Thumb Arthritis Injections: Corticosteroids, Hyaluronic Acid, PRP, and Emerging Treatments

What injections are given for thumb arthritis?

For individuals experiencing the pain and functional limitations of thumb arthritis, particularly at the carpometacarpal (CMC) joint, several injectable treatments are available, primarily aimed at reducing inflammation, improving lubrication, or stimulating tissue repair. The most common injections include corticosteroids, hyaluronic acid (viscosupplementation), and platelet-rich plasma (PRP).

Understanding Thumb Arthritis

Thumb arthritis, medically known as carpometacarpal (CMC) joint osteoarthritis, affects the joint at the base of the thumb, where the thumb metacarpal bone meets one of the wrist bones (the trapezium). This condition involves the progressive degeneration of the articular cartilage that cushions the ends of these bones, leading to bone-on-bone friction, inflammation, pain, stiffness, and a significant reduction in grip strength and dexterity. It is a common condition, especially among women and older adults, severely impacting daily activities like pinching, gripping, and twisting.

The Role of Injections in Management

When conservative treatments such as rest, splinting, anti-inflammatory medications, and physical therapy no longer provide adequate relief, injections become a valuable next step in the management of thumb arthritis. The primary goals of injection therapy are to:

• Reduce Pain: Alleviate the discomfort associated with joint inflammation and degeneration.
• Decrease Inflammation: Target the inflammatory processes that contribute to pain and tissue damage.
• Improve Function: Enhance the joint's mobility and strength, thereby improving the ability to perform daily tasks.
• Delay Surgical Intervention: Provide symptomatic relief that may postpone or even avoid the need for surgery.

It's crucial to understand that injections for arthritis are typically palliative, meaning they address symptoms rather than curing the underlying condition.

Corticosteroid Injections

Corticosteroid injections are one of the most common and longest-standing treatments for various forms of osteoarthritis, including thumb arthritis.

• Mechanism of Action: Corticosteroids are powerful anti-inflammatory agents. When injected directly into the joint space, they work by suppressing the immune response and reducing the production of inflammatory chemicals, thereby decreasing pain and swelling.
• Procedure: The injection is typically performed in a clinical setting by a physician. The thumb is often stabilized, and the injection site may be numbed with a local anesthetic. Imaging guidance (such as fluoroscopy or ultrasound) may be used to ensure accurate placement of the medication into the small CMC joint.
• Efficacy: Many patients experience significant pain relief and improved function following a corticosteroid injection, often lasting for several weeks to months. However, the effects are temporary, and the pain typically returns.
• Potential Side Effects: While generally safe, potential side effects include temporary increase in pain (flare-up), infection, skin discoloration or atrophy at the injection site, and, rarely, tendon weakening or rupture. Repeated injections into the same joint are generally limited due to concerns about potential cartilage damage and other systemic side effects.

Viscosupplementation (Hyaluronic Acid) Injections

Viscosupplementation involves injecting hyaluronic acid (HA) into the joint. HA is a natural component of synovial fluid, which lubricates and acts as a shock absorber in healthy joints.

• Mechanism of Action: In arthritic joints, the natural HA in synovial fluid becomes thinner and less effective. Injecting exogenous HA aims to restore the lubricating and shock-absorbing properties of the joint fluid, potentially reducing pain and improving mobility. Some research also suggests HA may have anti-inflammatory effects and could potentially stimulate the body's own HA production.
• Procedure: Similar to corticosteroid injections, HA is injected directly into the joint space, sometimes under imaging guidance. Unlike corticosteroids, HA injections are often administered as a series of 1-3 injections over several weeks, depending on the specific product used.
• Efficacy: The evidence for the efficacy of HA injections in thumb CMC arthritis is mixed. Some studies show modest benefits in pain relief and function, particularly in earlier stages of arthritis, while others show no significant advantage over placebo or corticosteroids. Benefits, when present, can last for several months.
• Potential Side Effects: Side effects are usually mild and localized, including temporary pain, swelling, or stiffness at the injection site. Allergic reactions are rare.

Platelet-Rich Plasma (PRP) Injections

PRP therapy involves using a patient's own blood components to stimulate healing and reduce inflammation.

• Mechanism of Action: A small sample of the patient's blood is drawn and then spun in a centrifuge to separate the platelets, plasma, and red blood cells. The concentrated platelet-rich plasma, containing a high concentration of growth factors and other bioactive proteins, is then injected into the affected joint. These growth factors are believed to promote tissue repair, modulate inflammation, and potentially stimulate cartilage health.
• Procedure: The entire process, from blood draw to injection, is typically completed within an hour in an outpatient setting. Ultrasound guidance is often used for precise placement into the small CMC joint.
• Efficacy: PRP for thumb arthritis is considered an emerging treatment. While anecdotal evidence and early research suggest promising results in terms of pain reduction and improved function, larger, high-quality randomized controlled trials are still needed to definitively establish its long-term efficacy and optimal protocols.
• Potential Side Effects: Because PRP uses the patient's own blood, the risk of allergic reaction or disease transmission is minimal. The most common side effects are temporary pain, swelling, or bruising at the injection site.

Other Emerging & Less Common Injections

While corticosteroids, HA, and PRP are the most commonly discussed injections, other options are under investigation or used in specific contexts:

• Stem Cell Injections: These involve injecting mesenchymal stem cells (MSCs), often derived from the patient's bone marrow or adipose tissue, into the joint. MSCs have potent anti-inflammatory and regenerative properties. This is a highly experimental and costly treatment, with limited robust evidence for routine use in thumb arthritis.
• Prolotherapy: This involves injecting an irritant solution (often dextrose) into the ligaments and tendons around a joint, with the aim of stimulating a localized inflammatory response that promotes tissue healing and strengthening. Evidence for its effectiveness in arthritis is less robust compared to other injection types.

Considerations Before Receiving an Injection

Before opting for any injection, a thorough discussion with a hand specialist, rheumatologist, or orthopedic surgeon is essential. Key considerations include:

• Accurate Diagnosis: Confirming that the pain is indeed due to CMC arthritis and not another condition.
• Stage of Arthritis: The effectiveness of some injections may vary depending on the severity of cartilage damage.
• Risks vs. Benefits: Understanding the potential side effects and the expected duration of relief.
• Not a Cure: Injections are typically part of a comprehensive management plan and do not reverse the underlying degenerative process.
• Complementary Therapies: Injections are often most effective when combined with physical therapy, activity modification, splinting, and oral pain management strategies.

The Future of Injection Therapy for Thumb Arthritis

Research continues to explore new injectable agents and refine existing techniques to offer more durable and potentially regenerative solutions for thumb arthritis. Advances in biological therapies, including more targeted growth factors, advanced stem cell techniques, and personalized medicine approaches, hold promise for future treatments that may not only alleviate symptoms but also slow or even reverse the progression of joint degeneration.