Knee Gel Injections: Understanding Viscosupplementation for Osteoarthritis

How is gel injected into the knee?

Gel is injected into the knee through a precise medical procedure known as viscosupplementation, typically performed by a healthcare professional to introduce hyaluronic acid directly into the joint space, aiming to restore lubrication and reduce pain in individuals with osteoarthritis.

Understanding Knee Osteoarthritis and Viscosupplementation

Knee osteoarthritis (OA) is a degenerative joint disease characterized by the breakdown of cartilage, leading to pain, stiffness, and reduced mobility. The natural synovial fluid within the knee, which lubricates the joint and absorbs shock, contains hyaluronic acid (HA). In OA, the quality and quantity of this HA diminish.

Viscosupplementation is a medical procedure that involves injecting a gel-like substance, primarily hyaluronic acid, directly into the knee joint. The goal is to supplement the knee's natural synovial fluid, improving its viscoelastic properties. This aims to:

• Enhance lubrication: Reducing friction between the articulating bones.
• Improve shock absorption: Protecting the joint from impact forces.
• Reduce pain: Alleviating discomfort caused by bone-on-bone rubbing.
• Potentially decrease inflammation: Through the biological effects of HA on joint tissues.

Who Administers the Injection?

Viscosupplementation injections are medical procedures that must be performed by a qualified healthcare professional. This typically includes:

• Orthopedic surgeons
• Sports medicine physicians
• Rheumatologists
• Pain management specialists
• Physiatrists (physical medicine and rehabilitation physicians)

These professionals possess the anatomical knowledge and procedural skills necessary to ensure safe and effective injection.

The Pre-Injection Process

Before the injection, several steps are taken to prepare the patient and the injection site:

• Patient Consultation and Assessment: The healthcare provider will thoroughly review the patient's medical history, current medications, allergies, and previous treatments. A physical examination of the knee will be conducted to confirm the diagnosis of osteoarthritis and assess the suitability for viscosupplementation. X-rays or other imaging may be reviewed.
• Informed Consent: The procedure, its benefits, risks (e.g., pain, swelling, infection, allergic reaction), and alternatives will be explained to the patient, who must provide informed consent.
• Preparation of the Injection Site:
  • The skin around the knee will be thoroughly cleaned with an antiseptic solution (e.g., chlorhexidine or iodine) to minimize the risk of infection.
  • A local anesthetic (e.g., lidocaine spray or injection) may be applied to numb the skin and superficial tissues, reducing discomfort during the needle insertion.

The Injection Procedure: A Step-by-Step Guide

The actual injection process is precise and typically takes only a few minutes:

1. Patient Positioning: The patient is usually positioned lying on their back with the knee slightly bent or straight, depending on the preferred approach for optimal joint access.
2. Locating the Injection Site: The healthcare provider will carefully palpate the knee to identify the specific landmarks for joint entry. To ensure accuracy and safety, especially in cases of severe OA or complex anatomy, imaging guidance is frequently used:
   • Ultrasound Guidance: A handheld ultrasound probe is used to visualize the joint space, surrounding tissues, and the needle in real-time. This allows the provider to precisely guide the needle to the correct location and avoid vital structures.
   • Fluoroscopy Guidance: This involves using continuous X-ray imaging to visualize the knee joint. A small amount of contrast dye may be injected first to confirm needle placement within the joint space before the HA gel is administered.
3. Aspiration (If Needed): If there is excess fluid (effusion) in the knee joint, the provider may first aspirate (draw out) this fluid using the same needle before injecting the hyaluronic acid. This can help reduce pressure and improve the effectiveness of the HA.
4. Injection of the Viscosupplement: Once the needle is confirmed to be in the correct intra-articular space, the pre-filled syringe containing the hyaluronic acid gel is attached, and the gel is slowly and steadily injected into the joint. The gel's viscous nature requires a controlled, deliberate injection.
5. Post-Injection Immediate Care: After the injection, the needle is withdrawn, and a sterile bandage or dressing is applied to the injection site. Pressure may be applied briefly to prevent bruising.

Post-Injection Care and Recovery

Following the injection, specific care instructions are provided to optimize outcomes and minimize complications:

• Activity Restrictions: Patients are typically advised to avoid strenuous activities, heavy lifting, and prolonged standing for 24-48 hours. Light activities like walking are generally permissible.
• Common Side Effects:
  • Mild pain, swelling, warmth, or tenderness at the injection site. These are usually temporary and can be managed with ice packs and over-the-counter pain relievers (e.g., acetaminophen).
  • A temporary increase in knee pain or stiffness, sometimes referred to as a "flare-up," can occur in the first few days.
• Expected Outcomes and Timeline: The full benefits of viscosupplementation are not immediate and may take several weeks to become noticeable as the HA integrates with the synovial fluid. The duration of pain relief varies among individuals, typically lasting from a few months up to a year. A series of injections (e.g., 1 to 5, depending on the specific product) may be required.
• When to Seek Medical Attention: Patients should contact their healthcare provider if they experience:
  • Severe or worsening pain.
  • Significant swelling or redness.
  • Signs of infection (fever, chills, warmth spreading from the site).
  • Numbness or weakness in the leg.

Efficacy and Considerations

Viscosupplementation is not a cure for osteoarthritis but rather a symptomatic treatment.

• Who is a Candidate? It is typically considered for individuals with mild to moderate knee OA who have not found sufficient relief from conservative treatments like oral pain medications, physical therapy, or corticosteroid injections.
• Limitations and Alternatives: The effectiveness of viscosupplementation can vary. It may not be suitable for severe OA where there is significant cartilage loss and bone-on-bone contact. Alternatives include physical therapy, weight management, oral medications, corticosteroid injections, and, ultimately, surgical options like knee replacement.
• Evidence-Based Perspective: While some studies show modest benefits, particularly in the short-to-medium term, the overall evidence for viscosupplementation's long-term efficacy and disease-modifying effects is mixed. Its use is often part of a comprehensive treatment plan tailored to the individual patient.

Conclusion

The injection of gel (hyaluronic acid) into the knee is a precise medical procedure aimed at alleviating symptoms of knee osteoarthritis by supplementing the joint's natural lubrication. Performed by skilled medical professionals, often with imaging guidance, it involves careful preparation, accurate needle placement, and specific post-procedure care. While not a definitive cure, viscosupplementation offers a valuable option for managing pain and improving function for suitable candidates as part of a holistic approach to knee health.