Piriformis Syndrome: This condition is characterized by compression of the sciatic nerve by the piriformis muscle, leading to sharp pain in the buttocks that radiates down the thigh. The piriformis muscle runs from the base of the spine to the thighbone, and when it compresses the sciatic nerve, it can cause pain, numbness, and tingling in the buttocks and thigh.

Sciatica: This is a common condition caused by irritation of the sciatic nerve, which runs from the lower back down to the legs. Sciatica can cause sharp pain in the buttocks that radiates down the thigh, as well as numbness, tingling, and weakness in the leg.
Lumbar Herniated Disc: A herniated disc in the lumbar spine can compress the sciatic nerve, causing sharp pain in the buttocks that radiates down the thigh.
Trochanteric Bursitis: This is inflammation of the bursa that cushions the tendons and bones near the hip joint. It can cause sharp pain in the buttocks that radiates down the thigh.

Cauda Equina Syndrome: This is a serious condition that occurs when the nerves in the spinal canal are compressed, causing pain, numbness, and weakness in the legs, as well as loss of bladder and bowel control. It requires immediate medical attention.
Deep Vein Thrombosis (DVT): A blood clot in the deep veins of the leg can cause sharp pain in the buttocks and thigh, as well as swelling and redness.
Osteonecrosis of the Femoral Head: This is a condition where the blood supply to the femoral head is disrupted, causing the bone to die. It can cause sharp pain in the buttocks and thigh.

Sacroiliitis: This is inflammation of the sacroiliac joint, which can cause sharp pain in the buttocks that radiates down the thigh.
Ischiogluteal Bursitis: This is inflammation of the bursa that cushions the tendons and bones near the ischial tuberosity. It can cause sharp pain in the buttocks that radiates down the thigh.
Neoplastic Processes: Tumors in the spine, pelvis, or soft tissues can cause sharp pain in the buttocks that radiates down the thigh.