What investigation should be done for a patient with typical knee osteoarthritis presenting with joint clicking?

No Additional Investigation Required for Typical Knee OA with Joint Clicking

In a patient with typical knee osteoarthritis presenting with joint clicking (crepitus), no additional investigation is needed beyond the initial clinical diagnosis—the clicking is a characteristic finding of established OA and does not warrant further workup unless atypical features are present.

Clinical Context of Crepitus in Knee OA

Joint clicking or crepitus is an expected physical examination finding in knee osteoarthritis and actually supports the diagnosis rather than suggesting additional pathology:

• Crepitus occurs in approximately 81% of patients with established osteoarthritis, making it a common and characteristic feature of the disease 1
• The presence of coarse crepitus is one of the diagnostic criteria used by the American College of Rheumatology for clinical diagnosis of knee OA 1
• Crepitus increases the odds of radiographic osteoarthritis by more than threefold (OR 3.79,95% CI 1.99 to 7.24), confirming it as a marker of the disease rather than a red flag 1

When Investigation IS Required

Imaging or further workup becomes necessary only when atypical features are present that suggest alternative or additional diagnoses 2, 1:

Red Flags Requiring Investigation:

• Age <40 years with joint symptoms 2
• Prolonged morning stiffness (>30 minutes, suggesting inflammatory arthritis rather than OA's typical brief stiffness) 2
• Rapid symptom progression or sudden change in clinical characteristics 2, 1
• Marked inflammatory signs: significant warmth, large effusion, or systemic symptoms 2
• Mechanical symptoms suggesting concomitant pathology: true locking (not just clicking), catching, or giving way that suggests meniscal tears or loose bodies 3, 1
• Unexpected rapid progression in established OA 2, 1

Diagnostic Algorithm for Knee OA with Clicking

Patient >40 years with typical OA presentation + clicking:

• No imaging needed if diagnosis already established clinically 2, 1
• Clicking/crepitus is an expected finding that confirms rather than contradicts the diagnosis 1, 4
• Management should focus on symptoms and function, not the presence of crepitus 3

If atypical features present:

• Order standing radiographs first (AP, lateral, tunnel, and tangential patellar views) to confirm diagnosis and exclude alternatives 1
• Consider MRI without contrast only if radiographs are normal/non-diagnostic and symptoms persist, or if true mechanical symptoms suggest meniscal pathology 1, 5

Critical Pitfalls to Avoid

• Do not order routine imaging for established OA with crepitus alone—this is a normal finding in OA and does not indicate disease progression or need for intervention 2, 1
• Do not confuse clicking/crepitus with true mechanical locking—the former is benign articular noise from cartilage irregularity, while the latter suggests meniscal tears or loose bodies requiring further evaluation 3, 1
• Remember that the majority of people over 70 have asymptomatic meniscal tears, so even if imaging shows a tear, it may not be the source of symptoms 1
• Clinical symptoms and functional impact should drive management, not radiographic findings or the presence of crepitus 2