Sacroiliac Joint

Sacroiliac Joint

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The articulation between the canine vertebral column and the rest of the pelvis involves the sacrum and the ilium.

The canine sacroiliac joint is a combined fibrocartilaginous and synovial joint. The cartilage plate which unites the ilium to the sacrum, creates an incredibly firm union called the sacroiliac synchondrosis.

Regions of the pelvic limb (hind limb)
Regions of the pelvic limb (hind limb)

The canine sacroiliac joint is a very strong coupling between the canine vertebral column and the pelvic limb.

This supports the transmission of power from the pelvic limb musculature forwards along the spine, facilitating acceleration of motion in a forward direction.

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Clinical Tip: Forward sagittal plane motion is key to your choices of movement therapy techniques. It relates directly to canine biomechanics and gait; the dog's utilise this principal in their everyday canine activities.

The sacroiliac synchondrosis part of this important joint is craniodorsal to the synovial portion of the joint.

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Research in the 1980's showed the sacroiliac joint is capable of slight motion.

Sacroiliac Joint

The functional anatomy of the canine sacroiliac joint represents a very strong bond or coupling, that together with the surrounding ligaments, is tasked to transmit all the forces between the canine vertebral column and the pelvic limbs (hind limbs).

Canine Vertebral Formula: C7 - T13 - L7 - S3 (fused) - Cd 20-22

The sacroiliac joint is designed biomechanically for stability and therefore there is very little movement at this joint.

Sacrum

The canine sacrum is formed of 3 fused sacral vertebrae (S1, S2 and S3) to create a 4 sided shaped that has a concave ventral (pelvic) surface. S1 vertebral segment is larger than S2 and S3 combined.

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On the dorsal surface is;

The median sacral crest = the fused spinous processes of S1 - S3.

Two pairs of dorsal sacral foramina which houses sacral spinal nerves and other vessels.

The large cranial articular processes which articulate with L7.

The smaller caudal articular processes which articulate with the 1st caudal vertebra of the tail.

The left and right wings of the sacrum each have a large roughened auricular surface which articulates with the left and right ilium to form the left and right sacroiliac joints.

Ilium

The os coxae (hip bone) consists of 4 bones which fuse week 12 postnatal as the hip bone;

  1. Ilium (plural is ilia) is a flat bone with 2 surfaces and 3 borders.
  2. Ischium
  3. Pubis
  4. Acetabular (smallest)
Left wing of ilium, body of ilium and pelvis.
Left wing of ilium, body of ilium and pelvis.

The ilium is the largest of these 4 bones and the most cranially placed, being divided into the wing and a body.

Body of Ilium

The body of the ilium is a narrow, compressed shape and its expanded caudal end forms 2/5 of the acetabulum and fuses with the ischium, pubis and acetabular bones.

Wing of Ilium

Dorsal viewpoint of the pelvis complex.
Dorsal viewpoint of the pelvis complex.

The wing is a wide cranial part to the body.

It lies in the sagittal plane in the dog (totally different to the horse or cattle).

Its lateral aspect is concave cranially and its cranial boundary is the convex shaped iliac crest.

The lateral aspect (external) of the wing is called the gluteal surface.

The medial (internal) surface of the wing is known as the sacropelvic surface.

The sacropelvic surface of the wing of the ilium has a roughened C- shaped auricular surface which articulates with a similar surface on the wing of the sacrum, forming the sacroiliac joint.

Cranial and dorsal to the auricular surface is a smoother, nearly flat area for muscle attachment.

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In the dog (different to other species) the iliac tuberosity fills the space within the almost C-shaped auricular surface and extends cranial to it, providing attachment for ligaments that attach the ilium to the sacrum.

Ligaments of the sacroiliac joint include;

Ventral sacroiliac ligament is divided into 2 parts, the cranial and caudal parts. These consist of numerous short fibres that surround the joint to reinforce the stability and pass medially from the ilium to the sacrum.

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Dorsal sacroiliac ligament is larger than the ventral ligament and is divided into 2 parts, the short and long parts, which run medially between the ilium and sacrum.

Like the ventral ligaments, these reinforce the fibrocartilage of the sacroiliac joint and are bands of strong collagenous fibres. These run from the tuber sacrale and adjacent medial aspect of the ilium to the spines and lateral border of the sacrum.

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Sacrotuberous ligament is a cord like ligament with flattened ends. It runs between the ischiatic tuberosity and the caudolateral part of the sacrum plus the transverse process of the 1st caudal vertebra. This ligament is mainly covered by the Superficial Gluteal Muscle.

Locating the attachments of the left sacrotuberous ligament.
Locating the attachments of the left sacrotuberous ligament.
Location of the right sacrotuberous ligament from sacrum to the right Tuber ischii.
Location of the right sacrotuberous ligament from sacrum to the right Tuber ischii.

Clinical Perspective

Reviewing the bones involved in this complex joint between the sacrum and the ilium will assist in accurate assessment techniques.

Linking in-depth knowledge of the position and orientation of the joint's supporting structures will optimise the analysis accuracy and evaluation of each dogs functionality, related to problems or fitness challenges.

Palpating the Tuber Sacrale

Therapeutic palpation of the tuber sacrale.
Therapeutic palpation of the tuber sacrale.
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Palpating the Tuber Ischii

General palpation of the Tuber ischii. Explore using therapeutic palpation with a mindful approach of the structures.
General palpation of the Tuber ischii. Explore using therapeutic palpation with a mindful approach of the structures.
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Palpating the Lumbosacral junction

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Evaluating part of the hindquarter complex

Evaluating the distance from the left Tuber ischii to the greater trochanter and comparing left to right
Evaluating the distance from the left Tuber ischii to the greater trochanter and comparing left to right
By itself it's not sufficient but layer this into other therapeutic palpations of this complex provides you with a complete picture.
By itself it's not sufficient but layer this into other therapeutic palpations of this complex provides you with a complete picture.

OneShot Inside K9HS video 003

Empower your choices of the appropriate canine assessment and treatment techniques for each dog in your care, from your "Therapeutic Toolbox."

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Clinical Tip: Enjoy planning your CPD pathway to include developing your clinical skills relevant to the practice you wish to progress. A good idea is to use a Skills Log along with clinical reflection to guide your choices.

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