A ligament is a tough band of connective tissue that connects bones to other bones at a joint. They play a crucial role in stabilizing joints and allowing for smooth movement. For example, the ACL (anterior cruciate ligament) in the knee helps maintain stability during activities like running and jumping. Ligaments are made up of collagen fibers, which give them strength and flexibility. Unlike muscles, ligaments do not contract; instead, they provide support and limit the range of motion to prevent injuries. When ligaments are stretched too far, they can tear, leading to conditions like a sprain.