How many total articulating joints comprise the lumbosacral motion unit in the horse?

How many total articulating joints comprise the lumbosacral motion unit in the horse?

• A. 3
• B. 5
• C. 4
• D. 6

Answer: (B)

The lumbosacral motion unit is the functional block formed by the last lumbar segment and the first sacral segment, including all articulations that directly contribute to motion there. In the horse, this unit comprises four facet joints—two between the upper and lower lumbar interfaces (one on each side) and two between the lumbar and sacral interfaces (one on each side)—plus the intervertebral disc between the last lumbar and the sacrum. That adds up to five articulating joints in the lumbosacral motion unit. Sacroiliac joints are pelvic joints and are not counted as part of this spinal motion unit.

The lumbosacral motion unit is the functional block formed by the last lumbar segment and the first sacral segment, including all articulations that directly contribute to motion there. In the horse, this unit comprises four facet joints—two between the upper and lower lumbar interfaces (one on each side) and two between the lumbar and sacral interfaces (one on each side)—plus the intervertebral disc between the last lumbar and the sacrum. That adds up to five articulating joints in the lumbosacral motion unit. Sacroiliac joints are pelvic joints and are not counted as part of this spinal motion unit.