Articulations of the Thorax
- Sternoclavicular joint: This saddle synovial joint contains an articular disc and strong ligaments. It is the only direct bony connection between the upper limb and axial skeleton.
- Sternocostal joints: The first sternocostal joint is a synchondrosis, whereas joints 2 through 7 are synovial plane joints. Their small gliding movements combine with rib rotation during respiration.
- A synovial joint has a lubricated cavity, a plane joint mainly glides, a saddle joint moves in more than one plane, an articular disc is fibrocartilage inside a joint, and a synchondrosis is a cartilage joint.
- Costochondral joints: Hyaline cartilage unites each rib with its costal cartilage. These joints permit little movement but provide an elastic continuation of the rib.
- Manubriosternal joint: This symphysis forms the sternal angle. It may permit slight movement as the ribs elevate and is a key surface landmark for thoracic anatomy.
- Xiphisternal joint: Usually a synchondrosis, this joint can ossify with age. It marks the junction between the body and xiphoid process.
- A symphysis is a fibrocartilage joint, and ossify means to become bone or more bone-like over time.
- Costovertebral joints: Rib heads articulate with vertebral bodies and adjacent intervertebral discs. These synovial joints allow the rib shafts to move during inspiration and expiration.
- Costotransverse joints: Rib tubercles articulate with transverse processes. Ribs 11 and 12 lack these joints, which helps explain their greater anterior mobility.
- Interchondral joints: Adjacent costal cartilages, commonly 6 through 9 or 10, may connect through synovial joints. They help stabilize the costal margin while allowing limited expansion.
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