How should I evaluate and initially manage an adolescent presenting with a sore knee?

Evaluation and Initial Management of Adolescent Knee Pain

Start with plain radiographs (AP and lateral views) if the adolescent meets any Ottawa Knee Rule criteria, then proceed to targeted physical examination to identify the specific cause, with most adolescent knee pain responding to conservative management focused on exercise therapy and activity modification. 1

Initial Imaging Decision

Order knee radiographs immediately if any of the following Ottawa Knee Rule criteria are present: 1

• Age ≥55 years (less relevant for adolescents, but include for completeness)
• Isolated tenderness at the patella
• Tenderness at the fibular head
• Inability to flex knee to 90 degrees
• Inability to bear weight for 4 steps immediately after injury or in the examination room

Obtain radiographs regardless of Ottawa criteria if: 1

• Gross deformity present
• Palpable mass
• Penetrating injury
• Altered mental status
• History suggesting increased fracture risk (e.g., bone disease, high-energy trauma)

Minimum two views required: anteroposterior and lateral (with knee at 25-30 degrees flexion). 1

Age-Specific Differential Diagnosis Patterns

Adolescent girls and young women most commonly present with: 2

• Patellofemoral pain syndrome (lifetime prevalence ~25%, typically <40 years old) 3
• Patellar subluxation or tracking problems 2

Adolescent boys and young men most commonly present with: 2

• Osgood-Schlatter disease (tibial apophysitis) 2, 4
• Patellar tendonitis (jumper's knee) 2, 4

Active adolescent athletes across genders may present with: 2

• Acute ligamentous sprains
• Overuse injuries (pes anserine bursitis, medial plica syndrome)
• Meniscal tears from twisting injuries (in <40 years, typically traumatic rather than degenerative) 3

Critical Physical Examination Maneuvers

For patellofemoral pain (most common in adolescents): 3

• Anterior knee pain during squat test (91% sensitive, 50% specific)
• Pain with patellar compression or tracking
• Assess for J-sign (lateral patellar tracking during extension)

For meniscal tears: 3

• McMurray test: concurrent knee rotation (internal for lateral meniscus, external for medial meniscus) with extension (61% sensitive, 84% specific)
• Joint line tenderness (83% sensitive, 83% specific)

For ligamentous injury: 1

• Assess joint stability including collateral and cruciate ligaments
• Evaluate for joint effusion (>10mm on lateral radiograph warrants further investigation) 5

Red flags requiring urgent evaluation: 6

• Fever with joint pain (septic arthritis until proven otherwise)
• Inability to bear weight or move the joint
• Significant joint effusion with systemic symptoms
• Recent infection or bacteremia elsewhere

When to Advance to MRI

Order MRI without contrast if radiographs are negative but: 1, 5

• Inability to fully bear weight after 5-7 days
• Significant joint effusion present
• Mechanical symptoms suggesting meniscal injury (locking, catching, giving way)
• Joint instability suggesting ligamentous injury
• High clinical suspicion for internal derangement despite negative X-rays

Initial Conservative Management

First-line treatment for most adolescent knee pain (patellofemoral pain, Osgood-Schlatter, patellar tendinitis): 3, 4

• Hip and knee strengthening exercises (particularly quadriceps and hip abductors)
• Activity modification and relative rest (not complete immobilization)
• Ice application after activity
• Education and self-management programs

For patellofemoral pain specifically: 3

• Combination of hip/knee strengthening with foot orthoses or patellar taping
• No indication for surgery

For suspected meniscal tears: 3

• Exercise therapy for 4-6 weeks as first-line treatment
• Surgery only indicated for severe traumatic tears with displaced tissue (bucket-handle tears)
• Degenerative tears: exercise therapy even with mechanical symptoms (surgery not indicated)

Common Pitfalls to Avoid

Do not assume negative radiographs exclude significant pathology - soft tissue injuries (meniscal tears, ligamentous injuries) require MRI for diagnosis. 1, 5

Do not order MRI as initial imaging - approximately 20% of patients inappropriately receive MRI without recent radiographs, which should always be obtained first. 1

Do not overlook referred pain - hip pathology (including slipped capital femoral epiphysis in adolescents) commonly refers pain to the knee and should be considered if knee examination is unremarkable. 1, 2

Do not rush to surgery for degenerative or non-displaced meniscal tears - conservative management with exercise therapy is first-line treatment and surgery does not improve outcomes. 3

Do not miss septic arthritis - any adolescent with acute severe knee pain, fever, inability to bear weight, and elevated inflammatory markers (CRP >2.0 mg/dL) requires urgent joint aspiration and orthopedic consultation. 6

Follow-Up Timeline

Reassess in 5-7 days if: 1

• Conservative management initiated
• Ability to bear weight not improving
• Mechanical symptoms developing

Consider specialist referral if: 1, 5

• Persistent symptoms beyond 4-6 weeks of appropriate conservative therapy
• Joint instability with activities
• MRI reveals significant structural pathology requiring surgical evaluation