What is the appropriate initial evaluation and management for a patient presenting with tenderness to palpation over the lateral left knee?

Approach to Lateral Left Knee Tenderness

Obtain plain radiographs (AP, lateral at 25-30° flexion, and patellofemoral views) as the initial imaging study, even if Ottawa Knee Rule criteria are not met, because lateral knee tenderness warrants evaluation for fracture, osteochondritis dissecans, and other bony pathology before considering soft tissue diagnoses. 1, 2, 3

Initial Clinical Assessment

Determine if any Ottawa Knee Rule criteria are present, which mandate radiographs: 1, 2, 3

• Age >55 years
• Isolated patellar tenderness (not applicable here)
• Tenderness at the head of the fibula
• Inability to flex knee to 90°
• Inability to bear weight for 4 steps immediately after injury or in the examination room

Key point: Even without meeting Ottawa criteria, lateral knee tenderness should prompt radiographic evaluation because clinical examination alone has limited reliability for excluding significant pathology. 1, 2

Specific Physical Examination Findings to Document

Focus your examination on these critical elements: 1, 4

• Exact location of tenderness: Distinguish between fibular head, lateral femoral epicondyle, lateral joint line, or iliotibial band insertion
• Presence of joint effusion: Indicates potential intra-articular pathology including osteochondritis dissecans 1
• Range of motion limitations: Loss of motion or crepitus suggests intra-articular disease 1
• Mechanical symptoms: Locking, catching, popping, or giving way indicate possible loose bodies or meniscal pathology 1
• Stability testing: Assess lateral collateral ligament and posterolateral corner 4

Initial Imaging Protocol

Standard radiographic series should include: 2, 3

• Anteroposterior (AP) view
• Lateral view with knee at 25-30° flexion
• Patellofemoral (sunrise/Merchant) view
• Tunnel view to evaluate for osteochondritis dissecans if patient is adolescent or young adult 1

The lateral view at 25-30° flexion is critical because it can demonstrate lipohemarthrosis (indicating occult intra-articular fracture) when obtained as a cross-table lateral with horizontal beam. 2, 3

Differential Diagnosis Based on Location

Lateral femoral epicondyle tenderness: 5, 6

• Iliotibial band syndrome (most common in runners/cyclists)
• Iliotibial band enthesopathy
• Lateral collateral ligament injury

Fibular head tenderness: 1, 2

• Fibular head fracture (requires radiographs per Ottawa rules)
• Proximal tibiofibular joint injury
• Lateral collateral ligament avulsion

Lateral joint line tenderness: 1, 4

• Lateral meniscus tear
• Osteochondritis dissecans
• Lateral compartment osteoarthritis

Posterior-lateral tenderness: 7

• Popliteal tendon pathology (rare cause of snapping/popping)
• Baker cyst
• Posterolateral corner injury

When to Proceed to MRI

Order MRI without contrast if: 1, 2, 4

• Radiographs are negative but significant joint effusion is present
• Mechanical symptoms (locking, catching, giving way) persist
• Inability to fully bear weight after 5-7 days despite negative radiographs
• Clinical suspicion for meniscal tear, ligamentous injury, or osteochondritis dissecans remains high
• Patient is adolescent/young adult with suspected osteochondritis dissecans on radiographs (MRI characterizes lesion stability) 1

MRI is particularly valuable for characterizing osteochondritis dissecans lesions or when concomitant pathology such as meniscal tears or ligament injuries is suspected. 1

Critical Pitfalls to Avoid

Never skip radiographs before ordering MRI — approximately 20% of patients inappropriately receive MRI without recent radiographs, which is suboptimal care. 2, 3

Do not dismiss lateral knee pain as simple iliotibial band syndrome without imaging — case reports document missed diagnoses including snapping popliteal tendon and osteochondritis dissecans that were initially misdiagnosed as IT band syndrome. 5, 7

Clinical judgment supersedes decision rules — obtain radiographs even without Ottawa criteria if there is gross deformity, palpable mass, penetrating injury, prosthetic hardware, altered mental status, neuropathy, or history suggesting increased fracture risk. 2, 3

Initial Management Pending Imaging

While awaiting radiographs: 5, 4

• Activity modification (avoid aggravating activities)
• Ice application
• NSAIDs if not contraindicated
• Consider knee immobilizer if unable to bear weight comfortably

Do not inject corticosteroids until fracture and other serious pathology are excluded by imaging. 8