Injectable Treatments for Knee Osteoarthritis
Intra-articular corticosteroid injections are the only injectable treatment with strong evidence-based support for knee osteoarthritis, while hyaluronic acid injections are explicitly not recommended by major guidelines. 1, 2
Primary Recommendation: Corticosteroid Injections
Intra-articular corticosteroid injections should be used for acute flares of knee pain, particularly when accompanied by joint effusion. 1, 2
- The AAOS provides Level 1B evidence supporting corticosteroid injections, based on 19 high-quality and 6 moderate-quality studies 2
- Corticosteroids provide effective short-term pain relief lasting up to 3 weeks through anti-inflammatory and antinociceptive mechanisms 3
- These injections are most appropriate for symptom flares and can be repeated as needed for recurrent symptoms 2
- The typical dose is 5-15 mg for larger joints like the knee, with doses up to 40 mg used for larger areas 4
Explicitly Not Recommended: Hyaluronic Acid
Hyaluronic acid injections should not be used for knee osteoarthritis based on current evidence. 1, 5, 2
- The AAOS conditionally recommends against routine use of hyaluronic acid, citing inconsistent evidence across 17 high-quality and 11 moderate-quality studies 2
- The number needed to treat is 17 patients, meaning 16 patients receive no benefit for every 1 patient who does 5, 2
- The ACR/Arthritis Foundation conditionally recommends against hyaluronic acid injections, noting that high-quality trials with low risk of bias show effect sizes approaching zero 5, 2
- Hyaluronic acid should not be used as "bridge therapy" when patients have already failed appropriate conservative management 2
Insufficient Evidence: Platelet-Rich Plasma
PRP injections cannot be recommended due to insufficient evidence, despite some promising preliminary data. 5, 6
- Current guidelines conclude that PRP lacks sufficient evidence to definitively recommend for or against use 6
- PRP is not recommended for severe osteoarthritis due to inconsistent results and potential for worse outcomes 5
- While some research suggests PRP may provide benefit in younger patients with mild OA, this has not translated into guideline-level recommendations 7, 6
Treatment Algorithm Before Considering Injectables
Before any injectable therapy, patients must fail appropriate conservative management:
- First-line therapies: Land-based exercise programs, strengthening exercises, low-impact aerobic activity, and neuromuscular education 1, 2
- Weight reduction: For patients with BMI ≥25 kg/m², weight loss should be pursued 1
- Oral medications: Acetaminophen up to 3g daily in divided doses, oral or topical NSAIDs 1, 2
- Physical therapy: Structured physical therapy programs with specific strengthening protocols 2
When to Consider Surgical Referral
Total knee arthroplasty should be considered for patients with severe pain limiting ambulation and daily activities who have failed conservative management including corticosteroid injections. 5
- Joint replacement is indicated for refractory pain with disability and radiological deterioration when conservative management has failed 1, 5
- Patients with severe bilateral knee pain, significant functional limitations, and failed conservative treatments warrant surgical referral 5
Critical Pitfalls to Avoid
- Never use arthroscopic debridement or partial meniscectomy for primary osteoarthritis, as it provides no benefit over conservative management and delays definitive treatment 5, 2
- Avoid oral narcotics for knee osteoarthritis due to notable increase in adverse effects with no consistent improvement in pain and function 2
- Do not delay surgical referral in appropriate candidates by pursuing ineffective injectable therapies like hyaluronic acid 2
- Ensure proper injection technique for corticosteroids by injecting deeply into the joint space, not surrounding tissues, to avoid tissue atrophy 4