What is the appropriate history, physical examination, work‑up, and initial management for a patient presenting with knee pain?

Knee Pain Assessment and Initial Management

Immediate History Components

Obtain age, pain location, onset/duration, mechanical symptoms (locking, clicking, giving way), swelling timing, and trauma mechanism—these direct your differential and imaging decisions. 1, 2, 3

Critical Historical Red Flags Requiring Urgent Evaluation

• Fever, erythema, warmth, and limited range of motion suggest septic arthritis and mandate immediate joint aspiration and culture 4
• Severe pain with inability to bear weight after acute trauma warrants urgent radiography to exclude fracture 2, 4
• Gross deformity, palpable mass, or penetrating injury requires immediate imaging regardless of other findings 2

Age-Stratified Differential Priorities

• Age ≥45 years with activity-related pain and <30 minutes morning stiffness: Osteoarthritis is most likely (95% sensitivity, 69% specificity) 5
• Age <40 years with anterior knee pain during squatting: Patellofemoral pain syndrome is most likely (91% sensitivity, 50% specificity) 5
• Middle-aged to elderly females with medial knee pain: Consider subchondral insufficiency fracture, often radiographically occult initially 6

Mechanical Symptom Interpretation

• Chronic clicking (≥3 months) with small effusion: Strongly suggests meniscal tear requiring MRI evaluation; delaying MRI risks progression from repairable to irreparable tear 1
• True locking (motion completely halted): Indicates displaced meniscal tissue (bucket-handle tear) or loose body requiring surgical referral 7, 1
• Giving way: May indicate ligamentous injury (ACL) or patellar instability depending on mechanism 8, 3

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Physical Examination Algorithm

Always examine the uninjured knee first for comparison, then systematically assess the injured knee through inspection, palpation, range of motion, ligament testing, and meniscal provocation. 8, 3

Inspection and Palpation Sequence

• Inspect for effusion, erythema, deformity, and muscle atrophy (particularly vastus medialis obliquus) 3, 9
• Palpate joint line tenderness: 83% sensitive and 83% specific for meniscal tears 5
• Palpate patella, tibial tubercle, and fibular head: Isolated tenderness at these sites increases fracture probability and imaging indication 2, 3
• Assess for crepitus in patellofemoral compartment: Suggests osteoarthritis or chondromalacia 9

Range of Motion Testing

• Active and passive flexion/extension: Inability to flex to 90° mandates radiography per Ottawa rules 2, 3
• Limited range of motion with end-range pain: Characteristic of osteoarthritis 9

Ligament Stability Testing

• Lachman test (most sensitive for ACL injury): Perform with knee at 20-30° flexion, assess anterior tibial translation 8
• Posterior drawer and tibial sag tests: Evaluate posterior cruciate ligament integrity 8
• Valgus and varus stress testing: Assess medial and lateral collateral ligament integrity 8

Meniscal Provocation Tests

• McMurray test: Concurrent knee rotation (internal for lateral meniscus, external for medial) with extension from flexion; 61% sensitive, 84% specific for meniscal tears 5
• Apley grind test and bounce test: Supplementary meniscal evaluation 8

Critical Pitfall: Exclude Referred Pain Sources

• Assess hip range of motion and inquire about groin pain: Hip pathology commonly refers to the knee; if hip symptoms present, obtain hip radiographs before knee MRI 1, 2
• Screen for lumbar radiculopathy: Back pain or radicular symptoms may mimic knee pain; assess for spinal symptoms 1, 6

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Initial Imaging Protocol

Plain radiographs (minimum AP and lateral views; ideally add tunnel and sunrise/Merchant views) are mandatory first-line imaging for all knee pain before considering advanced imaging. 7, 1, 2

Radiograph Indications (Ottawa Rules for Acute Trauma)

Obtain radiographs if any of the following:

• Age ≥55 years 2, 3
• Isolated patellar tenderness or fibular head tenderness 2, 3
• Inability to bear weight (4 steps) or flex knee to 90° 2, 3
• Gross deformity, palpable mass, or penetrating injury 2

Radiograph Indications for Chronic Pain (≥6 weeks)

