Knee Pain Differential Diagnosis

The following is a differential diagnosis for knee pain, categorized for clarity and emphasis on potential severity.

• Single Most Likely Diagnosis
  • Osteoarthritis: This is a common condition, especially in older adults, characterized by wear and tear of the joint cartilage, leading to pain, stiffness, and limited mobility. Its likelihood is high due to its prevalence and the broad range of symptoms that can be attributed to it.
• Other Likely Diagnoses
  • Ligament sprains (e.g., ACL, MCL, LCL): These are common injuries, especially in athletes or individuals who engage in physical activities that involve running, jumping, or quick changes in direction.
  • Meniscal tears: Tears in the cartilage of the knee joint can cause pain, locking, and catching sensations, and are common in both acute injuries and chronic conditions.
  • Tendinitis (e.g., patellar tendinitis): Inflammation of the tendons around the knee can cause pain, especially with activities like jumping or climbing stairs.
  • Bursitis: Inflammation of the fluid-filled sacs (bursae) that cushion the knee joint can cause pain and swelling.
• Do Not Miss Diagnoses
  • Septic arthritis: A bacterial infection within the joint, which is a medical emergency requiring prompt antibiotic treatment to prevent joint destruction.
  • Osteonecrosis (avascular necrosis): A condition where the bone tissue dies due to lack of blood supply, which can be caused by trauma, steroid use, or other factors.
  • Deep vein thrombosis (DVT): A blood clot in the deep veins of the leg, which can cause pain and swelling and has the potential to lead to a life-threatening pulmonary embolism if the clot breaks loose.
  • Fractures: While often obvious, some fractures (like stress fractures) may have subtle presentations and must not be overlooked.
• Rare Diagnoses
  • Rheumatoid arthritis: An autoimmune disorder that causes inflammation and pain in the joints, though it typically affects multiple joints simultaneously.
  • Gout or pseudogout: Forms of arthritis that cause sudden, severe joint pain, often accompanied by redness and swelling.
  • Osgood-Schlatter disease: A condition that causes knee pain in adolescents, particularly during growth spurts, due to inflammation of the patellar tendon at the tibial tubercle.
  • Neuropathic pain: Pain caused by nerve damage, which can be a result of various conditions, including diabetes or trauma.

Each of these diagnoses has a distinct set of symptoms and risk factors, and a thorough medical history, physical examination, and sometimes diagnostic tests are necessary to determine the correct diagnosis and appropriate treatment plan.