What are the initial management recommendations for a patient with knee osteoarthritis, considering their medical history and potential allergies or sensitivities to Nonsteroidal Anti-Inflammatory Drugs (NSAIDs)?

Initial Management of Knee Osteoarthritis

Start with acetaminophen (paracetamol) up to 4,000 mg/day as first-line pharmacologic therapy, combined with non-pharmacologic interventions including patient education, quadriceps-strengthening exercises, and weight loss if overweight. 1

First-Line Treatment Algorithm

Non-Pharmacologic Interventions (Initiate Immediately)

• Patient education programs should be implemented first, as they have strong evidence for improving pain and function 2
• Quadriceps-strengthening exercises are mandatory and should be prescribed early, focusing on both strength and preserving normal knee mobility 3, 2
• Weight reduction is essential for overweight/obese patients, as it reduces risk of disease progression and improves pain outcomes 3, 2
• Physical therapy referral for supervised exercise programs should occur early—delaying this referral is a critical pitfall that worsens outcomes 2
• Consider assistive devices (walking sticks, knee bracing, shoe insoles) as adjunctive measures 3

First-Line Pharmacologic Therapy

• Acetaminophen (paracetamol) 4,000 mg/day is the initial oral analgesic of choice due to its favorable safety profile compared to NSAIDs 1, 3
• The full dosage of 4,000 mg/day must be used before considering it ineffective—underdosing is a common error 1
• Counsel patients to avoid other acetaminophen-containing products to prevent exceeding maximum daily dose 1
• Acetaminophen has no common contraindications, making it safe even in elderly patients 3

For Patients with NSAID Allergies/Sensitivities

If the patient cannot tolerate NSAIDs or has contraindications (history of GI bleeding, cardiovascular disease, renal impairment):

• Topical NSAIDs are the preferred alternative, especially for patients ≥75 years old, as they avoid systemic adverse effects 1
• Tramadol is a conditionally recommended option when acetaminophen and topical NSAIDs cannot be used 1
• Intra-articular corticosteroid injections are indicated for acute pain exacerbations, particularly when accompanied by joint effusion 3, 1

Second-Line Therapy (When Acetaminophen Fails)

For Patients Who CAN Use NSAIDs

• Oral or topical NSAIDs are strongly recommended as second-line therapy for acetaminophen non-responders 1, 3
• For patients ≥75 years old, topical NSAIDs are strongly preferred over oral NSAIDs due to superior safety profile 1
• When oral NSAIDs are necessary in patients with GI risk factors (prior ulcer disease, concurrent corticosteroids/anticoagulants, smoking, alcohol use, older age), use either:
  • COX-2 selective inhibitor, OR
  • Non-selective NSAID plus proton-pump inhibitor 1, 4
• Use the lowest effective NSAID dose for the shortest duration possible 4, 5

For Patients Who CANNOT Use NSAIDs

• Continue acetaminophen at maximum dose 1
• Add intra-articular corticosteroid injections for flares with effusion 3, 1
• Consider tramadol, though evidence shows poor risk-benefit ratio 6
• Opioids may be considered for severe refractory pain, but require careful patient selection and monitoring due to adverse effects 6

Treatments NOT Recommended

• Glucosamine and chondroitin sulfate are conditionally NOT recommended due to lack of efficacy evidence 1
• Topical capsaicin is conditionally NOT recommended due to limited evidence and potential side effects 1

Critical Safety Considerations for NSAIDs

When NSAIDs must be used, monitor for:

• GI complications: Risk of ulceration, bleeding, and perforation occurs in 1% at 3-6 months and 2-4% at one year 4
• Cardiovascular events: Avoid in patients with history of cardiovascular disease 4
• Renal toxicity: Particularly high risk in elderly patients, those with pre-existing renal impairment, heart failure, liver dysfunction, or concurrent diuretic/ACE inhibitor use 4
• Pregnancy: Avoid NSAIDs after 20 weeks gestation due to risk of fetal renal dysfunction and premature ductus arteriosus closure 4

Common Pitfalls to Avoid

• Underdosing acetaminophen before declaring it ineffective—must use full 4,000 mg/day 1
• Delaying physical therapy referral—early exercise intervention is crucial for maintaining function 2
• Over-reliance on oral opioids without addressing non-pharmacologic interventions 2
• Failing to address weight management in overweight/obese patients 2
• Using NSAIDs without gastroprotection in high-risk patients 1, 4