Costovertebral articulations
The posterior section of the thoracic cage is characterized by high mobility due to paired combined joints at each level.
- Costovertebral joint (articulatio capitis costae). Formed by the articular surfaces of the rib heads and corresponding costal facets on the vertebral bodies. The articular capsule is tightly fixed strictly along the edge of the cartilaginous surfaces. For additional stability, this complex is reinforced by the intra-articular ligament of the head of the rib (intraarticular lig. capitis costae) and the radiate ligament (lig. capitis costae radiatum).
- Costotransverse joint (articulatio costotransversaria). This articulation is located between the rib tubercle and the transverse process of the corresponding vertebra. Its stability is supported by a robust ligamentous apparatus including the superior, lateral, and proper costotransverse ligaments (lig. costotransversarium superius, laterale et proprium).
The coordinated work of these two articulations forms a single axis around which the rib performs rotational movements during inspiration and expiration.
Anterior connections: ribs and sternum
Anteriorly, the ribs transition into cartilaginous tissue and form connections with entirely different biomechanics.
- Costochondral joints (articulationes costochondrales). These are areas where the bony part of the rib transitions into the cartilaginous part. They are completely immobile.
- Sternocostal joints (articulationes sternocostales). Characteristic of ribs II–VII. These are true synovial joints that are securely reinforced externally by radiate sternocostal ligaments (ligg. sternocostalia radiata). An important exception is the cartilage of the first rib, which forms a continuous connection with the sternum — a synchondrosis.
- Interchondral joints (articulationes interchondrales). Found between the cartilaginous ends of the false ribs (VII to X).
The lowermost ribs (XI and XII) do not reach the sternum at all. They remain free, and their anterior ends are embedded directly into the musculature of the abdominal wall.
Intrinsic ligaments and age-related changes of the sternum
The sternum itself also has a complex structure and a fixation system for its parts. In the area where the manubrium of the sternum transitions into its body, there is an intra-articular ligament (lig. sterni intraarticulare). On its external surface, the bone is covered by a dense network of radiate sternal ligaments (ligg. sterni radiata).
With age, the cartilaginous layers between individual fragments of the sternum undergo ossification. As a result, synostoses are formed — solid bony fusions turning the sternum into a single monolithic bone.
Briefly: answers to topical questions
What articular surfaces form the costovertebral joint for ribs II–X?
The costovertebral joint for ribs II–X is formed by the articular surface of the rib head and the costal demifacets of the bodies of two adjacent vertebrae.
- Articular surface of the rib head (facies articularis capitis costae) — divided by the crest of the head of the rib (crista capitis costae) into upper (smaller) and lower (larger) parts.
- Superior and inferior costal demifacets (fovea costalis superior and fovea costalis inferior) — located on the bodies of adjacent thoracic vertebrae. The upper part of the head articulates with the inferior demifacet of the vertebra above, and the lower part with the superior demifacet of the vertebra below.
On which vertebrae is the costotransverse joint absent?
The costotransverse joint is absent on the eleventh and twelfth thoracic vertebrae (T₁₁–T₁₂). The transverse processes of these vertebrae lack costal facets (fovea costalis processus transversi) because their corresponding XI and XII ribs have a simpler structure and lack the costal tubercle (tuberculum costae). Therefore, articulation with the transverse processes does not occur in these vertebrae.
What is the anatomical name of the connection between the manubrium and the body of the sternum?
Anatomically, the connection between the manubrium and the body of the sternum is called the manubriosternal symphysis (symphysis manubriosternalis). This articulation forms an obtuse sternal angle (angulus sterni) facing posteriorly, which is easily palpable on the anterior chest wall. Located at this connection is the intra-articular ligament of the sternum (lig. sterni intraarticulare). With age, the cartilaginous layers between parts of the sternum may ossify, forming synostoses.
What forms the costal margin?
The costal margin (arcus costalis) is formed by the cartilages of the VII, VIII, IX, and X ribs. The formation of this structure involves the so-called false ribs (costae spuriae — pairs VIII–X), whose cartilages do not reach the sternum directly, but successively connect to the cartilages of the ribs above. The convergence of the right and left costal margins at the xiphoid process forms the infrasternal angle (angulus infrasternalis).
To remember the ligaments of the costal tubercle, use the formula "SLP": Superior, Lateral, Proper (proprium) — these are the lig. costotransversarium superius, laterale et proprium.
Class and exam questions
Which joints are responsible for thoracic cage excursion during respiration?
Rotation of the ribs during breathing is ensured by the combined action of the costovertebral joint and the costotransverse joint.
How does the connection of the first rib with the sternum differ from the other true ribs?
The first rib articulates with the sternum via a synchondrosis (cartilaginous fusion), whereas ribs II through VII form mobile synovial sternocostal joints.
Where do the eleventh and twelfth ribs terminate?
They belong to the floating ribs, have no connections with the sternum or other ribs anteriorly, and terminate directly in the abdominal muscles.
What else to study on this topic
- Structure of the intra-articular ligaments of the rib head
- Biomechanics of sternocostal joints in true ribs
- Formation and anatomy of interchondral connections
- Age-related sternal synostoses
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