What is Hydrogel (Liquid Knee Replacement)?

Osteoarthritis is a disease of the joints and occurs as a result of wear and tear of the cartilage tissue over time. Cartilage is a smooth and elastic tissue that connects joints and covers the ends of bones. This tissue prevents the bones from rubbing against each other and allows the joints to move freely. Osteoarthritis is the thinning and wear and tear of this cartilaginous tissue, causing the bones to rub against each other and causing pain.

Knee arthritis is a type of this condition that occurs in the knee joint. It is common in older people but can also occur in young people. Factors that cause knee arthritis include genetic predisposition, overweight, previous trauma to the knee and overuse.

Osteoarthritis of the knee develops over a long period of time and can severely limit life as it progresses. Patients usually experience symptoms such as pain, swelling, limitation of movement and joint deformities. This can have a negative impact on a person’s daily life. For example, even simple movements such as climbing stairs, taking long walks or squatting can become challenging and painful.

Although there is no definitive cure for knee arthritis, various treatment methods can be applied to relieve pain, reduce movement limitations and improve quality of life. These include medication, physical therapy, knee braces, intra-articular injections and surgical interventions (when necessary).

In the treatment of knee arthritis, injections into the knee are among the frequently preferred methods. In this article, we will give information about “intra-articular hydrogel injection”, which has been used in the treatment of knee arthritis in the last few years. This method is scientifically known as “polyacrylamide hydrogel” (PAAG). It is popularly known as “liquid knee replacement”.

Read the rest of our article to find out how the hydrogel injection is applied and whether it really has an effect.

Contents:

• Factors Affecting Method Selection in Knee Osteoarthritis Treatment
• What is Hydrogel and What are its Uses?
• Hydrogel Treatment for Knee Osteoarthritis
• How is Hydrogel Injection Applied?
• After Hydrogel Injection
• What are the Side Effects of Hydrogel Injection?
• Who is not suitable for hydrogel injection?

Factors Affecting Method Selection in Knee Osteoarthritis Treatment

Which method to choose for the treatment of knee arthritis depends on several different factors. These include the stage of the disease, the patient’s age, general health, pain level and lifestyle.

• Stage of the disease: Knee arthritis is usually classified into four stages. In the early stages, there is mild pain and limitation of movement, while in advanced stages the cartilage loss can be more serious. In the early stages, medication and physical therapy are usually recommended, while surgical intervention may be required in advanced stages.
• Patient Age and General Health Status: The patient’s age and general health status also affect treatment options. For example, some older patients may not be suitable for surgical intervention and conservative treatment methods may be preferred.
• Pain Level: The severity of the pain experienced by the patient can also influence the choice of treatment method. For mild pain, painkillers and anti-inflammatory drugs may be sufficient, while for severe pain, stronger treatment methods may be used.
• Lifestyle: The patient’s daily activities, work and hobbies can influence the choice of treatment. For patients with an active lifestyle, the goal of treatment will be to restore mobility as much as possible.
• Patient’s Preferences and Expectations: Finally, the patient’s own preferences and expectations also play an important role in the choice of treatment modality. Some patients may prefer to avoid surgery, while others may be open to surgical options for faster recovery.

All these factors are evaluated through discussions between the doctor and the patient and the most appropriate treatment method is determined.

Knee Pain Assessment Test

What is Hydrogel and What are its Uses?

Hydrogels, which are used as a new method in the treatment of knee joint arthritis, were first introduced in 1960. Their first use was in the production of contact lenses. Hydrogels are smart biomaterials that can absorb large amounts of water and thus exhibit swelling properties.

Hydrogels generally have a jelly-like, elastic and flexible consistency. Since they have a high water content, they have a very similar structure to living tissue. Therefore, it is not perceived as a foreign body when injected into the body. Its structure, which is compatible with the body, has been a major factor in its use in the field of medicine. But hydrogels are used in many different fields, not only in medicine. Pharmacy, cosmetics, chemistry, agriculture and food are other areas where hydrogels are used.

Although it does not include all uses of hydrogels, the most important applications in medicine are listed below:

• Orthopedic applications
• In cases of urinary incontinence such as stress incontinence
• Contact lenslerde
• In drug delivery systems
• In cancer treatment
• In cases of spinal cord regeneration
• Wound care and healing
• As filling in facial aesthetics

In addition to these uses, hydrogels have recently come to the agenda in the treatment of knee arthritis and their applications have started in our country. But are hydrogel injections really effective in the treatment of knee arthritis? How long does this effect last? These issues will be addressed in the following chapters.

