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What are Hydrogel Injections?

Hydrogel injections are a novel, non-surgical approach for the treatment of pain, stiffness, and disability of joint osteoarthritis. It is a non-biodegradable and biocompatible injection that consists of 97.5% non-pyrogenic water and 2.5% cross-linked polyacrylamide. Your physician administers the hydrogel injection into the joint, where it works to lubricate and cushion the joint. One hydrogel injection can improve the pain and stiffness of joint osteoarthritis for up to 2 years. The result is improved joint function, providing patients with sustained relief by reducing stiffness and pain and improving the overall quality of life.

Indications for Hydrogel Injections

Your physician may recommend hydrogel injections for osteoarthritis of the joints, such as the knee, hips, and shoulder joints when conservative treatment measures such as exercise, medications, and viscosupplement injections have failed to relieve pain associated with joint osteoarthritis. Osteoarthritis is a degenerative joint disease that causes breakdown and eventual loss of cartilage in the joint, causing a painful rubbing of bone surfaces with movement. Hydrogel is administered into the joint to cushion and lubricate the joint and relieve pain.

How Do Hydrogel Injections Work?

A joint is an articulation (junction) between 2 or more bones in the body. Muscles, tendons, ligaments, and other soft tissue structures hold the joint in position. The joint surface is covered by smooth articular cartilage that cushions and enables smooth movement of the joint. To further reduce friction between the articulating surfaces of the bones, the joint is lined by a synovial membrane that produces a thick clear fluid called synovial fluid. This fluid lubricates and nourishes the cartilage and bones inside the joint capsule. Hydrogel injections when injected into the joint cavity, integrate with the synovial membrane and thickens the synovial fluid surrounding the joint. It works to restore viscosity within the synovial fluid and improve lubrication and cushioning of the joint to relieve pain and inflammation connected with osteoarthritis of the joint.

Procedure for Hydrogel Injections

Hydrogel injection is a minimally invasive procedure that is most commonly carried out in an outpatient setting under fluoroscopy (live X-ray) or ultrasound guidance - this is because the hydrogel should be injected precisely into the intra-articular cavity rather than the soft tissue outside the joint. If you administer a drug into the joint without guidance, the accuracy is only 80 percent. Hence, 1 in 5 injections done without guidance does not get in the joint resulting in reduced efficiency. In general, the procedure involves the following steps:

  • The affected joint surface is thoroughly cleaned and sterilized with an antiseptic solution.
  • A local anesthetic is administered at the joint area to numb the area to be injected.
  • Under ultrasound or fluoroscopy guidance, your doctor will then insert a needle into the knee joint cavity and the hydrogel is delivered through the needle directly into the joint.
  • The hydrogel works by integrating into the synovial tissue of the inner joint capsule and thickens the synovial membrane.
  • As the hydrogel is non-migratory, non-biodegradable, and non-absorbable, it provides durable cushioning of the inner capsular tissue, helps decrease joint pain and stiffness, and improves the overall function of the joint within days.
  • The needle is removed, and a plaster is placed over the injection site.

Post-Procedure Care and Recovery

Following the hydrogel injection, you may feel slight discomfort when the effect of the local anesthetic wears off, but otherwise, the injection should be well tolerated. You may notice mild to moderate pain and/or swelling at the injection site. You are advised to look out for any signs of infection, particularly swelling, tenderness, oozing, or warmth at the injection site or systemic symptoms such as a fever. Medications are provided as needed to address pain, infection, and other symptoms. You should refrain from strenuous activities such as running or lifting weights for the first few days after your injection. You should be able to feel pain relief within weeks of the hydrogel injection.

Risks and Complications

Hydrogel injection is a well-tolerated procedure with minimal side effects. The most common side effect is temporary pain and discomfort at the injection site. The joint may also feel distended or full. In addition, Baker’s cyst (a fluid-filled growth behind the knee) may occur. Rare side effects include infection and allergic reactions.

  • AO North America
  • American Shoulder And Elbow Surgeons
  • American Orthopaedic Society for Sports Medicine
  • American Academy of Orthopaedic Surgeons
  • American Medical Association