Sternocostal Joints

Sternocostal joints are the articulations between the costal cartilages of the true ribs (ribs 1–7) and the lateral borders of the sternum. These joints play a key role in stabilizing the anterior thoracic cage while allowing limited movement during respiration. The first sternocostal joint is a synchondrosis, whereas the remaining are synovial joints.

Location

These joints are located on the anterior thoracic wall, where the costal cartilages of ribs 1 to 7 meet the sternum. Each joint corresponds to the costal notch of the manubrium, body, or manubriosternal junction, depending on rib level.

Joint Types

• 1st sternocostal joint: Primary cartilaginous joint (synchondrosis); allows no movement
• 2nd–7th sternocostal joints: Synovial plane joints (diarthroses); permit slight gliding movements during respiration

Articulating Structures

• Medial end of the costal cartilage (ribs 1–7)
• Costal notches of the sternum (manubrium or body, depending on the rib)

Ligaments

The sternocostal joints are reinforced by surrounding ligaments:

• Radiate sternocostal ligaments: Fan-shaped fibers extending from the costal cartilage to the anterior and posterior surfaces of the sternum
• Intra-articular ligament (2nd rib): Connects the second costal cartilage to the fibrocartilaginous manubriosternal junction
• Capsular ligaments: Surround the synovial cavities, providing structural integrity

Movements

• 1st joint: Immobile (synchondrosis)
• 2nd–7th joints: Allow slight gliding movements during inspiration and expiration

Function

• Anchor the anterior ends of the true ribs to the sternum
• Permit expansion and recoil of the thoracic cage during respiration
• Stabilize the rib cage while allowing flexibility

Innervation

• Branches of the intercostal nerves (T1–T7)

Clinical Relevance

• Costochondritis: Inflammation of the costal cartilage and sternocostal joint, causing anterior chest pain
• Sternal dislocation: Trauma may displace costal cartilages at the sternum, especially in the 2nd or 3rd joints
• Arthritis: Sternocostal joints, especially the 2nd, may be involved in inflammatory arthropathies
• Surgical significance: Joints may be encountered or divided during sternotomy or thoracic surgeries