What is the recommended treatment for an adult patient with knee pain likely due to osteoarthritis, considering potential gastrointestinal issues, cardiovascular disease, or anticoagulant use, using diclofenac (NSAID) gel?

Diclofenac Gel for Knee Osteoarthritis

Topical diclofenac gel is a highly recommended first-line pharmacologic treatment for knee osteoarthritis, offering effective pain relief with markedly reduced systemic toxicity compared to oral NSAIDs, making it particularly valuable for patients with gastrointestinal issues, cardiovascular disease, or anticoagulant use. 1

Treatment Algorithm

Step 1: Core Non-Pharmacologic Treatments (Essential Foundation)

Before or alongside any medication, ensure the patient engages in:

• Self-management programs, strengthening exercises, low-impact aerobic exercise, and neuromuscular education 2
• Weight loss if BMI ≥25 kg/m² 2
• Local heat/cold applications and assistive devices 2

Step 2: First-Line Pharmacologic Treatment

Apply topical diclofenac gel before considering oral NSAIDs:

• Dosing: Apply 2 pump actuations (40 mg diclofenac sodium) to each painful knee, twice daily 3
• Apply to clean, dry skin; spread evenly around front, back, and sides of the knee 3
• Wash hands completely after application 3
• Avoid showering/bathing for at least 30 minutes after application 3
• Wait until area is completely dry before covering with clothing 3

Why topical first:

• Minimal systemic absorption avoids gastrointestinal, cardiovascular, renal, and hepatic toxicity that is particularly problematic in elderly patients with comorbidities 1
• Demonstrated significant pain reduction and functional improvement in randomized controlled trials, with WOMAC pain scores improving by 3.9 points versus 2.5 points for placebo (p=0.016) 4
• Pooled safety data extending to 12 weeks shows similar low rates of adverse effects in high-risk patients (age ≥65 years, hypertension, diabetes, cardiovascular disease) compared to low-risk patients 1

Step 3: If Topical Diclofenac Provides Insufficient Relief After 4 Weeks

Only then consider adding (not substituting) oral NSAIDs or COX-2 inhibitors: 1

• Use at the lowest effective dose for the shortest possible duration 2
• Always co-prescribe a proton pump inhibitor for gastroprotection, choosing the one with lowest acquisition cost 2, 5
• Carefully assess cardiovascular, gastrointestinal, and renal risk factors before prescribing 5

Critical Safety Advantages for High-Risk Patients

Gastrointestinal Issues

• Topical diclofenac avoids the substantial GI bleeding risk associated with oral NSAIDs 1
• No serious gastrointestinal adverse events were reported in clinical trials of topical diclofenac 4, 6
• The most common adverse effect is minor local skin irritation (dryness in 36.6%, rash in 11.0%), which is self-limiting 6

Cardiovascular Disease

• Markedly reduced systemic exposure eliminates the cardiovascular risks (hypertension exacerbation, fluid retention, increased thrombotic events) associated with oral NSAIDs 1
• Particularly important for elderly patients who face substantially higher cardiovascular complications with oral NSAIDs 7

Anticoagulant Use

• Minimal systemic absorption means negligible platelet dysfunction risk compared to oral NSAIDs 7
• Topical formulation is an acceptable alternative in patients requiring anticoagulation 1

Renal Impairment

• Topical NSAIDs are acceptable alternatives with minimal systemic absorption in patients with renal impairment, whereas oral NSAIDs are contraindicated or require extreme caution 7

Expected Clinical Outcomes

Efficacy demonstrated in multiple randomized controlled trials:

• 12-week trial showed DSG provided 52.6% reduction in WOMAC pain versus 43.1% for vehicle (p=0.008) and 49.7% reduction in physical function versus 39.4% for vehicle (p=0.004) 8
• Significant improvements in stiffness, pain on walking, and patient global assessment 4, 6
• Benefits observed irrespective of disease severity (Kellgren-Lawrence grades 1-3) or patient age 8

Common Pitfalls to Avoid

• Do not combine topical diclofenac with oral NSAIDs unless the benefit outweighs the risk, and conduct periodic laboratory evaluations if combination therapy is necessary 3
• Do not apply to open wounds or use with occlusive dressings or external heat 3
• Protect treated knee from natural and artificial sunlight; wait until area is dry before applying sunscreen 3
• Avoid skin-to-skin contact between other people and the treated knee until completely dry 3
• Do not exceed recommended dosing (2 pump actuations per knee, twice daily); higher or lower doses have not been studied 3

Treatments NOT Recommended

Strong evidence against the following for knee osteoarthritis:

• Acupuncture, glucosamine, and chondroitin are not recommended due to lack of clinically important outcomes compared to placebo 2
• Hyaluronic acid injections are not recommended 2
• Lateral wedge insoles are not suggested 2