Hydrogel Treatment for Knee Osteoarthritis

The use of polyacrylamide (PAAG) hydrogel injected intra-articularly is quite new in the treatment of knee osteoarthritis.

Since the hydrogel is compatible with body biology, it can be injected into the knee joint as a sterile gel. This gel consists of 97.5% sterile water and 2.5% polyacrylamide. Polyacrylamide prevents the hydrogel from biodegrading. Therefore it cannot be absorbed and broken down by the human body.

The hydrogel injection is administered into the knee joint cavity and integrates with the synovial tissue. Thus, the synovial membrane thickens. And what does that mean? The knee joint is lined with a special thin membrane (synovium) made of small synovial cells. The synovial membrane is responsible for the production of the natural lubricating fluid in the joint. This synovial fluid, also known as joint fluid, is effective in performing knee movements comfortably. When there is a problem in the joint, inflammation of the synovial membrane, synovitis, develops.

Hydrogel injection can help reduce synovial inflammation by creating a stable and long-lasting layer covering the surface of the synovial membrane.

Within a few weeks of adhering to the synovial membrane, the hydrogel starts to integrate into the adjacent joint capsule and acts as a scaffold. In other words, it creates a kind of cushion inside the joint, helping the joint to bear the load. The hydrogel also strengthens the joint capsule and makes it more elastic.

How is Hydrogel Injection Applied?

Hydrogel injection is a procedure performed in a clinical setting and under sterile conditions. The hydrogel is injected into the knee joint with a needle. At the beginning of the procedure, the patient is given a single dose of antibiotics to reduce the risk of infection. In addition, a small amount of local anesthetic (a drug that numbs a specific area) can be used to relieve pain that may occur during the procedure.

Prior to the hydrogel injection, an ultrasound scan may be performed to determine the most appropriate site for the injection and the level of fluid present in the knee joint. If there is excess fluid in the knee joint, it must be drained before the hydrogel injection.

After Hydrogel Injection

After the hydrogel injection, the patient should be monitored for 10-15 minutes to make sure there are no side effects. After the local anesthetic wears off, mild joint pain and swelling may occur. In this case, some painkillers may need to be continued.

After the injection, the knee should be rested for at least 2-3 days. Strenuous activities should be avoided to minimize the risk of inflammation and flare-ups. For example, activities that actively use the knee, such as running and long walking, should be avoided.

The benefit of the injection usually starts to be noticeable 4 weeks after administration. It can take up to 12 weeks for the hydrogel needle to take full effect. Since the hydrogel is not broken down by the body, it is claimed to relieve pain for longer.

The orthopaedic doctor and physiotherapist will recommend a tailored exercise program for each patient and provide guidance on additional treatments. Because a holistic approach is adopted in the treatment of knee arthritis and some treatment methods are used together.

What are the Side Effects of Hydrogel Injection?

Previous studies have shown that intra-knee injections using polyacrylamide (PAAG) hydrogel are generally well received by patients. However, as with any medical procedure, this method may have some side effects. Possible side effects of the hydrogel are as follows:

• Knee Pain and Swelling: After a hydrogel injection, pain and swelling in the knee may occur for a few days or a few weeks.
• Limitation of Movement: Some patients may experience decreased knee range of motion or stiffness in the knee after injection.
• Sensory Changes: Sensory changes such as tingling, numbness, coldness or warmth in the leg may occur.
• Risk of Infection: Although rare, there is a risk of infection after hydrogel injection.
• Allergic Reactions: Also in rare cases, some patients may have allergic reactions to the injected substance.

It is important to contact a healthcare professional immediately if you experience any of the above side effects or if anything unexpected occurs.

Who is not suitable for hydrogel injection?

Although hydrogel injection is a treatment that can benefit many patients, it may not be suitable for everyone. People with the following conditions are advised not to undergo hydrogel injection treatment:

• Infection Status: People with an existing infection inside the knee or on the skin.
• Recent Surgeries: Knee arthroscopy within the last 6 months.
• People with Knee Replacement: People who have undergone knee replacement surgery and received an artificial knee joint.
• People with Knee Implants: Those with any implant in the knee joint.
• Recent Injections: Those who have recently had hyaluronic acid injections.
• Certain Health Conditions: People with conditions that can affect joints, such as hemophilia, autoimmune diseases, lupus, rheumatoid arthritis.

People experiencing these and similar conditions should consult their doctor for appropriate treatment options and alternative therapies.

Conclusion: Is Hydrogel Therapy for Knee Osteoarthritis Really Effective?

