Differential Diagnosis for Burning Pain in Knee when Extended

• Single most likely diagnosis
  • Patellofemoral Pain Syndrome (PFPS): This condition is characterized by pain around or behind the patella, often exacerbated by activities that load the patellofemoral joint, such as knee extension. The burning pain when the knee is extended is a classic symptom of PFPS.
• Other Likely diagnoses
  • Osgood-Schlatter Disease: This condition affects the tibial tubercle, where the patellar tendon attaches, and can cause knee pain, especially with extension. It's more common in adolescents.
  • Quadriceps Tendinopathy: Inflammation or degeneration of the quadriceps tendon can cause pain in the front of the knee, which may worsen with knee extension.
  • Prepatellar Bursitis: Inflammation of the bursa in front of the patella can cause pain and swelling, especially with knee extension or direct pressure.
• Do Not Miss diagnoses
  • Septic Arthritis: Although less common, septic arthritis is a medical emergency that requires prompt diagnosis and treatment. It can cause severe pain, swelling, and warmth of the joint, and can be associated with systemic symptoms like fever.
  • Osteonecrosis of the Knee: This condition involves the death of bone tissue due to lack of blood supply and can cause severe pain, especially with weight-bearing activities or knee extension.
• Rare diagnoses
  • Complex Regional Pain Syndrome (CRPS): A rare condition characterized by chronic pain, inflammation, and hypersensitivity, which can affect one limb after an injury or trauma.
  • Neuropathic Pain: Rarely, burning pain in the knee can be due to nerve damage or neuropathy, which might not have a clear association with knee extension but could be considered in the differential diagnosis if other causes are ruled out.