No bone
A typical synovial joint has a joint capsule, a synovial membrane, synovial fluid, a joint cavity, and articular cartilage. A joint capsule surrounds the joint, supporting and stabilizing it. The synovial membrane is within the joint capsule. This membrane closely surrounds the joint and forms a joint cavity. The synovial membrane secretes synovial fluid that lubricates the articular surfaces of the joint. In some joints, the synovial membrane extends outside the joint capsule to form a bursa. The bursa cushions the joint. Bursae are in the knee, elbow, shoulder, and hip. Articular cartilage covers the articular surfaces of synovial joints to prevent excess wear and tear as they move against each other.
All synovial joints contain a joint cavity. Synovial joints differ from the other joints: Fibrous and cartilaginous joints. Synovial is different because of its structure, and includes several parts including a joint cavity.
That is the bursa in your synovial joint. Bursa lines with the synovial membrane and contains synovial fluid that is used to lubricate the joint when there's movement.
synovial cavity
synovial joints have synovial cavities
joint cavity
Synovial joints have a fibrous articular capsule lined with synovial membrane surrounding a joint cavity.
Synovial Joints
a joint cavity, the potential space bounded by the synovial membrane and articular cartilages of all synovial joints. Normally, the articular cavity contains only sufficient synovial fluid to lubricate the internal surfaces.
The Joint Cavity is the space or scientifically a 'potential' space filled with synovial fluid. The function of this fuild is to reduce friction by lubricationg the joint.
Synovial
I this its the following: Bursae - located between skin and bones, tendons and bones, muscles and bones, or ligaments and bones - Main function: reduce friction between joints Joint Capsule - surrounds a synovial joint and encloses the synovial cavity - Main function: unite the articulating bones and reduce friction via production of synovial fluid