What is the initial workup and treatment for a patient presenting with knee pain?

Initial Workup for Knee Pain

Begin with plain radiographs (AP, lateral, tunnel/Rosenberg, and tangential patellar views) as the first-line imaging for any patient presenting with knee pain, regardless of whether the pain is acute or chronic. 1

Clinical History - Key Elements to Elicit

• Age: Patients ≥45 years with activity-related pain and <30 minutes of morning stiffness have 95% sensitivity for osteoarthritis 2
• Pain location: Anterior knee pain during squatting is 91% sensitive for patellofemoral pain syndrome (typically affects patients <40 years) 2
• Mechanism: Twisting injury suggests meniscal tear in younger patients; degenerative tears occur in patients ≥40 years with OA 2
• Mechanical symptoms: Locking, catching, popping, or giving way may indicate meniscal pathology or loose bodies 1
• Swelling and effusion: Presence and timing relative to injury 3
• Red flags: Fever, erythema, severe swelling with inability to bear weight require urgent evaluation for infection or fracture 3

Physical Examination - Systematic Approach

• Inspection: Swelling, erythema, deformity, muscle atrophy 3
• Palpation: Joint line tenderness (83% sensitive and 83% specific for meniscal tears), patellar tenderness, fibular head tenderness 2, 1
• Range of motion: Inability to flex to 90° warrants radiographs per Ottawa Knee Rule 1
• McMurray test: Knee rotation with extension (61% sensitive, 84% specific for meniscal tears) 2
• Weight-bearing status: Inability to take 4 weight-bearing steps requires imaging 1
• Consider referred pain: Examine hip and lumbar spine if knee radiographs are unremarkable 1

Initial Imaging Algorithm

Radiographs are indicated if any of the following criteria are met (Ottawa Knee Rule for acute trauma, age-based for chronic pain) 1:

• Age ≥55 years (acute trauma) or ≥45 years (chronic pain) 1, 2
• Isolated patellar tenderness 1
• Fibular head tenderness 1
• Cannot flex knee to 90° 1
• Cannot bear weight immediately after injury or take 4 steps in clinic 1

For chronic knee pain (>6 weeks duration): Radiographs should be obtained before considering MRI, as approximately 20% of patients inappropriately receive MRI without recent radiographs 1

Advanced Imaging - When to Proceed

MRI without contrast is indicated when 1:

• Radiographs are normal or show only joint effusion, but pain persists despite conservative treatment 1
• Radiographs demonstrate osteochondritis dissecans, loose bodies, or prior cartilage/meniscal repair requiring characterization 1
• Clinical suspicion for meniscal tear, ligament injury, or occult fracture in appropriate clinical context 1

Important caveat: Meniscal tears are incidental findings in the majority of patients >70 years and are equally common in painful and asymptomatic knees in patients 45-55 years 1

Initial Treatment Strategy

Non-Pharmacologic (Strongly Recommended First-Line) 1

• Exercise therapy: Land-based cardiovascular and/or resistance training (strong recommendation) 1
• Aquatic exercise (strong recommendation) 1
• Weight loss: For all overweight patients (strong recommendation) 1
• Self-management programs and patient education 1

Pharmacologic Options 1, 4

Initial therapy - choose one of the following (conditional recommendations, no strong preference) 1:

• Acetaminophen: Up to 4,000 mg/day; counsel patients to avoid other acetaminophen-containing products 1
• Topical NSAIDs: Preferred over oral NSAIDs in patients ≥75 years (strong recommendation for this age group) 1
• Oral NSAIDs: Ibuprofen 400 mg every 4-6 hours (up to 3,200 mg/day for inflammatory arthritis, though 400 mg doses are equally effective for pain) 1, 4
• Tramadol 1
• Intra-articular corticosteroid injections 1

If inadequate response to acetaminophen: Strongly recommend oral or topical NSAIDs or intra-articular corticosteroid injections 1

Do NOT use (conditional recommendation against) 1:

• Glucosamine or chondroitin sulfate 1
• Topical capsaicin 1

NSAID Safety Considerations 1

• Patients ≥75 years: Use topical rather than oral NSAIDs (strong recommendation) 1
• History of complicated GI ulcer without recent bleed: Use COX-2 selective inhibitor OR nonselective NSAID plus proton-pump inhibitor 1
• GI bleed within past year: Use COX-2 selective inhibitor PLUS proton-pump inhibitor if oral NSAID chosen 1

Urgent Referral Criteria 3

Immediate orthopedic consultation required for:

• Severe pain, swelling, and instability with inability to bear weight after acute trauma 3
• Signs of septic arthritis: fever, erythema, warmth, severe swelling, limited range of motion 3
• Suspected fracture or dislocation 3

When Conservative Management Fails

• For OA: Consider surgical referral for joint replacement only after exhausting all conservative options in patients with end-stage disease (minimal/no joint space with inability to cope with pain) 2
• For patellofemoral pain: Surgery is NOT indicated; continue conservative management with hip/knee strengthening, foot orthoses, or patellar taping 2
• For meniscal tears: Exercise therapy for 4-6 weeks is first-line; surgery only for severe traumatic bucket-handle tears with displaced tissue, NOT for degenerative tears even with mechanical symptoms 2