What is the diagnosis and treatment for bilateral knee pain and swelling with a feeling of vibration on the anterior aspect and stiffness at night, without any articular or rheumatological issues?

Diagnosis: Prepatellar Bursitis or Patellofemoral Pain Syndrome

Based on the clinical presentation of bilateral anterior knee pain and swelling with a vibration sensation and night stiffness, without articular or rheumatological findings, the most likely diagnosis is prepatellar bursitis or patellofemoral pain syndrome (PFPS), and initial management should focus on conservative therapy with exercise, patient education, and acetaminophen up to 4g/day. 1

Clinical Reasoning

The "feeling of vibration" in the anterior knee is an unusual descriptor that may represent:

• Crepitus from patellofemoral tracking abnormalities 2
• Fluid movement within a bursa or joint effusion 3
• Synovial inflammation causing abnormal sensations 4

The bilateral nature with anterior location strongly suggests patellofemoral pathology rather than meniscal or ligamentous injury, which typically presents unilaterally 5, 6. Night stiffness without morning stiffness lasting >30 minutes makes inflammatory arthritis less likely, even though rheumatological factors are already negative 2.

Diagnostic Workup

Initial Imaging

• Start with plain radiographs including AP, lateral, Merchant/sunrise, and tunnel views of both knees 1
• Radiographs evaluate for osteoarthritis, patellar malalignment, and other bony abnormalities 7, 1
• Approximately 20% of patients inappropriately undergo MRI without recent radiographs, which should be avoided 8

Advanced Imaging (If Radiographs Normal)

• MRI without contrast is indicated when radiographs are normal or non-diagnostic to evaluate 1, 8:

  • Meniscal pathology
  • Cartilage lesions
  • Bone marrow edema
  • Synovitis and effusions
  • Prepatellar or infrapatellar bursitis

• Ultrasound can detect synovial pathology, effusions, and cortical changes, and can demonstrate increased synovial blood flow associated with knee pain 7

• Power Doppler ultrasound shows reduced blood flow correlating with pain reduction after joint injections 7

Joint Aspiration

• If effusion is present, US- or fluoroscopy-guided aspiration should be performed for synovial fluid analysis to exclude crystal disease or infection 7
• This is particularly important given the bilateral presentation and night symptoms 3

Treatment Algorithm

First-Line Conservative Management

The American Academy of Orthopaedic Surgeons recommends initial conservative therapy consisting of: 1

• Exercise therapy focusing on hip and knee strengthening 2
• Patient education and self-management programs 2
• Acetaminophen up to 4g/day in adults as first-line oral analgesic 1

Additional Conservative Options

• Weight loss if patient is overweight 2
• Physiotherapy for biomechanical correction 7
• Simple analgesia is preferable to NSAIDs 7

NSAIDs Considerations

• Short-term NSAID use may be considered if symptoms are severe, but carries risk 7
• NSAIDs are more effective than simple analgesia for pain relief but should be used cautiously 7
• No high-quality evidence shows COX-2 inhibitors are safer than non-selective agents 7

Interventional Options (If Conservative Fails)

• Local corticosteroid injection if symptoms don't resolve rapidly with conservative management 7
• US-guided aspiration may provide temporary relief for symptomatic effusions 9
• Corticosteroid injection into the knee joint may be beneficial when associated synovitis is present 9

Critical Pitfalls to Avoid

Don't Miss Referred Pain

• Hip pathology must be excluded when knee radiographs are unremarkable 8
• Obtain hip radiographs if clinical suspicion exists (groin pain, limited hip range of motion, positive impingement signs) 8
• Lumbar spine pathology can refer pain to the knee; obtain lumbar radiographs if radiculopathy or neurogenic claudication patterns are present 8

Don't Overlook Baker's Cyst

• A popliteal (Baker's) cyst can present with posterior knee fullness and may extend anteriorly 9
• Ruptured Baker's cyst mimics DVT with sudden calf pain and swelling 9
• Ultrasound is the preferred initial diagnostic tool to confirm or exclude this 9

Age-Specific Considerations

• In patients >70 years, bilateral structural abnormalities on imaging may not correlate with symptoms 7
• Patellofemoral pain typically affects people <40 years who are physically active, with 25% lifetime prevalence 2
• The presence of anterior knee pain during squatting is 91% sensitive and 50% specific for patellofemoral pain 2

When to Consider Rheumatology Referral

• If symptoms persist despite addressing metabolic deficiencies and controlling inflammation 7
• For persistent arthropathy not related to any identifiable cause 7
• Early referral prevents long-term disability in axial spondyloarthropathy, though this typically presents with lower back pain 7

Prognosis and Follow-up

• Most anterior knee pain responds to comprehensive conservative treatment over 4-6 weeks 2
• Surgical intervention is rarely indicated and reserved for patients with identifiable structural abnormalities who fail nonoperative management 5
• The source of patellofemoral pain cannot always be sufficiently explained, and multiple tissue structures may contribute simultaneously 6, 4