Rami is the plural of “ramus,” a Latin word that simply means “branch.” In anatomy, it refers to any structure that branches off from a larger one, whether that’s a bone, a nerve, or a blood vessel. You’ll most commonly encounter the term in three contexts: the branching portions of the jawbone, the bony extensions of the pelvis, and the divisions of spinal nerves.
Rami in Bone: The Jaw and Pelvis
The two skeletal structures most often described using “ramus” or “rami” are the mandible (jawbone) and the pubic bone.
The Mandibular Ramus
Your jawbone isn’t one simple curve. On each side, a broad, roughly square-shaped plate of bone extends upward and backward from behind the teeth. This is the mandibular ramus. At its top, the ramus splits into two projections: the coronoid process toward the front, and the condylar process toward the back. The condylar process forms the actual joint where your jaw meets your skull, just in front of your ear. The coronoid process serves as an anchor point for the temporalis muscle, one of the main muscles you use to chew.
The masseter, another powerful chewing muscle, attaches directly to the outer surface of the ramus. A third muscle, the medial pterygoid, attaches to the inner surface. Together, these muscles use the ramus as a lever to open, close, and shift the jaw side to side. Fractures of the mandibular ramus can happen from high-impact trauma and are one of several recognized categories of jaw fracture that surgeons classify by location.
The Pubic Rami
In your pelvis, two bony extensions branch off from the pubic bone on each side. The superior pubic ramus passes outward and upward to connect with the ilium (the large, wing-shaped bone you feel at your hip). The inferior pubic ramus extends downward and joins with a portion of the ischium, the bone you sit on. Together, these rami frame a large opening called the obturator foramen, and the inferior pubic rami from both sides form the pubic arch at the front of the pelvis.
If you’ve heard the term “rami” from a doctor, there’s a good chance it was in the context of a pubic rami fracture. These fractures are among the most common pelvic injuries, particularly in older adults with osteoporosis, where even a minor fall or routine activity can cause a break. In younger people, they typically result from car accidents, falls from height, or high-impact sports. Symptoms include pain in the groin, hip, or lower back that worsens with walking, along with possible numbness or tingling in the groin or legs and difficulty standing. Most pubic rami fractures heal in 8 to 12 weeks, though more severe breaks or those accompanied by other injuries can take longer.
Rami in Nerves: Spinal Nerve Branches
Every spinal nerve that exits your spinal cord splits into two main branches, each called a ramus. The dorsal (posterior) ramus curves backward to supply the skin and muscles of your back. The ventral (anterior) ramus runs forward and sideways to supply the muscles and skin of the front and sides of your trunk, your arms, and your legs. The ventral rami are generally larger because they serve a much bigger territory, including all four limbs.
Rami Communicantes
A second type of nerve ramus is smaller and more specialized. Rami communicantes are tiny connecting branches between the spinal nerves and the sympathetic chain, a paired line of nerve clusters running along both sides of your spine. These branches are part of the autonomic nervous system, the network that controls involuntary functions like heart rate, blood vessel diameter, and sweating.
There are two varieties, named for their appearance. White rami communicantes look pale because their nerve fibers are coated in myelin, a fatty insulating layer. They carry outgoing signals from the spinal cord to the sympathetic chain and exist only at spinal levels from the upper chest down to the lower back (roughly T1 through L2). Gray rami communicantes look darker because their fibers lack that myelin coating. They carry signals back from the sympathetic chain to the spinal nerves for distribution throughout the body. Every spinal nerve has a gray ramus, which is why sympathetic effects like sweating and blood vessel constriction can occur essentially anywhere in the body, not just in the chest and lower back where the white rami originate.
How Rami Come Up in Pain Treatment
If you’re dealing with chronic back or neck pain, you may hear about a procedure called a medial branch block. The medial branch is a small offshoot of the dorsal ramus that supplies sensation to the facet joints, the small joints connecting each vertebra to the next. During the procedure, a doctor uses X-ray guidance to place a needle near the medial branch and delivers numbing medication. If the block provides short-term relief, confirming that the medial branch is carrying the pain signal, a follow-up procedure called radiofrequency ablation can disable that nerve branch for months to years at a time.
This is a practical example of why the branching pattern of rami matters. Because nerves divide into predictable branches at each spinal level, doctors can target a single small ramus to interrupt pain signals from a specific joint without affecting sensation or movement elsewhere.