Objective. TO study the anatomy of the sternoclavicular joint, its discus a
nd its variations.
Design. Anatomical study (macroscopic dissection).
Background Textbooks on manual therapy give different descriptions of the m
ovements of this joint. These apparent contradictions could be due to poor
understanding of the anatomy of this joint resulting in ignoring specific m
ovement patterns under particular conditions.
Methods. Macroscopic dissection of 22 embalmed sternoclavicular joints.
Results. The sternoclavicular and the costoclavicular parts of the discus a
lways were quite distinct in orientation, thickness, surface and consistenc
y. The sternoclavicular part was attached to the dorso-cranial part of the
extremitas sternalis claviculae by a broad insertion in which several small
blood vessels are visible. This part is grossly vertical, thicker than the
lateral part and has a fibrous aspect. The costoclavicular part of the dis
cus is always thinner than the sternoclavicular part. Sometimes it is reduc
ed to a fine translucent pellet or is perforated. Subsynovial vascular arca
des run along the insertion of the discus on the joint capsule, both on ste
rnal and on clavicular sides. The costosternal articular surface can be div
ided into a sternal and a costal segment, separated by a vascular zone.
Conclusions. Findings suggest different functions of the distinct parts of
the joint. The smooth aspect of the lateral segment of the costosternal art
icular surface and of the costoclavicular part of the discus could be an ar
gument to consider a functionally distinct costoclavicular compartment. The
insertion of the discus on the clavicula strongly suggests that small move
ments take place between clavicula and discus and that the discus itself is
moved only when the increasing amplitude stretches this insertion. We hypo
thesise that all midrange movements take place between the convex inferior
edge of the clavicula and the costoclavicular part of he discus and that la
rger elevation depression and pro- and retraction movement take place, resp
ectively, between clavicula and discus or discus and sternum. In three spec
imens we observed a previously not described arterial ramus articularis ori
ginating from the left thyrocervical trunk.