What could be causing bilateral knee pain below the patella with no history of injury?

Bilateral Knee Pain Below the Patella Without Trauma

Start with plain radiographs of both knees, and if normal, this is most likely patellofemoral pain syndrome (PFPS), which should be managed with physical therapy focusing on hip and knee strengthening exercises—surgery is not indicated. 1, 2

Initial Diagnostic Approach

First-Line Imaging

• Obtain bilateral knee radiographs (frontal, lateral, and tangential patellar views) as the initial imaging study for chronic knee pain lasting 2 months 1, 3
• Radiographs help exclude osteoarthritis, osteochondral defects, Osgood-Schlatter disease, Sinding-Larsen-Johansson syndrome, and degenerative changes 1, 4

When to Consider MRI

• MRI without IV contrast is indicated only if: radiographs are normal but symptoms persist despite 4-6 weeks of conservative treatment, or if surgery is being considered 1, 3
• MRI is useful for evaluating Osgood-Schlatter or Sinding-Larsen-Johansson syndrome if suspected based on age and clinical presentation 1

Most Likely Diagnosis: Patellofemoral Pain Syndrome

Clinical Features Supporting PFPS

• Pain location: Peripatellar or retropatellar pain (right below the patella on both sides fits this pattern) 5, 6
• Age consideration: PFPS typically affects people younger than 40 years who are physically active, with a lifetime prevalence of approximately 25% 2
• Diagnostic test: Anterior knee pain during a squat is 91% sensitive and 50% specific for patellofemoral pain 2
• Bilateral presentation: Common in PFPS due to underlying biomechanical factors affecting both knees 5, 7

Physical Examination Findings to Assess

• Patellar mobility and tracking during knee flexion/extension 6
• Quadriceps strength, particularly vastus medialis versus vastus lateralis imbalance 7
• Hip muscle strength and postural control 5, 7
• Joint effusion, range of motion, and resisted isometrics 5

Treatment Algorithm for PFPS

First-Line Conservative Management (Minimum 3 Months)

• Hip and knee strengthening exercises are central to successful management 5, 2
• Specific focus on correcting vastus medialis-vastus lateralis imbalance before progressing to general quadriceps strengthening 7
• Foot orthoses or patellar taping in combination with strengthening exercises 2
• Stretching exercises and aerobic conditioning 5

Complementary Treatments

• Patellofemoral joint mobilizations 5
• Neuromuscular training and gait retraining 5
• Patient education about activity modification and self-management 2, 6

Treatment Phases

1. Phase 1: Reduce pain/swelling, restore vastus medialis-lateralis balance, normalize gait, decrease patellofemoral joint loading 7
2. Phase 2: Improve postural control, increase quadriceps and hip strength, restore knee function 7
3. Phase 3: Functional exercises and return to regular physical activity 7

Critical Differential Diagnoses to Exclude

Referred Pain Sources

• Lumbar spine pathology: Must be considered if knee radiographs are unremarkable, especially with bilateral presentation 8, 9
• Hip pathology: Can refer pain to the knee region 8
• Perform thorough clinical examination of lumbar spine and hips before attributing all symptoms to knee pathology 8

Age-Specific Considerations

• If patient is ≥45 years old: Consider knee osteoarthritis, which presents with activity-related joint pain and less than 30 minutes of morning stiffness (95% sensitivity, 69% specificity) 2
• If adolescent/young adult: Consider Osgood-Schlatter disease (tibial tuberosity apophysitis) or Sinding-Larsen-Johansson syndrome (inferior pole patella) 1

Common Pitfalls to Avoid

• Do not order MRI prematurely: Approximately 20% of patients with chronic knee pain have MRI performed without recent radiographs 8
• Do not rush to surgery: There is no indication for surgery in PFPS; surgery should only be considered after failure of comprehensive rehabilitation program lasting at least 3 months 2, 6, 7
• Do not overlook referred pain: Complete assessment of lumbar spine and hip before rushing to knee-specific imaging 8
• Limited role for NSAIDs: Little evidence supports routine use of nonsteroidal anti-inflammatory drugs or knee braces for PFPS 6

When Conservative Treatment Fails

• If symptoms persist after 3 months of appropriate physical therapy, reconsider the diagnosis 7
• Obtain MRI without IV contrast to evaluate for alternative pathology (meniscal tears, cartilage injury, loose bodies) 1, 3
• Re-evaluate for referred pain from lumbar spine or hip 8, 9