Intra-articular corticosteroid injections in the hip and knee: perhaps not as safe as we thought?

Key points

1. 018% of 459 IACS injections at one institution were followed by an adverse joint event on imaging (36 out of 459 patients)
2. 02Accelerated OA progression (RPOA type 1) was the most common adverse finding, occurring after 6% of injections
3. 03Subchondral insufficiency fracture, osteonecrosis complications, and rapid joint destruction (RPOA type 2) each occurred in under 1% of cases
4. 04Hip joints accounted for the majority of adverse events (30 of 36); knee joints accounted for 6 of 36
5. 05No large prospective studies or RCTs with long-term follow-up currently exist to confirm or quantify these risks

How it was conducted

Design

Retrospective observational case series and structured literature review (special report)

Institution

Single urban city hospital, Boston University School of Medicine

Participants

459 patients who received hip or knee IACS injections in 2018; 241 had postprocedural imaging available for analysis

Injection protocol

40 mg triamcinolone + 2 mL 1% lidocaine + 2 mL 0.25% bupivacaine, all US-guided

Follow-up

Mean 7 months between injection and imaging documentation of adverse event (range 2-15 months)

Primary outcome

Presence and type of adverse joint events on radiography or MRI after IACS injection

What they found

• 36 adverse joint events occurred in 36 of 459 patients (8%) who received IACS injections
• Accelerated OA progression (RPOA type 1): 26 events total - 21 hip (7%), 5 knee (3%), overall 6%
• Subchondral insufficiency fracture: 4 events total - 4 knee (0.9%)
• Osteonecrosis complications: 3 events total - 3 hip (1%), overall 0.7%
• Rapid joint destruction with bone loss (RPOA type 2): 3 events total - 2 hip (0.7%), 1 knee (0.7%), overall 0.7%
• Affected patients were 37-79 years old (mean age 57 years) and received 1-3 injections (mean 1.4 injections)
• 72% of affected patients had Kellgren-Lawrence grade 3 (moderate) OA preprocedurally
• Hip joints had more adverse events than knees: 30 of 36 events (10% of hip injections vs 4% of knee injections)
• 218 of 459 patients had no follow-up imaging or proceeded directly to joint replacement, limiting the denominator accuracy

Limitations

• Retrospective single-institution design with no control group, preventing causal inference - it is unknown whether observed adverse events were caused by or pre-dated the injection
• 218 of 459 patients lacked postprocedural imaging, meaning the true adverse event rate could be higher or lower than 8%
• No standardized follow-up imaging protocol; patients returned mainly due to worsening symptoms, introducing significant ascertainment bias
• The study cannot distinguish between adverse events caused by corticosteroids, local anesthetics (known chondrotoxins), or natural OA progression

Why it matters

For patients

Patients considering corticosteroid injections for hip or knee pain should discuss the possibility of serious joint complications - including accelerated joint destruction - with their doctor, particularly if they have moderate OA, subchondral bone problems, or osteonecrosis.

For clinicians

Clinicians should obtain a recent radiograph before each IACS injection, maintain a low threshold for pre-injection MRI when pain is unexplained by plain films or OA is mild, and consider adding these adverse joint risks explicitly to the informed consent process.

For readers

This report raises important safety signals about a very common procedure, but its retrospective single-centre design and lack of a control group mean the absolute risk attributable to IACS injection specifically remains unquantified pending larger prospective studies.