Joints are structures in which bones meet to either permit movement, or provide stability.There are plenty of them in our upper limbs.We’ve got the:sternoclavicular; the acromioclavicular; and the glenohumeral joints in the pectoral girdle; the elbow; the proximal and distal radioulnar joints in the forearm; the wrist joint; and the joints of the hand, which include the carpometacarpal, the intermetacarpal, the metacarpophalangeal, and interphalangeal joints.So let’s get acquainted with the first two of these joints!First up, there’s the sternoclavicular joint, which is the only bony articulation attaching the upper limb to the axial skeleton.It involves the clavicular notch of the manubrium, the medial end of the clavicle, and a small part of the first costal cartilage.It is a saddle synovial type of joint, named so because the manubrial articulating surface is concave and the clavicular articulating surface is convex, so they fit together the same way that a cowboy sits on his horse’s saddle.The joint has an articular disc that is firmly attached to the anterior and posterior fibrous joint capsule by the anterior and posterior sternoclavicular ligaments, as well as the interclavicular ligament.Like any other synovial joint, the articular surfaces of the sternoclavicular joint are covered by the fibrous joint’s capsule which has 4 ligamentous thickenings, simply called ligaments, lined internally by a thin layer of synovial membrane.The ligaments of the fibrous capsule are the anterior and the posterior sternoclavicular ligaments, which reinforce the joint capsule anteriorly and posteriorly; the interclavicular ligament which strengthens the sternoclavicular joint superiorly; and finally, there is the costoclavicular ligament, which anchors the inferior surface of the medial end of the clavicle to the 1st rib and its costal cartilage, providing stability to the sternoclavicular joint by limiting the elevation of the pectoral girdle.And second, there’s the acromioclavicular joint.It lies between the lateral end of the clavicle and the tip of the acromion of the scapula.It’s a plane type of synovial joint, meaning its articular surfaces are almost flat.Usually, there is a wedge-shaped articular disc between the articulating surfaces.The acromioclavicular joint is surrounded by a tough fibrous joint capsule with an internal synovial membrane that lines it.The acromioclavicular ligament strengthens the acromioclavicular joint superiorly, and extends from the acromion to the clavicle.The acromioclavicular ligament alone can’t hold this joint though, so it’s reinforced by other ligaments further away from the joint, which are known as extrinsic ligaments.First, there is the coracoclavicular ligament, which is in fact, two ligaments combined together to strongly anchor and fix the clavicle to the coracoid process.These are the conoid and the trapezoid ligament.

The conoid ligament is shaped, well, like a cone! Its base is attached to the conoid tubercle located at the inferior surface of the clavicle, and the apex attached inferiorly to the root of the coracoid process.And the trapezoid ligament, you guessed it, looks like a trapezoid.So no surprises here!

It’s attached to the superior surface of the coracoid process, from where it extends laterally to the trapezoid line on the inferior surface of the clavicle.Alright, before we wrap up, feel free to hit the pause button, and see if you can remember the four ligaments of the sternoclavicular and joint, and just two ligaments of the acromioclavicular joint.Alright, as a quick recap.

The sternoclavicular joint is a saddle synovial type of joint, and it’s the only bony articulation that attaches the upper limb to the axial skeleton.It has four ligaments: the anterior and the posterior sternoclavicular ligaments, which reinforce the joint capsule anteriorly and posteriorly; the interclavicular ligament which strengthens the sternoclavicular joint superiorly; and the costoclavicular ligament, which provides stability to the sternoclavicular joint by limiting the elevation of the pectoral girdle.The acromioclavicular joint is a plane type joint that lies between the lateral end of the clavicle and the tip of the acromion.It is supported by the acromioclavicular ligament and the coracoclavicular ligament which is made up of the conoid and trapezoid ligaments.