What Are SOT Blocks and How Do They Work? A Complete Patient Guide

Patients who come to Pura Vida Chiropractic for the first time sometimes have a moment of mild confusion when I bring out the blocks. They came expecting a spinal adjustment — something they can feel, with a pop or a click that signals something was done. Instead, I place two wedge-shaped foam or rubber blocks under their hips and ask them to lie still for a few minutes.

"That's it?" is a common response.

Not quite. What those blocks are doing during those minutes is considerably more sophisticated than it looks. Let me explain the history behind them, the principles that make them work, and what you can expect when they're part of your care.

The Man Behind the Technique: Dr. M.B. DeJarnette

Sacro Occipital Technique — SOT — was developed by Dr. Major Bertrand DeJarnette, a chiropractor and osteopath who practiced and researched prolifically from the 1920s through the 1980s. DeJarnette was a remarkable figure: a meticulous clinician and a rigorous self-experimenter who reportedly used himself as a research subject for many of his treatment approaches.

His central insight — arrived at through years of observation — was that the pelvis and the skull are not independent structures. They are the two anchoring points of the dural tube (the membrane that surrounds the brain and spinal cord), and they move together in a rhythmic, reciprocal relationship that he called the craniosacral respiratory mechanism.

DeJarnette also recognized that most spinal problems originate in the pelvis, not in the specific area where pain is felt. A lumbar disc herniation, for instance, rarely begins with the disc. It begins with a foundational imbalance in the sacroiliac joint that alters loading mechanics through the lumbar spine over time, until the disc eventually gives way under accumulated stress.

His response to this insight was methodical: develop a classification system that identified the type of pelvic imbalance present, and a treatment system that corrected it without adding more force to an already stressed structure.

The blocks were his solution.

What the Blocks Look Like and the Basic Principle

SOT blocks are wedge-shaped pieces of dense foam or rubber, roughly the size of a thick paperback book. They are placed under the bony landmarks of the pelvis — specifically the iliac crests and the sacrum — in precise positions that vary depending on the type of correction being made.

The fundamental principle is this: instead of the chiropractor applying an external force to move the pelvis, the blocks harness gravity and the patient's own body weight to create a sustained, gentle corrective force. The pelvis, resting over the blocks in a specific position, is gently separated or supported in a way that allows the sacroiliac ligaments and muscles to relax and the joint to normalize its position.

This works because of a property of soft tissue called creep — the slow deformation of connective tissue under sustained low load. A brief, forceful thrust (the kind used in traditional spinal manipulation) moves bone quickly but may not allow the ligaments and muscles to follow. A sustained gentle load, applied over two to five minutes, allows the connective tissue to actually remodel its tension and hold the correction.

The blocks are not passive. During the time they are in place, the body is actively responding. The practitioner may periodically assess what is happening through palpation and adjust the block position to follow the correction as it progresses.

The Three SOT Categories: A Quick Overview

DeJarnette classified sacropelvic problems into three categories based on severity and the structures involved. Understanding these categories helps explain why block placement looks different from visit to visit.

Category I involves a basic sacroiliac joint imbalance — one side of the pelvis is slightly higher or rotated relative to the other. This is the most common presentation and the mildest in terms of structural stress. Block placement in Category I is designed to gently balance the two iliac bones and normalize SI joint position.

Category II involves sprain of the sacroiliac ligaments with resulting dural tube tension. This is a more significant finding. The SI ligaments are stretched or partially disrupted, and the dural tube — which attaches to the sacrum — is under tension as a result. Category II has specific clinical tests (including the arm fossa test) and requires a different, more specific block placement that must not further stress the ligamentous complex. Forceful manipulation in a Category II patient typically makes things worse, which is why the gentleness of blocks is particularly valuable.

Category III involves disc involvement — usually a lumbar disc that is under pressure or has partially herniated. Block placement in Category III is the most specific and is often combined with additional techniques including lumbar traction, cold laser therapy, or decompression work at our clinic.

The doctor determines which category applies through a standardized assessment that includes postural observation, leg length analysis, muscle testing, and specific orthopedic tests. The category can change as healing progresses — most patients move through Category II or III into Category I and eventually out of active care.

What the Patient Experiences

For most people, lying on the blocks is comfortable and even pleasant. The initial block placement may feel slightly unusual — a subtle sense of the pelvis being gently stretched. Within the first minute or two, most patients notice the sensation changing as the tissues begin to release: a warmth in the pelvis, a decrease in the sense of tension, sometimes a spontaneous deep breath.

The practitioner will check in during the procedure, sometimes adjusting block position to follow the correction. Sessions with blocks typically last five to ten minutes for the blocking portion, followed by additional work in the upper spine and cranium as needed.

Some patients — particularly those in Category II with significant SI ligament involvement — feel significant relief after the first session. Others feel a mild achiness for a day or two as the pelvis adjusts to a new position before feeling better. Both responses are normal.

Why Blocks Achieve What Manipulation Alone Often Cannot

The sacroiliac joint is one of the most heavily ligamentous joints in the body. Its stability depends on an intricate web of ligaments that, when sprained, do not benefit from repeated forceful loading. Yet many standard chiropractic and physical therapy protocols involve exactly that: repeated manipulation, mobilization, and exercise that loads the injured ligament complex.

Blocks respect the biology. They deliver a corrective force without adding to the mechanical stress on compromised tissues. They allow the body's own healing mechanisms — which are working constantly — to operate in a supported, favorable mechanical environment.

In my twenty-three years of practice, I've seen patients come to me after years of unsuccessful care elsewhere — multiple chiropractic techniques, physical therapy, injections — for low back and SI joint pain. When the correct category is identified and blocks are used appropriately, results that seemed elusive often become straightforward. Not because the blocks are magic, but because they're finally treating the right problem in the right way.

What to Expect in a Typical SOT Session at Pura Vida Chiropractic

A typical session begins with a brief assessment — posture, leg length, relevant orthopedic tests — to determine the current category and block placement needed. This takes two to three minutes.

Block placement follows, with the patient comfortable on the treatment table. I stay in the room, monitoring the correction and adjusting as needed. After five to ten minutes, the blocks are removed and I assess what changed. In most cases, the pelvis has moved into a more balanced position, which then allows me to do specific work in the lumbar spine, mid-back, and cervical spine from a corrected foundation.

When indicated, cranial work is added at the end to address the other end of the dural tube. In SOT, the pelvis and the skull are always assessed as a unit.

Key Takeaways

• SOT blocks are wedge-shaped tools placed under the pelvis to use gravity and sustained gentle load — rather than force — to correct sacroiliac joint imbalance.
• The technique was developed by Dr. M.B. DeJarnette, who recognized that the pelvis and skull function as linked ends of the dural tube.
• The three SOT categories (I, II, III) describe increasing severity of sacropelvic involvement: basic SI imbalance, ligamentous sprain with dural tension, and disc involvement.
• Blocks work through tissue creep — allowing connective tissue to remodel under sustained low load, which holds better than brief forceful manipulation.
• Category II in particular benefits from the gentleness of blocks; forceful manipulation in a ligament-sprained SI joint tends to aggravate rather than correct.

Curious whether SOT block treatment is right for your back or hip pain? Call Pura Vida Chiropractic at (210) 685-1994 to schedule an evaluation with Dr. Dan Foss. We serve San Antonio in English and Spanish — hablamos español.