Differential Diagnosis for Knee and Foot Pain

The patient presents with knee pain that resolved and was followed by pain on the outer part of the left foot. Here's a structured approach to the differential diagnosis:

• Single Most Likely Diagnosis
  • Referred pain or peripheral neuropathy: The initial knee pain that resolved and then presented as foot pain could be indicative of a neuropathic issue where the pain is referred. This could be due to various reasons such as nerve compression or damage.
• Other Likely Diagnoses
  • Tendinitis or ligament sprain: The transition from knee to foot pain could indicate a problem with the tendons or ligaments that connect these areas, possibly due to overuse or injury.
  • Osteoarthritis: Although the pain moved from the knee to the foot, osteoarthritis could be a consideration, especially if the patient has a history of joint issues. The pain in the foot could be related to altered gait mechanics due to knee arthritis.
  • Plantar fasciitis: This condition causes pain on the bottom of the heel and can sometimes radiate to the outer part of the foot, which aligns with the patient's current symptoms.
• Do Not Miss Diagnoses
  • Deep vein thrombosis (DVT): Although less common, DVT can cause pain in the leg that might initially be perceived as knee pain and then seem to move as the condition progresses. It's crucial to rule out DVT due to its potential for severe complications.
  • Peripheral artery disease (PAD): This condition can cause intermittent claudication, which is pain in the legs or feet that occurs with walking and other exercises, possibly mimicking the patient's symptoms.
  • Infection or osteomyelitis: Infections in the bone or soft tissue can cause pain that seems to move or change location as the infection spreads or responds to the body's immune response.
• Rare Diagnoses
  • Complex regional pain syndrome (CRPS): A chronic pain condition that can cause severe pain, usually in an arm or leg, after an injury or trauma. The pain can seem to move or change over time.
  • Erythromelalgia: A disorder that causes burning pain, heat, and redness in the hands and feet, which could potentially be confused with the patient's symptoms if the presentation is atypical.

Each of these diagnoses should be considered in the context of a thorough patient history, physical examination, and potentially, diagnostic tests to determine the underlying cause of the patient's symptoms.