Sternoclavicular joint
The sternoclavicular joint (articulatio sternoclavicularis) performs a crucial biomechanical function: it is the only connection point between the free upper limb and the trunk.
Three main structures participate in the formation of the joint:
- Sternal end of the clavicle;
- Clavicular notch located on the manubrium of the sternum;
- Cartilage of the 1st rib (not the body of the rib, but specifically its cartilaginous part).
The articular capsule is loose and attaches strictly along the margins of the articulating surfaces. A distinctive feature of this joint is the presence of an articular disc within its cavity. It completely divides the joint cavity into two independent chambers, classifying the joint as complex.
Biomechanics
Based on the shape of the articular surfaces and range of motion, it is a multiaxial joint (operating around three axes). The following movements are possible in it:
- Elevation and depression of the clavicle;
- Protraction (forward movement) and retraction (backward movement) of the clavicle;
- Rotation of the clavicle around its longitudinal axis.
Ligamentous apparatus of the sternoclavicular joint
The loose joint capsule is reliably reinforced by a robust complex of ligaments that limit excessive mobility and protect the joint from dislocations:
- Anterior and posterior sternoclavicular ligaments (lig. sternoclaviculare anterius et posterius) — blend into the capsule from the respective sides;
- Interclavicular ligament (lig. interclaviculare) — stretched between the medial ends of the right and left clavicles, passing over the manubrium of the sternum;
- Costoclavicular ligament (lig. costoclaviculare) — a strong band fixing the clavicle to the cartilage of the 1st rib.
Acromioclavicular joint
The acromioclavicular joint (articulatio acromioclavicularis) is an articulation between the scapula and the clavicle.
The articular surfaces are formed by the acromion of the scapula and the lateral end of the clavicle. Unlike the previous joint, the capsule here is thin, although it attaches similarly — along the margins of the articular surfaces. An articular disc may sometimes be present within the cavity of this joint, but its presence is not a constant feature.
Functions and ligaments
The range of motion in this joint is small, but it is critically important for ensuring coordinated rotation of the scapula along with the clavicle during arm elevation.
The joint is supported by the following ligamentous apparatus:
- Acromioclavicular ligament (lig. acromioclaviculare) — reinforces the capsule superiorly.
- Coracoclavicular ligament (lig. coracoclaviculare) — acts as a crucial stabilizer of the joint. It consists of two anatomical parts: the trapezoid (lig. trapezoideum) and conoid (lig. conicum) ligaments.
Briefly: answers to topical questions
What type of joint is the sternoclavicular joint according to its shape and biomechanics?
According to its biomechanics, the sternoclavicular joint is a multiaxial joint that allows movements around three axes: elevation and depression, protraction and retraction, and rotation of the clavicle. The joint cavity contains an articular disc dividing it into two chambers, making it a complex joint.
What is the shape-based joint type of the acromioclavicular joint?
The provided study materials do not give a direct classification of the acromioclavicular joint based on the shape of its articular surfaces. It is only known that its articular surfaces are the acromion of the scapula and the clavicle, the capsule is thin, and an articular disc is sometimes present in the joint.
Which ligaments belong to the proper ligaments of the scapula?
Among the proper ligaments of the scapula, the materials mention the superior transverse scapular ligament. It forms the ligamentous apparatus of the scapular region; the suprascapular nerve passes beneath it, whereas the suprascapular artery runs above this ligament.
What are the blood supply sources of the acromioclavicular joint?
The provided study materials indicate the participation of the clavicular branch of the thoracoacromial artery in the vascularization of the acromioclavicular joint. Other sources of blood supply to this joint are not specified.
To memorize the clavicular ligaments near the sternum, use the directional rule: forward/backward (sternoclavicular), downward to the rib (costoclavicular), and laterally to the other clavicle (interclavicular).
Class and exam questions
Why is the sternoclavicular joint called complex?
The joint is called complex because a cartilaginous articular disc is located inside its capsule. It divides the single joint cavity into two separate chambers.
Which joint is the only bony connection between the arm and the trunk?
This function is performed exclusively by the sternoclavicular joint (articulatio sternoclavicularis).
What bundles make up the coracoclavicular ligament?
This crucial stabilizer of the acromioclavicular joint consists of two parts: the trapezoid ligament (trapezoideum) and the conoid ligament (conicum).
What else to study on this topic
- Axes of rotation and range of motion in the sternoclavicular joint
- The role of the articular disc in dividing the joint cavity
- Anatomical differences between the trapezoid and conoid ligaments
- Synchronization of clavicular and scapular movements
Study the complete topic in the Anatomy course
This is a summary. The course covers everything tested in classes and exams.
- Complete study guide on "Joints of the Pectoral Girdle Bones" and 1,363 more pages of the subject
- Assignments and quizzes after every topic — just like in a colloquium
- AI tutor answers questions on the topic anytime
- 295 video lessons by subject
Other topics in the "Arthrology" section
Free video lessons: AnatomyShort lessons with study notes — no registration required.
Prepared by WhiteCoat Pro faculty in accordance with the medical school curriculum. For educational purposes only.