How should I evaluate and manage a patient with localized articular surface pain suggestive of cartilage degeneration?

Evaluation and Management of Articular Cartilage Pain

Initial Diagnostic Approach

Begin with plain radiographs (anteroposterior and lateral views minimum) as the first-line imaging study for any patient presenting with localized articular surface pain. 1, 2 This establishes baseline joint architecture, detects joint space narrowing, identifies osteochondral defects, and rules out fractures or loose bodies that may not be clinically apparent. 1

Key Clinical Features to Document

• Pain characteristics: Localized to the joint versus periarticular structures (tendons, bursae, ligaments). 3 Pain with specific activities without prolonged morning stiffness suggests periarticular pathology rather than true articular cartilage disease. 3
• Mechanical symptoms: Catching, locking, or giving way suggests intra-articular pathology such as loose bodies, meniscal tears, or unstable osteochondral fragments. 1
• Effusion presence: Joint swelling indicates active intra-articular pathology and justifies both imaging and potential aspiration. 1, 2

Physical Examination Priorities

• Range of motion testing: Restricted motion in all planes suggests true articular pathology versus selective limitation with periarticular disease. 3
• Provocative maneuvers: Specific movements that reproduce pain help localize the lesion (e.g., patellofemoral compression for anterior knee pain). 1
• Palpation: Point tenderness over periarticular structures versus diffuse joint line tenderness. 3

Advanced Imaging Algorithm

When Radiographs Are Normal or Show Only Effusion

Proceed directly to MRI without IV contrast as the next imaging study. 1, 2 MRI provides superior visualization of:

• Articular cartilage integrity: Detects chondral defects, delamination, and early degenerative changes not visible on radiographs. 1
• Subchondral bone marrow lesions (BMLs): New or increasing BMLs correlate strongly with knee pain, particularly in males and patients with family history of osteoarthritis. 1 Conversely, decreasing BMLs associate with reduced pain. 1
• Synovitis and effusion: Both indicate potential pain sources in osteoarthritis, with enhancing synovitis >2mm thickness correlating with peripatellar pain. 1
• Subchondral insufficiency fractures: MRI detects these earlier than radiographs, which are often initially normal. 1

Special Imaging Considerations

• 3T MRI with quantitative imaging (T2 mapping): Consider in patients aged 45-55 years with normal radiographs but persistent pain, as elevated T2 values indicate early cartilage degeneration. 1
• CT without contrast: Reserve for evaluating cartilage abnormalities extending to the articular surface when MRI is non-diagnostic, as CT provides superior spatial resolution at the cartilage-bone interface. 1
• MR arthrography: Not indicated as a second examination; reserve for patients with prior meniscal surgery, known chondral/osteochondral lesions, or suspected loose bodies. 1

Ultrasound Role

Ultrasound is not useful as a screening test for articular cartilage pathology. 1 Its acoustic window is too limited to evaluate acetabular or femoral head cartilage in the hip, and it cannot comprehensively assess knee cartilage. 1 However, ultrasound is appropriate for:

• Confirming suspected effusion and guiding aspiration. 1
• Evaluating periarticular structures (tendons, bursae) when periarticular pathology is suspected. 3

Diagnostic Injection Strategy

When multiple sites of degenerative joint disease are present or the pain source is unclear, perform image-guided (fluoroscopy, CT, or ultrasound) intra-articular anesthetic injection with or without corticosteroid. 1 This serves dual purposes:

• Diagnostic confirmation: >70-80% pain relief confirms intra-articular origin and guides surgical planning. 1, 3
• Therapeutic trial: Corticosteroid injections reduce synovitis on MRI in two-thirds of patients for 1-2 weeks, though 70% develop recurrent pain with subsequent synovial volume increase. 1

Laboratory Evaluation

If inflammatory arthritis is suspected (prolonged morning stiffness, systemic symptoms, multiple joint involvement), obtain inflammatory markers (ESR, CRP) and autoimmune panel (RF, anti-CCP, ANA). 4 Joint aspiration with synovial fluid analysis is mandatory if infection or crystal disease is considered. 1, 4

Management Algorithm Based on Imaging Findings

For Focal Chondral Defects (<4 cm²) with Minimal Osteoarthritis

Consider arthroscopic microfracture as first-line surgical intervention in younger patients (age ≤50 years). 1 The procedure involves:

1. Debridement of friable cartilage to create a well-contained lesion with perpendicular edges of healthy cartilage. 1
2. Creating 3-4mm deep perpendicular holes in subchondral bone, spaced 3-4mm apart, using a microfracture awl. 1
3. Goal is to recruit pluripotent marrow cells and growth factors to form fibrocartilage repair tissue. 1

For Osteochondral Lesions

MRI is essential to determine fragment stability. 1 A hyperintense rim or cysts at the osteochondral fragment periphery on MRI indicates instability (sensitivity 97%), appearing as high signal on T2-weighted images. 1 Unstable fragments require surgical fixation or removal. 1

For Diffuse Osteoarthritis

MRI is not routinely indicated when radiographs are diagnostic of osteoarthritis unless symptoms are unexplained by radiographic findings (e.g., to rule out stress fractures or subchondral insufficiency fractures). 1 However, MRI may be indicated when:

• Serial cartilage measurements are needed for research or monitoring. 1
• Unilateral symptoms exist with bilateral radiographic changes (MRI helps discriminate painful from non-painful knees). 1
• Synovitis or effusion on MRI combined with Kellgren-Lawrence score ≥2 are the best discriminators between painful and asymptomatic knees. 1

Critical Pitfalls to Avoid

• Do not order MRI without recent radiographs first: Approximately 20% of patients with chronic knee pain inappropriately receive MRI without prior radiographs. 2 This wastes resources and may miss fractures or loose bodies better seen on plain films. 1

• Do not assume all meniscal tears are symptomatic: The majority of people over 70 years have asymptomatic meniscal tears, and tear likelihood is similar in painful versus asymptomatic knees in patients aged 45-55 years. 1 Correlation with clinical findings is essential. 1

• Do not overlook referred pain: Hip pathology commonly refers pain to the knee, and lumbar spine pathology can mimic knee pain. 2 Consider imaging the hip or spine if knee imaging is unremarkable. 1, 2

• Do not assume periarticular pain is articular: Many conditions (bursitis, tendinopathy, fat pad impingement) mimic intra-articular pathology. 1, 3 Diagnostic injection can differentiate. 3

• Do not ignore bone marrow lesions: BMLs are strong pain correlates and may indicate subchondral insufficiency fractures requiring protected weight-bearing. 1 Radiographs may be initially normal, with later progression to articular surface fragmentation and collapse. 1