Musculoskeletal strain or overuse injury: This is a common condition that can cause pain in the leg and groin area, especially if the pain changes location. It could be due to strain on the muscles or tendons from physical activity.

Herniated disc or lumbar radiculopathy: Pain from a herniated disc can radiate down the leg and into the groin, and the location of the pain can change depending on the position of the disc and the nerves affected.
Osteoarthritis of the hip: Hip arthritis can cause pain in the groin and leg, and the pain can change location as the condition progresses and affects different parts of the joint.
Trochanteric bursitis: Inflammation of the bursa over the hip can cause pain in the leg and groin area, and the location of the pain can shift as the bursa becomes more inflamed.

Aortic dissection or abdominal aortic aneurysm: These are life-threatening conditions that can cause severe, radiating pain in the leg and groin. Although less common, they are critical to diagnose early.
Deep vein thrombosis (DVT): A blood clot in the deep veins of the leg can cause pain and swelling, and in some cases, the pain can radiate to the groin area.
Testicular torsion (in males): This is a medical emergency that can cause severe pain in the groin and testicle, which can sometimes radiate down the leg.

Piriformis syndrome: This condition, where the piriformis muscle irritates the sciatic nerve, can cause pain in the leg and groin, but it is less common.
Peripheral artery disease (PAD): This condition involves narrowing of the arteries in the legs, which can cause pain in the legs and groin during exercise, but it is less likely to cause changing pain locations.
Neoplastic conditions (e.g., tumors): Although rare, tumors in the spine, hip, or leg can cause pain that changes location, and it's essential to consider them in the differential diagnosis, especially if other causes have been ruled out.