What are bursae in the context of joints?

Bursae are small, fluid-filled sacs that are located between bones and tendons, as well as between bones and other tissues in joints. Their primary function is to reduce friction and allow for smooth movement during joint motions, particularly in areas where tendons glide over bones. This cushioning effect helps to prevent irritation and inflammation of the surrounding tissues.

The other options describe different anatomical structures related to joints. Cartilaginous structures provide cushioning but are not bursae; they refer to cartilage, which offers support and flexibility in joint movement. Ligaments are indeed crucial for stabilizing joints, providing support by connecting bones to other bones, but they are distinct from bursae. Lastly, muscles that surround joints contribute to movement and stability as well, but they are not classified as bursae. Thus, the definition of bursae aligns perfectly with the first option, distinguishing them from other joint-related structures.