Subtalar Joint Injections: Common Side Effects, Serious Risks, and When to Seek Help

What are the side effects of subtalar joint injections?

Subtalar joint injections, while generally safe and effective for pain management and diagnosis, can be associated with a range of side effects, from common, mild, and temporary discomforts to less frequent but potentially more serious complications.

Understanding Subtalar Joint Injections

The subtalar joint, located just below the ankle joint, plays a crucial role in foot mechanics, enabling inversion and eversion. When this joint experiences inflammation, arthritis, or injury, it can lead to significant pain and functional limitation. Subtalar joint injections are a common medical procedure, typically involving corticosteroids (to reduce inflammation and pain) or hyaluronic acid (for lubrication) and sometimes local anesthetics. They serve both diagnostic purposes (confirming the joint as the source of pain) and therapeutic ones (providing symptomatic relief). While often beneficial, understanding the potential side effects is crucial for informed patient care and management.

Common and Expected Side Effects

The most frequently encountered side effects are usually mild, localized, and transient, resolving within a few days of the injection. These include:

• Injection Site Pain or Soreness: It is common to experience some localized pain, tenderness, or aching at the site where the needle was inserted. This typically subsides within 24-48 hours.
• Bruising: Minor bruising around the injection site is possible due to the needle puncturing small blood vessels. This usually resolves within a week.
• Swelling: Slight swelling in the immediate area can occur, often accompanied by the localized pain.
• Temporary Increase in Pain (Steroid Flare): For corticosteroid injections, some individuals may experience a temporary worsening of pain, often described as a "flare," within the first 24-48 hours post-injection. This is thought to be an inflammatory reaction to the corticosteroid crystals and usually resolves on its own or with ice and over-the-counter pain relievers.
• Skin Discoloration: Rarely, temporary lightening or darkening of the skin at the injection site can occur, particularly in individuals with darker skin tones.
• Nerve Irritation: Transient numbness or tingling in the foot or ankle may occur if the needle temporarily irritates a superficial nerve. This is usually short-lived.

Less Common but More Serious Side Effects

While rare, more significant complications can arise, necessitating immediate medical attention. Awareness of these potential issues is vital for both patients and healthcare providers.

• Infection: This is a serious but rare complication (septic arthritis), where bacteria are introduced into the joint space. Symptoms include:
  • Severe, rapidly worsening pain
  • Significant warmth, redness, and swelling around the joint
  • Fever and chills
  • General feeling of malaise
• Allergic Reaction: Though uncommon, an individual may have an allergic reaction to the medications injected (e.g., local anesthetic, corticosteroid, preservative). Symptoms can range from mild skin rash (hives) to severe anaphylaxis, which is a medical emergency characterized by:
  • Difficulty breathing
  • Widespread rash and itching
  • Swelling of the face, lips, or throat
  • Dizziness or lightheadedness
• Nerve Damage: While rare, direct trauma to a nerve by the needle or prolonged compression from swelling can lead to more persistent numbness, weakness, or altered sensation (paresthesia) in the distribution of the affected nerve.
• Tendon or Ligament Damage: Repeated corticosteroid injections into or near tendons can weaken collagen fibers, increasing the risk of tendon rupture. While less common around the subtalar joint compared to other areas, it remains a consideration.
• Skin and Fat Atrophy: Corticosteroid injections can, over time, lead to localized thinning of the skin (atrophy) or loss of subcutaneous fat, resulting in a dimple or depression at the injection site. This is more common with superficial injections.
• Bleeding: While minor bruising is common, significant bleeding or hematoma formation can occur, especially in individuals on anticoagulant medications.
• Systemic Effects of Corticosteroids: Although the dose is localized, a small amount of corticosteroid can be absorbed into the bloodstream, potentially causing temporary systemic effects. These are more likely with higher doses or frequent injections and may include:
  • Temporary elevation of blood sugar levels (important for diabetics to monitor)
  • Facial flushing
  • Temporary mood changes or insomnia
  • Fluid retention
• Cartilage Damage/Osteonecrosis: While controversial, some studies suggest that repeated high-dose corticosteroid injections into weight-bearing joints could theoretically contribute to cartilage degradation or osteonecrosis (bone death) over the long term, though this is not a universally accepted finding for the subtalar joint in routine clinical practice.

Long-Term Considerations

While a single or infrequent subtalar joint injection is generally considered safe, repeated or frequent injections, particularly of corticosteroids, warrant careful consideration due to potential long-term effects. These include the cumulative risk of tendon weakening, skin/fat atrophy, and theoretical concerns about accelerated cartilage degeneration, although the latter is less definitively established for the subtalar joint than for larger weight-bearing joints like the knee or hip. Healthcare providers typically limit the number of injections within a specific timeframe to mitigate these risks.

When to Seek Medical Attention

It is crucial to contact your healthcare provider immediately if you experience any of the following after a subtalar joint injection:

• Signs of Infection: Increasing pain, redness, swelling, warmth at the injection site, especially if accompanied by fever or chills.
• Severe Allergic Reaction: Difficulty breathing, widespread rash, hives, swelling of the face or throat.
• New or Worsening Neurological Symptoms: Persistent numbness, tingling, or weakness in the foot or ankle that was not present before the injection or worsens significantly.
• Unmanageable Pain: Pain that is severe, not relieved by standard pain medications or ice, and significantly worse than the expected "steroid flare."
• Significant Bleeding: Excessive bleeding or a rapidly expanding bruise at the injection site.

Conclusion

Subtalar joint injections can be a valuable tool in the management of foot and ankle pain, offering significant relief for many individuals. While generally safe, it is important to be aware of the potential side effects, ranging from common, mild, and temporary discomforts to rare but serious complications like infection or nerve damage. A thorough discussion with your healthcare provider about the risks and benefits, as well as adherence to post-injection instructions, will help ensure the safest and most effective outcome. Always report any concerning symptoms promptly.