How should I evaluate and manage a patient with left knee pain?

Evaluation and Management of Left Knee Pain

Initial Diagnostic Approach

Begin with plain radiographs of the knee as your first imaging study—this is the single most appropriate initial test for chronic knee pain in patients ≥5 years of age. 1

History Taking

Obtain a systematic history covering these specific elements:

• Pain characteristics: onset (acute vs. insidious), quality, intensity, distribution, duration, and temporal course to differentiate ligamentous, meniscal, and patellofemoral pathology 2
• Mechanical symptoms: locking (true vs. pseudo-locking), popping, giving way, or catching 3, 4
• Effusion pattern: timing after activity, amount, and recurrence 5
• Mechanism of injury: twisting injury suggests meniscal tear in patients <40 years; degenerative tears occur in patients ≥40 years with osteoarthritis 3
• Functional impact: activities of daily living limitations, occupation effects, mood, relationships, and leisure activities 1, 2
• Prior treatments: document all diagnostic tests, therapies tried, current medications, and substance use 2

Physical Examination

Conduct a structured examination in this sequence:

Gait observation: Look for antalgic patterns, inability to bear weight, or compensatory movements 2

Inspection and palpation:

• Isolated patellar tenderness mandates radiography per Ottawa Knee Rules 2
• Tibial tubercle tenderness in adolescents suggests Osgood-Schlatter disease 2
• Fibular head tenderness requires radiography 2
• Joint line tenderness has 83% sensitivity and 83% specificity for meniscal tears 3

Range of motion: Normal knee flexion is 0°–135°; inability to flex beyond 90° warrants radiographic assessment 2

Patellofemoral assessment:

• Perform a decline-squat test (single-leg squat on decline)—this is 91% sensitive for patellofemoral pain syndrome 2
• Anterior knee pain during squatting is 91% sensitive and 50% specific for patellofemoral pain 3

Meniscal testing: McMurray test (concurrent knee rotation and extension) has 61% sensitivity and 84% specificity 3

Critical pitfall: Always examine the hip joint with range-of-motion testing, as hip pathology commonly refers pain to the knee 2, 6, 7. Also evaluate the lumbar spine for radiculopathy that can mimic knee pain 2, 7.

Imaging Strategy

Plain radiographs first: Order knee radiographs if the patient meets Ottawa Knee Rules criteria (age ≥55 years, isolated patellar tenderness, fibular head tenderness, inability to flex to 90°, or inability to bear weight) 1, 2

Common pitfall: Approximately 20% of patients receive inappropriate early MRI without obtaining plain radiographs first—avoid this error 2, 6

MRI indications: Order MRI without contrast when:

• Radiographs are normal or show only effusion but pain persists with mechanical symptoms suggesting meniscal or ligamentous injury 1, 6
• Chronic knee pain lasting ≥6 weeks with mechanical clicking and effusion to identify repairable meniscal tears 2
• You are considering surgical intervention 1

Important caveat: In patients >70 years, meniscal tears are often incidental findings, as the majority have asymptomatic tears 6, 7

Management Based on Diagnosis

If Osteoarthritis is Confirmed

Core non-pharmacological treatments (provide to ALL patients):

• Exercise therapy: Initiate structured physical therapy with quadriceps strengthening exercises immediately—this is the foundation of treatment 1, 6, 3
• Weight loss: Strongly recommended if BMI is elevated; aim for clinically meaningful reduction (e.g., BMI 33→28) 1, 6
• Patient education: Provide information to counter the misconception that osteoarthritis is inevitably progressive and untreatable 1
• Assistive devices: Consider a cane for the contralateral hand for longer walking distances 6

Pharmacological treatment algorithm:

1. First-line: Paracetamol (acetaminophen) up to 3 grams daily in divided doses—this is the preferred long-term oral analgesic if successful 1, 6

2. Second-line: If paracetamol insufficient, add topical NSAIDs before oral NSAIDs for knee osteoarthritis 1

3. Third-line: If still inadequate, consider:

   • Intra-articular corticosteroid injection for moderate to severe pain or acute exacerbation with effusion—provides approximately 2 months of relief and is preferred over hyaluronic acid 1, 6. Ultrasound guidance is not required for knee injections 6
   • Oral NSAIDs or COX-2 inhibitors at the lowest effective dose for the shortest duration, always with a proton pump inhibitor 1
   • Duloxetine as a centrally acting agent if NSAIDs provide inadequate relief 6

4. Opioids: Consider only if above measures fail, as adjunctive or substitute therapy 1

Important safety consideration: All oral NSAIDs and COX-2 inhibitors have similar analgesic effects but vary in gastrointestinal, liver, and cardiorenal toxicity—assess individual risk factors including age 1

Adjunct therapies to consider:

• Local heat or cold applications 1
• Bracing, joint supports, or insoles for biomechanical joint pain or instability 1
• TENS (transcutaneous electrical nerve stimulation) 1
• Shock-absorbing footwear 1

Do NOT use: Glucosamine, chondroitin, or electroacupuncture—these are not recommended 1

If Patellofemoral Pain Syndrome

• Hip and knee strengthening exercises combined with foot orthoses or patellar taping 3
• No indication for surgery 3

If Meniscal Tear

Conservative management first: Exercise therapy for 4–6 weeks is appropriate for most meniscal tears, including those with mechanical symptoms 3

Surgery indications: Reserve for severe traumatic tears (e.g., bucket-handle tears with displaced meniscal tissue) 3. For degenerative meniscal tears, exercise therapy is first-line; surgery is not indicated even with mechanical symptoms 3

Surgical Referral for Osteoarthritis

Consider joint replacement when:

• End-stage disease (minimal or no joint space) with inability to cope with pain 3
• Joint symptoms substantially impact quality of life despite optimal conservative treatment 1
• Patient has been offered at least the core treatment options first 1

Do NOT refer for: Arthroscopic lavage and debridement unless there is a clear history of true mechanical locking (not gelling, giving way, or radiographic loose bodies) 1

Key Clinical Pitfalls to Avoid

• Do not order MRI before plain radiographs 2, 6
• Do not attribute knee pain solely to local pathology without examining the hip and lumbar spine 2, 6, 7
• Do not rush to imaging before completing a thorough clinical examination, as most knee pain diagnoses can be made clinically 7
• Remember that bilateral structural abnormalities on imaging may not correlate with unilateral symptoms, particularly in patients >70 years 7