Ongoing research for the treatment of knee arthritis is also increasing interest in non-surgical treatment methods. Patients and physicians have high hopes for non-surgical methods, but surgical intervention may become inevitable if arthritis progresses. Among these methods, hydrogel intra-knee injection has become popular in recent years and has been claimed to cure knee arthritis without surgery.

Studies and clinical experience on the efficacy of hydrogel therapy for knee osteoarthritis suggest that this method has the potential to reduce pain and improve joint function in some patients. According to the data, these positive effects can last up to three years. However, five- and ten-year follow-up studies are still ongoing.

While the potential benefits of hydrogel therapy are promising, more data and extensive research is needed on its long-term effects, side effects and overall effectiveness. In addition, hydrogel treatment may not be as effective in all patients. In some cases, it may postpone the need for surgical intervention, but not completely eliminate it.

There are also some limitations and disadvantages of hydrogel treatment. The high cost of hydrogel therapy and the risk of side effects in certain patients are among the factors limiting access to treatment and creating an economic burden for some patients.

As a result, there is no “one-size-fits-all” solution for treating osteoarthritis of the knee. Hydrogel treatment can be an effective option for certain conditions. However, the most appropriate treatment method should be determined in line with the patient’s specific condition, the symptoms they are experiencing and the recommendations of their doctor. It is important to contact your healthcare professional for more detailed information about the most effective and appropriate treatment for you.

You can use the knee pain assessment test to find out the extent of your knee arthritis. You can contact us for information about the most appropriate and effective treatment for you.

Frequently Asked Questions

Has hydrogel therapy been approved for use?

Yes, PAAG (Polyacrylamide Hydrogel) Hydrogel is approved in some regions for the treatment of osteoarthritis of the knee. Hydrogel therapy, for example, qualified for CE certification from Europe in 2021 and has been accepted for use in the treatment of knee arthritis. However, in the United States, the treatment is still under evaluation by the Food and Drug Administration (FDA) and is being scrutinized for efficacy and safety.

We recommend that you consult an orthopedic specialist to decide whether hydrogel treatment is right for you. Your orthopedic doctor will advise and guide you on the most appropriate treatment options, taking into account the current condition of your knee, your general health and other factors.

What is the difference between hyaluronic acid and hydrogel applied intra-articularly in arthritis?

PAAG Hydrogel and hyaluronic acid are two different substances used in the treatment of knee arthritis. Each has different characteristics and ways of implementation.

• PAAG Hydrogel: Hydrogel is a polyacrylamide gel-based material with a high capacity to hold water molecules. When injected into the joint, the hydrogel creates a cushion effect inside the joint, relieving pain and facilitating movement.

It integrates with the synovial (intra-articular membrane) lining of the joint and is indestructible. It usually provides a long-lasting effect with a single injection.

• Hyaluronic Acid: Hyaluronic acid is a naturally occurring substance in the body that increases the fluidity and elasticity of the fluid in the joints. Hyaluronic acid injected into the joint in the treatment of knee arthritis mimics the joint fluid and provides lubrication. However, hyaluronic acid may often require repeated injections. Because it is absorbed by the body over time.

Although both treatment modalities are used in the treatment of osteoarthritis of the knee, they differ in their effects, frequency of application and cost. Based on the patient’s condition and needs, the doctor will determine the most appropriate course of treatment.

Can the hydrogel be used for arthritis of other joints such as the hip joint?

Although some doctors have applied PAAG hydrogel to other joints, such as the hip and shoulder, it is currently only approved for use in the knee joint. Therefore, there is still insufficient information on the efficacy, safety and potential risks of hydrogel therapy for other joints.

Should I inform my doctor/dentist about my hydrogel treatment?

Yes, you must inform your doctor or dentist if you have had hydrogel treatment. During surgical or dental procedures, any infection in the body can reach and lodge in your knee joint. The infection that settles in the hydrogel may be resistant to antibiotics. This can lead to joint infection, which may require surgical intervention on the knee joint. It is therefore important that your doctor and dentist are fully informed about your current state of health and the treatments you are undergoing.

Can the hydrogel be used in the treatment of inflammatory rheumatic joints?

The hydrogel was developed specifically for the treatment of degenerative joint diseases such as arthritis. Inflammatory rheumatic diseases, such as rheumatoid arthritis, often develop due to systemic inflammation and abnormal activity of the immune system. Anti-inflammatory drugs and other specialized treatments are often used for such conditions.

Hydrogel therapy is not specifically designed for the treatment of inflammatory rheumatic joint diseases and there is insufficient clinical data on this. It is therefore important to follow your doctor’s recommendations to determine the most appropriate treatment for rheumatic joint diseases.