What are the treatment options for knee pain with extension and effusion?

Treatment of Knee Pain with Extension and Effusion

For knee pain with extension and effusion, start with oral paracetamol (acetaminophen) up to 4g/day, and if unresponsive, add NSAIDs (oral or topical); for acute exacerbation with effusion, intra-articular corticosteroid injection is indicated and provides superior short-term relief. 1, 2

Initial Diagnostic Approach

• Obtain radiographs including AP, lateral, sunrise/Merchant, and tunnel views to evaluate for structural pathology, effusion, and rule out fracture, degenerative changes, or osteochondral defects 1, 3
• If radiographs are normal or show only effusion but pain persists, MRI without IV contrast is the next indicated examination to evaluate menisci, articular cartilage, synovitis, bone marrow lesions, and subchondral insufficiency fractures 1
• Consider joint aspiration under ultrasound or fluoroscopic guidance if infection or crystal disease is suspected, though aspiration provides only temporary clinical relief (lasting approximately one week) due to early re-accumulation 1, 2, 4

Pharmacological Management Algorithm

First-Line Treatment

• Paracetamol (acetaminophen) 4g/day is the oral analgesic to try first and is the preferred long-term oral analgesic if successful 1, 2
• Paracetamol can be used effectively in doses up to 2400mg over 2 years without significant adverse effects 1
• This provides safe pain control with minimal contraindications, including safe use in elderly patients 1

Second-Line Treatment

• NSAIDs (oral or topical) should be considered in patients with effusion unresponsive to paracetamol 1, 2
• Oral NSAIDs demonstrate efficacy with effect size median of 0.49 compared to placebo 1, 2
• Topical NSAIDs (such as diclofenac) are useful alternatives in patients unwilling or unable to take oral NSAIDs, with effect size of 0.91 compared to placebo 1
• NSAIDs are more efficacious than paracetamol but carry increased gastrointestinal side effects 1

Important caveat: While NSAIDs are more effective than paracetamol, the specific recommendation to use them after paracetamol failure in effusion patients is based on expert consensus rather than direct comparative evidence 1

Intra-articular Corticosteroid Injection

• Intra-articular injection of long-acting steroid is indicated for acute exacerbation of knee pain, especially if accompanied by effusion 1, 2
• Corticosteroid injection is more effective than placebo for pain relief over 7 days (effect size 1.27) 1
• Significant differences between steroid and placebo persist after one week but not after 24 weeks, indicating relatively short-term benefit (1-12 weeks) 1, 2
• Better outcomes are observed in patients with effusion present 1
• For diabetic patients, monitor glucose levels for 1-3 days after injection due to potential transient hyperglycemia 2
• Avoid overuse of the injected joint for 24 hours following injection 2

Non-Pharmacological Management (Concurrent with Pharmacological)

• Optimal management requires combination of pharmacological and non-pharmacological treatment modalities 1
• Implement regular patient education about the condition and management 1, 2
• Exercises directed toward increasing quadriceps strength and/or preserving normal knee mobility are strongly recommended 1, 2
• Weight reduction if patient is overweight 1, 2
• Consider appliances such as walking sticks, insoles, or knee bracing 1, 2

Important note: Preoperative progressive resistance training does not exacerbate knee joint pain or effusion, despite concerns, and can increase muscle strength 5

Refractory Cases

• For persistent effusion and pain despite conservative measures, repeat intra-articular corticosteroid injection may be considered if previous injection provided relief 2
• Hyaluronic acid injections may be considered, though effect size is relatively small and suitable patients are not well defined 1, 2
• Avoid both corticosteroid and hyaluronic acid injections within 3 months prior to knee replacement surgery due to increased infection risk 2
• Joint replacement should be considered for refractory pain associated with disability and radiological deterioration 1, 2

Clinical Pitfalls

• Effusion presence alters knee mechanics and muscle activation patterns during gait, with increased quadriceps activation and prolonged hamstring activation 6
• Aspiration provides only temporary improvement lasting approximately one week due to early re-accumulation of effusion 4
• Meniscal tears are often incidental findings in older patients, with the majority of people over 70 years having asymptomatic meniscal tears 1
• Bone marrow lesions and synovitis/effusion on MRI may indicate the origin of knee pain in osteoarthritis patients 1