Dr. William Sutherland formulated many of the concepts  that  form the basis  for modern CranioSacral therapy. The field of study based on Sutherland's work is called Cranio Osteopathy.

Dr. John Upledger refined the original concepts and developed the modern field of CranioSacral therapy. Dr. Upledger  researched and introduced many original concepts which greatly expands therapeutic technique based upon the CranioSacral system.

A simplified description of the CranioSacral system is presented below.

The CranioSacral system includes the cranium, and the spine which terminates in the sacrum. The bones of the cranium and the vertebra of the spine form the protective shield for the brain and spinal cord.

There is a membrane that covers the inside of the cranium and the spinal canal (Dural membrane). The Dural membrane  forms an enclosed system that contains other membranes, the brain, spinal cord, and Cerebrospinal fluid.

Cerebrospinal fluid is produced and absorbed within the Dural membrane enclosure causing increasing and decreasing fluid pressure on a periodic basis. These pressure changes produce small movements  in the bones surrounding  the Dural membrane and other parts of the body. The therapist can feel these  periodic  movements (the CranioSacral rhythm) and use this information to assist in determining where problems may exist within the system.