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 cartilage disruption 5

Critical Referred Pain Assessment

Always examine the hip and lumbar spine before attributing all symptoms to knee pathology—this is a common diagnostic pitfall. 1, 6

• Hip pathology frequently refers pain to the knee; obtain dedicated hip radiographs if knee imaging is unremarkable 1, 6
• Lumbar spine pathology can cause referred knee pain, especially when knee radiographs are normal 1, 6

Advanced Imaging Algorithm

When Radiographs Are Normal or Show Only Effusion

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

MRI detects:

• Bone marrow lesions (BMLs) and synovitis—both strongly associated with knee pain in osteoarthritis 1
• Subchondral insufficiency fractures (previously termed spontaneous osteonecrosis), which are often initially normal on radiographs 1
• Meniscal tears, though these are frequently incidental findings: the majority of patients over 70 years have asymptomatic tears, and likelihood of tears in painful versus asymptomatic knees is not significantly different in patients 45-55 years old 1
• Articular cartilage abnormalities, effusion extent, synovitis, and popliteal cyst presence or rupture 1

Important caveats:

• New or increasing BMLs correlate with increased knee pain, especially in males or those with family history of osteoarthritis 1
• Patellofemoral cartilage loss with active knee pain correlates with BMLs 1
• MRI with IV contrast is not routinely indicated but may be more accurate for Hoffa's disease, deep infrapatellar bursitis, patellofemoral friction syndrome, and quantifying synovitis 1

When Radiographs Show Chondrocalcinosis

If chondrocalcinosis is present, perform joint aspiration with synovial fluid analysis to confirm calcium pyrophosphate deposition disease (pseudogout) or exclude infection. 7

• Aspiration can be guided by ultrasound or fluoroscopy 1, 7
• Ultrasound outperforms radiography for detecting chondrocalcinosis and can demonstrate the "double contour sign" 7
• MRI without contrast may be indicated if symptoms persist despite radiographic findings, to evaluate for synovitis or bone marrow lesions not explained by chondrocalcinosis alone 7

When Radiographs Show Osteochondritis Dissecans or Loose Bodies

MRI without IV contrast is indicated to determine fragment stability and guide treatment, as hyperintense rim or cysts at fragment periphery indicate instability. 1

• CT without contrast may be used to confirm loose bodies when MRI is not definitive, as it has superior spatial resolution for cortical bone 1
• CT arthrography can evaluate menisci, articular cartilage, and loose bodies when MRI is contraindicated 1

When Radiographs Show Osteoarthritis

MRI is not routinely indicated for radiographically confirmed osteoarthritis unless symptoms are unexplained by imaging findings (such as stress fractures) or serial cartilage measurements are needed. 1

• MRI has increased sensitivity for osteoarthritis and may be appropriate when more accurate cartilage assessment is desired 1

Alternative Imaging Modalities

Ultrasound has limited utility:

• Appropriate for confirming suspected effusion and guiding aspiration 1
• Accurate for diagnosing popliteal cysts and detecting cyst rupture (comparable to MRI) 1, 6
• Useful for evaluating medial plicae and iliotibial band syndrome 1
• Not useful as a comprehensive screening test 1

CT without contrast:

• Indicated for evaluating patellofemoral anatomy in chronic pain related to repetitive subluxation or maltracking 1
• Can assess trochlear morphology and tibial tubercle-trochlear groove distance 1

Bone scan:

• Not indicated when initial radiographs are negative or show only effusion 1

Common Diagnostic Pitfalls

• Do not skip radiographs and proceed directly to MRI—this violates established imaging algorithms and wastes resources 1
• Do not attribute all knee pain to meniscal tears seen on MRI in older patients—these are frequently asymptomatic incidental findings 1
• Do not overlook referred pain from hip or lumbar spine—always perform thorough clinical examination of these regions 1, 6
• Do not assume normal radiographs exclude significant pathology—subchondral insufficiency fractures, early osteochondritis dissecans, and bone marrow lesions require MRI for detection 1

Treatment Decision Framework

The majority of reversible causes of knee pain are diagnosed by physical examination alone. 5

• If physical examination suggests internal derangement requiring surgical intervention, proceed directly to standard arthroscopy for both diagnosis and treatment 5
• MRI or needle arthroscopy should be reserved for cases where diagnosis remains unclear after history and physical examination 5
• When conservative treatment fails, consider intra-articular corticosteroid injections and radiofrequency ablation of genicular nerves, both of which have demonstrated effectiveness 8
• Hyaluronic acid infiltrations are conditionally recommended 8
• Joint replacement decisions should be made through multidisciplinary discussion 8