With one exception (the hyoid bone), every bone in the body is connected to or forms a joint with at least one other bone.

Joints perform two functions in the body:
1. they hold the skeletal bones together and
2. they allow the rigid skeleton some flexibility so that gross movements can occur.

Joints are points of union between bones. They may be more or less freely moveable, or fixed, allowing no movement whatsoever between the bones they join.

Functionally joints are classified as
1. immovable joints (= synarthroses:
   arthrose=joint, syn=together - bone stuck together),
2. slightly movable joints (= amphiarthroses:
   arthrose=joint, amphi=both - in between immovable and freely movable ),
3. freely movable joints (= diarthroses:
   arthrose=joint, dia=apart - bone apart, can move easily).

Their structural classification is based on the nature of the material comprising them.

Structurally joints are classified as
1. fibrous joints (joints held together by fibrous connective tissue and with no joint cavity),
2. cartilaginous joints (held together by cartilage, lacking a joint cavity)
3. synovial joints (in which the joint contains a synovial cavity).

Objectives - Name the three major structural types of joints and compare their structure and mobility. - Identify to which of these three structural types any joints in the body belong. - Classify synovial joints according to movement permitted. - Outline the structure and functions of bursae and tendon sheaths.