Differential Diagnosis for Femoral Pain with Benign MRI

Single Most Likely Diagnosis

• Chronic Tendinopathy or Overuse Injury: Given the long-standing nature of the pain since the patient was 12, and the exacerbation with walking and cold weather, a chronic tendinopathy or overuse injury of the muscles or tendons around the femur is a plausible explanation. The intermittent muscle spasms in the anterior thigh further support this diagnosis.

Other Likely Diagnoses

• Femoral Neuropathy: This condition could cause pain, especially if the femoral nerve is irritated or compressed, leading to pain in the anterior thigh and potentially muscle spasms.
• Stress Fracture: Although the MRI is reported as benign, stress fractures can sometimes be missed on initial imaging. The worsening of pain with walking and in cold weather could be indicative of a stress fracture.
• Referred Pain from the Lower Back: Pain from the lower back, such as from a herniated disc or facet joint syndrome, can refer to the thigh and could be exacerbated by walking and changes in weather.

Do Not Miss Diagnoses

• Osteosarcoma or Other Bone Cancers: Although rare, bone cancers can present with persistent pain and should be considered, especially if there's a history of pain that has been ongoing since a young age.
• Avascular Necrosis of the Femoral Head: This condition can cause hip and thigh pain and is a significant diagnosis not to miss due to its potential for severe outcomes if left untreated.
• Infection (Osteomyelitis): Chronic infection of the bone can cause persistent pain and should be considered, especially if there are any systemic symptoms or risk factors for infection.

Rare Diagnoses

• Piriformis Syndrome: Although more commonly associated with sciatic pain, in rare cases, the piriformis muscle can compress the femoral nerve, leading to thigh pain.
• Peripheral Artery Disease (PAD): PAD can cause claudication pain in the thighs when walking, which improves with rest. This would be an unusual diagnosis in a younger patient without significant vascular risk factors but should be considered in the differential.
• Chronic Regional Pain Syndrome (CRPS): This condition can cause persistent, severe pain and could be a consideration if other diagnoses are ruled out and the pain is disproportionate to the expected pathology.