action is up to 5 years after a single treatment. The joint capsule becomes thicker and more elastic and produces a more normal synovial fluid again which will permanently improve the knee’s function and you will have less inflammation, swelling, pain and the knee moves and functions better.
Arthrosamid fuses with the syniovial tissue of the joint capsule. Because of this fusion, the tissue becomes thicker and more elastic. As a result, it forms a natural barrier to the inflammatory cells, which are less able to function as a result. As a result, the inflammatory response decreases and swelling, as well as pain, decreases and functionality and mobility improve.
Arthrosamid provides long-term pain relief and improved functionality of the knee. About 80% of treated and studied patients respond positively to treatment. Younger patients respond better to treatment than older patients. Under the age of 60, 9 out of 10 patients respond positively. Between the ages of 60 and 70, 8 out of 10, and over 70, 6 to 7 out of 10 patients respond positively. Of the group who respond positively, the vast majority still have a positive effect after 5 years equal to the effect after year one.
Studies with Arthrosamid® have only been conducted for the treatment of knee osteoarthritis, so at this time it is only indicated for use in the knee. The knee is a so-called synovial joint just like the hip, shoulder ankle-foot fingers and toes. Given Arthrosamid’s mechanism of action, it is expected to work well in the other joints as well. Arthrosamid is also used in dogs and in horses (Arthramid Vet) and from veterinary science we know that this hydrogel also works equally well in the other joints.
Arthrosamid® is administered as a single injection into the joint gap of the knee by a qualified physician or ultrasound technician. The injection is performed simply in the doctor’s or ultrasound technician’s office, and you may return home immediately after treatment.
This website describes in detail how the treatment is performed on the page : Treatment.
Before you receive an injection of Arthrosamid®, you are also given a local anesthetic, usually Lidocaine, in and around the knee to be treated. This makes the injection less painful.
Some patients have a somewhat sensitive knee for a few days immediately after treatment. This goes away quickly.
If the knee becomes very painful and warm a few days after treatment and you develop a fever you should always contact the doctor. This could possibly indicate inflammation which almost never happens.
Arthrosamid® reduces your pain and stiffness and helps with movement. It has been shown to be safe and can provide long-term and persistent pain relief, improving your quality of life with one 6-mL injection.
As with any joint injection treatment, it is wise to take it easy for the first few days after the injection and to move the knee sufficiently without putting too much strain on it. After a week you can resume your normal activities.
During the first week after injection, some transient reactions related to the injection may occur, such as mild to moderate pain at the injection site or swelling around the knee.
The response to treatment varies greatly between patients.
Some experience no improvement for the first few weeks after injection and only experience positive results after a longer period of time. Arthrosamid® really has to “grow into” the capsule before it starts to work. Most patients experience an onset of action between 6 weeks and 4 months.
Others, on the contrary, experience a marked improvement immediately after treatment. Often after about a week the old symptoms return. These then disappear very slowly and after only 3-4 months you notice that you have almost no more trouble with the knee.
The differences in how patients respond is enormous. Studies have shown that 80% of patients respond positively to treatment. The treatment effect is greatest in patients under the age of 70.
Arthrosamid® intra-articular polyacrylamide gel is safe for its intended use in the treatment of pain symptoms in knee osteoarthritis. The most common adverse events (side effects) in clinical trials were injection-related mild to moderate pain and or mild swelling during the first weeks after injection. No long-term adverse events were known.
More than 1,800,000 treatments have now been performed with this hydrogel over the past 25 years with no known negative side effects that can be related to the hydrogel.
Should it be necessary in the future to place a knee replacement, this is simply possible after treatment with Arthrosamid.
Treatment with Arthrosamid is not reimbursed.
Arthrosamid is a relatively new treatment for osteoarthritis, with studies showing that it provides effective relief for up to five years.
In Belgium and the Netherlands, treatment guidelines for hip and knee osteoarthritis are revised approximately every 5 to 10 years. These guidelines determine which treatments are recommended by orthopedic surgeons and other medical professionals, such as general practitioners and physical therapists. Although Arthrosamid may be considered in the next revision, it is unlikely to be included immediately as the first treatment option. The scientists developing these guidelines require extensive evidence before new therapies are included, given their conservative approach that carefully weighs all options and interests. This raises the question of whether corticosteroid injections should be subject to the same rigorous assessment, given current knowledge.
Health insurers strictly enforce these guidelines and reimburse treatments only if they are included in them. However, a recent study shows that this policy is not always cost-effective. An analysis of patient data over a 10-year period shows that 56% of patients who received a single Arthrosamid injection at the time have not had joint replacement surgery to date (April 2025). This suggests that targeted use of Arthrosamid in patients younger than 70 years of age could result in significant savings for insurers.
We are committed to raising awareness of the possibilities of Arthrosamid and hope that health insurance companies will fully or partially reimburse for the treatment in the future. In some European countries we are currently investigating whether reimbursement is a possibility. Together we can contribute to wider acceptance of this innovative treatment.
