When I was in Veterinary school 31 years ago, they taught us in anatomy 101 that the sacroiliac joint was fused and of little importance in locomotion. Fast forward to three years ago when I was training in spinal manipulation at the Integrative Veterinary Medicine Institute and they discussed how important the sacroiliac joint is in locomotion, and its role in pain and gait abnormalities. Needless to say, I was amazed at how traditional medicine differs from the osteopathic perspective.
The sacroiliac joint is composed of the Sacrum, which in dogs and cats is usually 3 fused vertebrae that have 2 sets of large foramina. The Sacrum is like an inverted pyramid in which the wider base articulates with the last lumbar vertebrae (#7) and on either side with two flat bones called the Ilium: that is the sweet sacroiliac joint! The ilium is fused to other bones that make up the pelvis. Therefore, the Ilium interaction with the Sacrum could definitely affect the motion in the hip joints.
So, how can this joint get in trouble? Well, there can be three different chiropractic adjustments based on the displacement of the Ilium and in spinal manipulation of animals we still use those human terms to describe displacement in the sacroilliac joint. The wing of the Ilium could be displaced dorsally (aka posterior) and towards the tail (caudally aka inferior) resulting in that side looking higher than normal (called PI) and causing the surrounding muscles to be very tense. The hip is resistant to be extended and the pet is uncomfortable. In that case a quick manipulation in the opposite direction or cranioventrally will bring immediate relief and will reset the affected muscles. The Ilium can also be stuck ventrally (anterior) and towards the head (superior) which will cause difficulty flexing the hip and cause the muscles to be tense as well ( this is called AS).When we evaluate the pets, we observe them from behind, looking to see if there is a higher or lower side, then test the range of motion to determine if there is a restriction. The third displacement is really the apex or end of the sacrum being displaced to either side and causing friction with the ilium.
I have personally experienced a left PI when I moved quickly to help an acupuncture patient and the awkward angle pushed my sacroiliac joint out of normal position. It was painful and I could barely walk. I used cold laser and acupuncture and it made the pain decrease by 50% but it was only when I went to my chiropractor, Dr. Briggs, and had a simple adjustment that my pain completely disappeared. That experience was invaluable because I now know the importance of diagnosing and treating the sacroiliac joint in our senior pets. The range of motion in your senior dogs and cats might be limited by osteoarthritis as well as the sacroiliac joint displacement. Distinguishing between those issues is a must if we want a quick resolution of pain and return to function.