• All patients with chronic knee pain require radiographs before MRI; approximately 20% inappropriately receive MRI without recent radiographs, which is a major quality gap 1, 2, 6
• Standard three-view series: (1) frontal projection (AP, Rosenberg, or tunnel), (2) tangential patellar (skyline) view, (3) lateral view 1, 2

When to Proceed to MRI After Normal Radiographs

Order non-contrast MRI when radiographs are normal or show only effusion AND pain persists ≥3 months with mechanical clicking—this combination strongly suggests internal derangement (meniscal tear, cartilage defect, or osteochondritis dissecans). 7, 1

MRI Diagnostic Targets

• Meniscal tears: 86-100% sensitivity; medial tears produce medial clicking, lateral tears produce lateral clicking 1
• Articular cartilage defects and early osteochondritis dissecans: May produce pain and effusion despite normal radiographs 7, 1, 6
• Ligament injuries (ACL, PCL, collaterals): Often occult on plain films 1
• Bone marrow edema: Strongly associated with pain, especially in males or patients with family history of osteoarthritis; not visible on radiographs 2, 6
• Synovial pathology (plicae, loose bodies, synovitis): Can cause clicking and effusion 1

Imaging Modalities NOT Recommended as First Choice

• Ultrasound: Insufficient for comprehensive meniscal or intra-articular evaluation; only confirms effusion and guides aspiration 1, 2
• CT/CT arthrography: Lower soft-tissue resolution than MRI; reserve for MRI contraindications 1
• MRI with IV contrast: Reserved for suspected infection, tumor, or inflammatory arthropathy—not indicated for isolated mechanical symptoms 1

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Laboratory Testing

Reserve laboratory tests for suspected inflammatory, infectious, or crystal arthropathy when history and examination suggest systemic or inflammatory etiology. 4

Indications for Joint Aspiration and Synovial Fluid Analysis

• Fever, erythema, warmth, and acute effusion: Obtain cell count with differential, Gram stain, culture, and crystal analysis to exclude septic arthritis or gout 4
• Chronic effusion without mechanical symptoms: Consider aspiration for crystal analysis if inflammatory arthritis suspected 1, 4

Common Pitfall

• Do not perform knee aspiration for small chronic effusion with mechanical symptoms; this combination indicates structural pathology requiring MRI, not aspiration 1

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Initial Management While Awaiting Imaging or Specialist Referral

Initiate conservative management immediately for non-urgent cases; definitive treatment will be guided by imaging findings. 1, 5

Activity Modification

• Avoid deep squatting, pivoting, or movements that provoke clicking or pain 1
• Maintain weight-bearing as tolerated unless severe pain or instability present 5

Pharmacologic Management

• NSAIDs: Provide symptomatic relief when not contraindicated 1, 5
• Acetaminophen: Alternative for patients with NSAID contraindications 5

Physical Therapy

• Initiate quadriceps strengthening and range-of-motion exercises for all patients 1, 5
• For suspected patellofemoral pain: Hip and knee strengthening exercises combined with foot orthoses or patellar taping 5
• For suspected osteoarthritis: Exercise therapy, weight loss if overweight, and self-management education are first-line treatments 5

Conservative Management Duration Before Surgical Consideration

• Most meniscal tears: 4-6 weeks of exercise therapy before considering surgery 5
• Degenerative meniscal tears: Surgery not indicated even with mechanical symptoms; exercise therapy is definitive treatment 5
• Bucket-handle tears with true locking: Immediate orthopedic referral; surgery likely required 5

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Post-Imaging Decision Pathway

MRI Findings Requiring Orthopedic Referral

• Repairable meniscal tear (especially in patients <40 years with acute trauma) 1, 5
• Loose body or displaced meniscal tissue 1
• Unstable osteochondritis dissecans (hyperintense rim or cysts at fragment periphery in adults) 7, 6
• Complete ligament tears (ACL, PCL) in active patients 1

MRI Findings Managed Conservatively

• Degenerative meniscal changes in patients ≥40 years: Continue exercise therapy; surgery not indicated 5
• Mild chondromalacia or early osteoarthritis: Exercise, weight loss, NSAIDs, and self-management 5
• Bone marrow edema without fracture: Activity modification and monitoring 6

Critical Pitfall in Older Patients

• In patients >70 years, the majority have asymptomatic meniscal tears; MRI findings may be misleading and should not drive surgical decisions without correlating symptoms 6, 5