Lumbar Radiculopathy: This condition, often due to a herniated disc, can cause pain to radiate down the leg, typically following a dermatomal pattern. The pain can be referred to the hip and leg due to nerve root irritation, making it a common cause of such symptoms.

Trochanteric Bursitis: Inflammation of the bursa over the greater trochanter of the femur can cause pain on the outer aspect of the hip and thigh, which may radiate down the leg.
Piriformis Syndrome: The piriformis muscle can compress the sciatic nerve, leading to pain in the buttock and referred pain down the back of the leg.
Osteoarthritis of the Hip: Degenerative joint disease can cause hip pain that may radiate down the leg, especially with weight-bearing activities.
Sacroiliitis: Inflammation of the sacroiliac joint can cause pain in the lower back, hip, and leg, often on one side.

Abdominal Aortic Aneurysm: Although less common, a ruptured abdominal aortic aneurysm can cause severe back and abdominal pain that may radiate to the hip and leg, and is a medical emergency.
Ectopic Pregnancy: In women of childbearing age, an ectopic pregnancy can cause abdominal pain that may radiate to the hip and leg, and requires immediate medical attention.
Appendicitis: In some cases, especially if the appendix is located near the hip, appendicitis can cause pain that is referred to the hip and leg.

Neoplastic Processes: Tumors in the spine, hip, or abdominal cavity can cause referred pain to the hip and leg, though these are less common causes.
Inflammatory Arthropathies: Conditions like rheumatoid arthritis or ankylosing spondylitis can cause hip and leg pain, but the presentation is usually more systemic and involves multiple joints.
Neurological Disorders: Certain neurological conditions, such as multiple sclerosis or peripheral neuropathy, can cause pain in the hip and leg, but these typically have other distinctive symptoms and signs.