MSFinals-2600

A 75-year-old male presents with bilateral buttock pain that radiates through his thighs and calves. The pain worsens with standing and walking, limiting his ability to walk for more than 10 minutes or 2 to 3 blocks. However, the pain is relieved by sitting or forward flexion of the spine. There is no history of bladder or bowel dysfunction, and motor and sensory neurological examination of the lower limbs is normal. What is the most probable cause of these symptoms?