Differential Diagnosis for Left Upper Thigh Pain Above the Knees

Single Most Likely Diagnosis

• Lumbar Radiculopathy: This condition, often resulting from a herniated disk or spinal stenosis in the lower back, can cause pain that radiates down into the thigh. The pain pattern can vary but often affects the upper thigh, especially if the nerve root involved is L2 or L3, which can cause pain in the anterior or lateral thigh.

Other Likely Diagnoses

• Trochanteric Bursitis: Inflammation of the bursa over the greater trochanter of the femur can cause pain on the outer aspect of the thigh, which might be perceived as being above the knee.
• Meralgia Paresthetica: This condition involves compression of the lateral femoral cutaneous nerve, leading to pain, numbness, or tingling in the outer part of the thigh, which could be mistaken for pain above the knee.
• Piriformis Syndrome: Although more commonly associated with pain in the buttock and down the back of the leg, in some cases, the pain can radiate to the upper thigh, especially if the piriformis muscle compresses nerves that supply the thigh.

Do Not Miss Diagnoses

• Abdominal Aortic Aneurysm: While less common, an abdominal aortic aneurysm can cause lower back pain that radiates to the groin or thighs due to the proximity of the aorta to the lumbar spine and nerves. This is a medical emergency.
• Osteonecrosis of the Femoral Head: Pain from osteonecrosis can initially present in the groin, thigh, or knee due to referred pain. Early diagnosis is crucial to prevent collapse of the femoral head.
• Spinal Infection or Tumor: Infections (like osteomyelitis or discitis) or tumors of the spine can cause back pain that radiates to the thighs. These conditions require prompt diagnosis and treatment to prevent serious complications.

Rare Diagnoses

• Neurogenic Tumors: Rarely, tumors arising from the nerves (such as neurofibromas or schwannomas) can cause pain in the distribution of the affected nerve, potentially leading to thigh pain.
• Chronic Compartment Syndrome: This condition, more common in athletes, involves increased pressure within a muscle compartment, leading to pain, usually after exercise. It's less likely to cause isolated upper thigh pain above the knee but could be considered in the differential diagnosis of exertional thigh pain.