Does a steroid (corticosteroid) knee joint injection get absorbed systemically?

Systemic Absorption of Corticosteroid Knee Joint Injections

Yes, corticosteroid knee joint injections are systemically absorbed, with complete absorption typically occurring over a period of 2-3 weeks following injection. 1

Mechanism and Timeline of Systemic Absorption

Intra-articular corticosteroid injections are primarily intended for local anti-inflammatory effects, but significant systemic absorption does occur:

• Complete absorption from the injection site takes place over 2-3 weeks 1
• Systemic absorption varies based on the specific corticosteroid formulation:
  • Triamcinolone hexacetonide is absorbed more slowly than triamcinolone acetonide due to lower solubility 1
  • Extended-release formulations (like FX006) are designed to prolong joint residence time and reduce systemic exposure compared to standard crystalline suspensions 2

Measurable Systemic Effects

The systemic absorption of intra-articular corticosteroids produces several measurable effects:

1. Hypothalamic-pituitary-adrenal (HPA) axis suppression:

   • Serum cortisol decreases within hours after injection
   • Nadir typically occurs at 24-48 hours post-injection
   • Recovery to baseline takes 1-4 weeks (sometimes longer) 3
   • Duration depends on corticosteroid type, dose, and number of injected joints

2. Metabolic effects:

   • Transient increase in blood glucose levels in diabetic patients
   • Peak glucose levels can reach around 300 mg/dL 3
   • FDA labeling specifically warns about potential hyperglycemia 4

3. Inflammatory marker reduction:

   • Decreased C-reactive protein and erythrocyte sedimentation rate
   • Reduction begins days after injection and can last for months
   • Immediate decrease in inflammatory cytokines (within hours) 3

Clinical Implications and Risks

The systemic absorption of intra-articular corticosteroids has important clinical implications:

• Diabetic patients should be informed about the risk of transient increased glycemia following intra-articular glucocorticoids and advised to monitor glucose levels, particularly from the first to third day 5

• Potential systemic side effects include:

  • Cushing syndrome
  • Loss of bone density
  • Increased infection risk
  • Hyperglycemia 6

• Risk factors for increased systemic effects:

  • Concurrent use of oral steroids
  • Multiple injections
  • Type and dose of glucocorticoid used 6

Long-Term Safety Considerations

Despite systemic absorption, long-term safety data is generally reassuring:

• A randomized, double-blind, placebo-controlled trial over 2 years found no deleterious effects on knee joint structure with repeated triamcinolone acetonide injections every 3 months 7

• The EULAR recommendations acknowledge systemic absorption but support the use of intra-articular corticosteroids for acute exacerbation of knee pain, especially if accompanied by effusion 5

Clinical Recommendations

When administering corticosteroid knee injections, clinicians should:

1. Calculate total glucocorticoid exposure including all local injections 6

2. Exercise caution in high-risk patients:

   • Postmenopausal women (osteoporosis risk)
   • People with diabetes (hyperglycemia risk)
   • Patients considering surgery in the near term (infection risk) 6

3. Inform diabetic patients about the need to monitor glucose levels for several days after injection 5

4. Consider that intra-articular steroid injections provide relatively short-lived benefit (1-4 weeks) compared to other treatments 5

The FDA label for triamcinolone specifically states that "intra-articularly injected corticosteroids may be systemically absorbed," highlighting the importance of recognizing this phenomenon in clinical practice 4.