What is the appropriate workup for a patient with knee pain before considering a cortisone (corticosteroid) injection, taking into account their age, medical history, and lifestyle?

Workup for Knee Pain Before Cortisone Injection

Begin with plain radiographs of the knee (standing AP, lateral, and sunrise views) to assess for osteoarthritis, loose bodies, or structural abnormalities, and perform joint aspiration if an effusion is present to rule out infection or crystal disease before proceeding with corticosteroid injection. 1

Essential Initial Imaging

• Plain radiographs are the first-line imaging modality for all patients with chronic knee pain being considered for corticosteroid injection 1
• Standing anteroposterior, lateral, and sunrise (patellofemoral) views should be obtained to evaluate for:
  • Osteoarthritis severity (Kellgren-Lawrence grading)
  • Joint space narrowing
  • Osteophyte formation
  • Loose bodies
  • Prior osseous injury 1

Critical Pre-Injection Assessment: Rule Out Infection and Crystal Disease

• If an effusion is present on examination, joint aspiration must be performed before corticosteroid injection to analyze synovial fluid for:
  • Cell count and differential (to exclude septic arthritis)
  • Crystal analysis (to identify gout or pseudogout)
  • Gram stain and culture if infection is suspected 1
• This step is non-negotiable, as injecting corticosteroids into an infected joint can lead to catastrophic outcomes 1

When Advanced Imaging Is Indicated

MRI is NOT routinely required before corticosteroid injection but should be obtained in specific circumstances: 1

• Radiographs show findings suggesting meniscal pathology, ligamentous injury, or osteochondral defects that might change management
• Clinical examination suggests internal derangement (locking, catching, giving way) that may require surgical intervention rather than injection
• Pain persists despite appropriate conservative treatment and injection, to evaluate for occult pathology 1

Ultrasound has limited utility as a screening tool but can be used to:

• Detect synovial pathology and effusions
• Guide aspiration if needed
• Demonstrate meniscal extrusion or chondrocalcinosis 1

Age-Specific Considerations

• In patients >70 years old, bilateral structural abnormalities on radiographs or MRI are common even with unilateral symptoms, making it difficult to discriminate painful from non-painful knees based on imaging alone 1
• The presence of synovitis, effusion, or Kellgren-Lawrence score ≥2 are the best discriminators between painful and asymptomatic knees in this age group 1

Pre-Injection Medical History Requirements

Document the following before proceeding with injection: 1

• Medication history, particularly:
  • Anticoagulation status (warfarin, DOACs, antiplatelet agents)
  • Current NSAID use and response
  • Prior corticosteroid injections (timing, response, number)
  • All over-the-counter medications 1
• Diabetes status: Patients must be counseled that corticosteroids can cause transient hyperglycemia for 1-3 days post-injection 2
• Upcoming surgical plans: Corticosteroid injection should be avoided within 3 months of planned knee replacement surgery due to theoretical infection risk 1, 2, 3
• History of prior injections: Multiple corticosteroid injections (≥3) are associated with dose-dependent risk of progression to total knee arthroplasty, with time to TKA nearly halved after three injections compared to one 4

Conservative Treatment Documentation

Before offering corticosteroid injection, document trial of: 1

• Acetaminophen (up to 4 grams daily, lowest effective dose due to hepatotoxicity risk) 1
• Topical NSAIDs or counterirritants (capsaicin, menthol) for mild-to-moderate pain 1
• Physical therapy or structured exercise program 1

Corticosteroid injection is particularly indicated when: 1

• Evidence of acute inflammation with joint effusion is present
• Systemic NSAIDs are contraindicated (GI bleeding history, renal insufficiency, heart failure, elderly patients at high risk for NSAID complications) 1
• Pain is refractory to non-invasive pharmacologic and non-pharmacologic therapies 1

Common Pitfalls to Avoid

• Do not inject without ruling out infection if effusion is present—this is the most critical safety consideration 1
• Do not order MRI routinely—it is not indicated before injection unless specific clinical findings suggest internal derangement that would change management 1
• Do not inject within 3 months of planned arthroplasty due to infection risk 1, 2, 3
• Do not repeat injections more frequently than every 3-4 months, as benefits typically last only 1-12 weeks (most benefit in first 3-4 weeks), and Medicare typically covers injections at 3-4 month intervals 5, 2, 3
• Be aware of dose-dependent risk: Three or more injections in non-osteoarthritic knees are associated with 3.22-fold increased odds of TKA at 5 years compared to no injection 4

Expected Outcomes and Counseling Points

• Pain relief is short-term only (1-12 weeks, typically 3-4 weeks), with no long-term improvement at 2-year follow-up 1, 5, 3
• Methylprednisolone improves pain and function at 4 and 24 weeks, while triamcinolone shows benefit at 6 weeks but not 12 weeks 1, 3
• Presence of effusion predicts better response to injection 5
• Patients should avoid overuse of the injected joint for 24 hours following injection 2