Description
A top sirloin is composed of two main parts, the sirloin cap (biceps femoris) and the center sirloin (gluteus profundus, gluteus accessorius, and gluteus medius). The gluteus profundus and the gluteus accessorius are small muscles and can be considered accessory muscles. A trimmed boneless top sirloin butt consists of just the center sirloin with the accessory muscles excluded. The center sirloin is then further trimmed of excess fat.