What is the recommended treatment for knee effusion?

Treatment of Knee Effusion

Intra-articular corticosteroid injection is the first-line treatment for knee effusion, particularly when accompanied by acute pain or inflammatory signs, providing significant relief within 1-2 weeks. 1, 2

Initial Assessment and Treatment Algorithm

The presence of effusion should guide your treatment approach, as corticosteroid injections demonstrate superior efficacy when effusion is present compared to when it is absent 3, 1. Patients with effusion at baseline respond better to intra-articular corticosteroids than those without effusion 3, 2.

First-Line Treatment: Intra-Articular Corticosteroid

• Inject long-acting corticosteroid directly into the joint for acute effusion with pain, especially when inflammatory signs are present 1, 2
• Expect pain relief within 1-2 weeks, with significant differences between steroid and placebo lasting through 4 weeks 3, 1
• Benefits typically persist for 1-12 weeks, though this is shorter-lived than some alternatives 3, 1, 2
• In diabetic patients, monitor glucose levels for 1-3 days post-injection due to transient hyperglycemia risk 1
• Advise patients to avoid overuse of the injected joint for 24 hours following injection 1

Concurrent Pharmacological Management

While corticosteroid injection addresses the effusion directly, oral medications provide additional symptomatic relief:

• Start oral acetaminophen (paracetamol) up to 4,000 mg/day as initial analgesic for mild to moderate pain, which is safe for long-term use 1, 2
• Add NSAIDs (oral or topical) if acetaminophen is insufficient, particularly in patients with persistent effusion, as they demonstrate efficacy with effect size of 0.49 1, 2
• Prefer topical NSAIDs in patients ≥75 years old due to better safety profile 4

Essential Non-Pharmacological Interventions

These should be implemented concurrently, not sequentially, with pharmacological treatment:

• Prescribe quadriceps strengthening exercises to preserve normal knee mobility 4, 1, 2
• Recommend weight reduction for overweight patients to reduce joint pressure 4, 1, 2
• Provide regular patient education about the condition and self-management strategies 1, 2
• Consider physical supports such as walking sticks, insoles, or knee bracing to offload the joint 4, 1, 2

Management of Persistent or Recurrent Effusion

When initial treatment fails or effusion recurs:

• Repeat intra-articular corticosteroid injection if the previous injection provided relief 1
• Consider hyaluronic acid injections as a second-line option, though effect sizes are relatively small (0.04-0.9) and require 3-5 weekly injections 3, 1, 2
• Hyaluronic acid may provide longer duration of benefit (several months versus several weeks with steroids), but this is offset by slower onset of action 3
• Avoid both corticosteroid and hyaluronic acid injections within 3 months prior to knee replacement surgery due to increased infection risk 1

Role of Aspiration

Aspiration provides only temporary improvement lasting approximately one week due to early re-accumulation of fluid 5. However, aspiration is valuable in specific circumstances:

• Perform aspiration in effusions of unknown etiology to establish diagnosis through synovial fluid analysis 5, 6
• Consider aspiration for immediate clinical relief in severe effusion, recognizing the benefit is short-lived 5
• Exercise caution with aspiration in traumatic effusions, as the benefit is minimal and temporary 5

Refractory Cases Requiring Surgical Consideration

Joint replacement should be considered for patients with refractory pain, disability, and radiographic evidence of structural deterioration despite conservative measures 3, 1, 2. Total knee replacement demonstrates effectiveness in improving quality of life, reducing pain, and improving function in severely incapacitated patients 3.

Critical Pitfalls to Avoid

• Do not reserve corticosteroid injection only for patients with effusion—while effusion predicts better response, patients without visible effusion may still benefit 3
• Do not rely on aspiration alone as definitive treatment—it provides only temporary relief and effusion typically recurs within one week 5
• Patients with more severe structural disease and those with baseline effusion respond worse to hyaluronic acid, so consider disease severity when selecting this option 3
• Most trials of hyaluronic acid exclude severe osteoarthritis, limiting evidence for its use in advanced disease 3