What is the recommended approach for examining and managing knee pain in an adult patient with no significant medical history?

Knee Pain Examination and Management

Initial Imaging Approach

Start with plain radiographs of the knee including anteroposterior (or Rosenberg/tunnel view), tangential patellar view, and lateral view—this is the mandatory first imaging study for any adult with chronic knee pain. 1

• Radiographs remain the initial imaging modality regardless of suspected pathology, as they identify osteoarthritis (the most common cause), chondrocalcinosis, osteochondritis dissecans, loose bodies, and signs of prior injury 1
• Approximately 20% of patients inappropriately receive MRI without recent radiographs within the prior year—this represents premature and unnecessary imaging 1

Physical Examination Components

Key Clinical Features to Assess

For osteoarthritis (most common cause):

• Limited range of motion, crepitus in the patellofemoral compartment, and joint line tenderness 2
• Varus or valgus alignment deformities in more severe cases 2
• Pain with weight-bearing activities involving knee flexion (squatting, stairs, running) 3

For ligament injuries:

• Specific ligament stress tests remain as accurate or more accurate than advanced imaging for diagnosis 4
• A thorough understanding of knee anatomy and proper examination technique is essential 4

For meniscal pathology:

• McMurray test for meniscal tears, though this may cause increased pain in patients with concurrent osteoarthritis 2
• Clinical examination is 62% sensitive for medial meniscal tears but only 14% sensitive for lateral meniscal tears 5

For patellofemoral disease:

• Clinical examination is 100% sensitive for detecting patellofemoral pathology 5

Critical Referred Pain Assessment

Always examine the hip and lumbar spine—referred pain from these regions commonly masquerades as knee pain, especially when knee radiographs are unremarkable. 1, 6

• Hip pathology frequently refers pain to the knee and requires dedicated hip radiographs if knee imaging is unrevealing 1, 6
• Lumbar spine pathology must be considered with appropriate clinical examination before attributing all symptoms to knee pathology 1, 6

Advanced Imaging Algorithm

When Initial Radiographs Are Normal or Show Only Effusion

Proceed to MRI without IV contrast—this is the next indicated examination when pain persists despite normal or minimally abnormal radiographs. 1

MRI detects:

• Bone marrow lesions (BMLs) and synovitis/effusion, which indicate the origin of knee pain in osteoarthritis 1
• Subchondral insufficiency fractures (previously termed spontaneous osteonecrosis), most common in middle-aged to elderly females involving the medial femoral condyle 1
• Meniscal tears, though these are often incidental findings—the majority of people over 70 have asymptomatic meniscal tears, and likelihood of tears in painful versus asymptomatic knees is not significantly different in patients 45-55 years 1
• Popliteal cysts, including rupture and communication with the joint 1, 6
• Articular cartilage abnormalities and subchondral cysts 1

Important caveat: New or increasing BMLs correlate with increased knee pain, especially in males or patients with family history of osteoarthritis, while decreasing BMLs correlate with reduced pain 1

When Radiographs Show Chondrocalcinosis

Joint aspiration with synovial fluid analysis is indicated when effusion is present to confirm crystal disease (pseudogout/CPPD) or exclude infection. 7

• Aspiration can be performed under ultrasound or fluoroscopic guidance 1, 7
• Radiographs effectively demonstrate characteristic calcifications of fibrocartilage (menisci) and hyaline cartilage 7
• Ultrasound can detect chondrocalcinosis and may outperform radiography, demonstrating the "double contour sign" 7

When Radiographs Show Osteochondritis Dissecans, Loose Bodies, or Prior Cartilage/Meniscal Repair

MRI without IV contrast is indicated to determine fragment stability, grade repair sites, and guide treatment options. 1

• CT without IV contrast may be used to confirm loose bodies when MRI is not definitive 1
• CT arthrography can evaluate menisci, articular cartilage, and loose bodies as an alternative to MRI 1

Role of Contrast-Enhanced MRI

MRI without and with IV contrast is not usually indicated for initial evaluation but may be appropriate for specific conditions: 1

• Hoffa's disease, deep infrapatellar bursitis, patellofemoral friction syndrome, and adhesive capsulitis 1
• Quantifying synovitis degree (enhancing synovitis >2mm in Hoffa's fat correlates with peripatellar pain) 1
• Pigmented villonodular synovitis 1

Ultrasound Utility

Ultrasound has limited but specific roles—it should not be used as a comprehensive screening tool. 1, 6

• Confirming suspected effusion and guiding aspiration 1
• Detecting popliteal cysts and cyst rupture (as accurate as MRI) 1, 6
• Evaluating medial plicae and iliotibial band syndrome 1
• Detecting loose bodies in specific locations 6

Common Pitfalls to Avoid

Do not assume normal radiographs exclude significant pathology—this is the most critical error in knee pain evaluation. 8, 6

• Subchondral insufficiency fractures, early osteochondritis dissecans, stress fractures, and bone marrow edema are invisible on plain films 1, 8
• Radiographs may be initially normal in subchondral insufficiency fractures, later revealing articular surface fragmentation and progressive osteoarthritis 1

Do not order MRI with IV contrast as the initial advanced imaging study—contrast is unnecessary for evaluating most causes of chronic knee pain including bone marrow edema, cartilage injury, and meniscal pathology. 8

Do not overlook referred pain sources before attributing all symptoms to knee pathology—complete hip and lumbar spine examination should precede knee-focused imaging. 6

Do not assume all meniscal tears seen on MRI are symptomatic—meniscal tears are frequently incidental, particularly in patients over 45 years. 1, 6

Do not use CT as the initial advanced imaging study—it provides inferior soft tissue and cartilage detail compared to MRI. 8

Do not use bone scan for initial evaluation—it lacks specificity and anatomic resolution compared to MRI. 8

Treatment Considerations

When conservative treatment fails, consider interventional options in this sequence: 9

• Intra-articular corticosteroid injections (proven effective) 9
• Radiofrequency ablation (conventional and cooled) of genicular nerves (proven effective) 9
• Hyaluronic acid infiltrations (conditionally recommended) 9
• Platelet-rich plasma, chemical ablation of genicular nerves, and neurostimulation (insufficient evidence, consider only in study settings) 9

Joint-preserving and joint-replacement decisions should be made through multidisciplinary discussion including orthopedic surgery. 9