Sagittal section through the clivus of the skull
demonstrating the location of the sphenooccipital
synchondrosis in an infant.
A synchondrosis (plural: synchondroses) is a type of cartilaginous joint characterized by a plate of hyaline cartilage that joins two bones. It is also known as a “primary cartilaginous joint”.
Since a synchondrosis practically has no movement, it is classified as a synarthrosis (plural: synarthroses) an immovable joint. All synchondroses are synarthrotic.
Because of the way bones mature, there are many skeletal synchondroses present while the individual matures, an important group of synchondroses are those of growth plates in long bones at the junction of the epiphysis and the body or shaft of the bone. These disappear when the individual reaches full skeletal maturity.
In the older individual there are a few synchondroses, one of them is found at the joint between the first rib and the sternum, others are found at the costochondral joint, the joint between the ribs and the costal cartilage.
There may be some synchondroses found in areas of skeletal anomalies, like the os acromiale, and tarsal coalitions.
Etymology: The word “synchondrosis” derives from the following medical terminology components: The Greek prefix [σύν] (sýn) meaning “along, with, or plus”, the Greek root term [χόνδρος] from [χόνδρος αρθρώσεων] (chóndros arthróseon), and the suffix [-osis], also Greek, meaning “condition”, “state of” or “many”. The term “synchondrosis” can be loosely interpreted as a “condition with cartilage”.
Sources:
1. “Gray’s Anatomy” Henry Gray, 1918
2. "Tratado de Anatomia Humana" Testut et Latarjet 8th Ed. 1931 Salvat Editores, Spain
3. "Gray's Anatomy" 38th British Ed. Churchill Livingstone 1995
4. "The Origin of Medical Terms" Skinner, HA 1970 Hafner Publishing Co.
Image modified from the original by Henry VanDyke Carter, MD. in the book "Grays's Anatomy" by Henry Gray FRS. Public domain