20/12/2025
🎄 Anatomy Advent - The Sacroiliac Joint 🎄
The sacroiliac joint connects the sacrum (the fused vertebrae at the base of the spine) to the ilium (part of the pelvis). Horses have two SI joints, one on each side.
Unlike many joints, the SI joint has very limited movement. Its primary role is stability, not flexibility.
⚙️ Function
The SI joint is a major force-transfer hub in the horse:
•Transfers power from the hind limbs to the spine
•Stabilizes the pelvis during locomotion
•Supports collection, engagement, jumping, and acceleration
•Helps absorb shock from the hindquarters
Because of this, it’s critically important for performance horses.
The SI joint is deeply supported by very strong ligaments, including:
•Dorsal sacroiliac ligaments
•Ventral sacroiliac ligaments
And is surrounded by large muscle groups (gluteals, longissimus, hamstrings).
This heavy support makes the joint very strong, but also hard to image and diagnose.
SI issues are common but often underdiagnosed. Problems may include ligament strain, inflammation, or joint dysfunction.
Typical signs of SI joint dysfunction:
-Poor or uneven hind-end engagement
-Difficulty collecting or maintaining impulsion
-Resistance to transitions
-Crookedness or drifting behind
-Bunny-hopping canter or disunited canter
-Reduced performance without obvious lameness
-Sensitivity to palpation over the croup or tuber sacrale.
Because the SI joint links the hindquarters to the spine, dysfunction here can:
-Mimic hock, stifle, or back pain
-Lead to compensatory injuries
-Severely limit performance if untreated
