Dogs need their elbow joint to flex and extend through its full range of motion so they can walk, trot and run normally. Full range of motion in the elbow joint is particularly required for activities such as walking up stairs, stepping over obstacles, and jumping.

Anatomy of the dog’s elbow joint

The dog’s elbow joint is formed by three bones: humerus which forms the “arm” and the two bones of the forearm; radius and ulna.

The distal end (farthest end from the shoulder) of the humerus has two rounded ends (humeral condyle). The rounded outer end (when facing the dog) is the capitulum which articulates with the head of the radius. The larger inner end, the trochlear, articulates with the ulna to form a very stable hinge joint. The back of the humerus has a large, deep groove (olecranon fossa) which articulates with the ulna when the elbow is extended.

The radius, the shorter bone in the dog’s forearm, is the main weight bearing bone of the forearm. The proximal (top) end of the radius is an irregular oval shape that articulates with the capitulum and trochlea of the humerus.

The longer bone of the forearm, the ulna, serves mainly for muscle attachment. It articulates with the humerus and radius at the proximal end. The ulna articulates with the radius at the medial coronoid process and the lateral coronoid process. The medial (inside) coronoid process is larger than the lateral one. It extends into the medial surface of the elbow joint. Both coronoid processes articulate with the humerus and radius and increase the surface area of the elbow joint. Additionally, at the proximal end of the ulna is the site at which the powerful elbow extensor muscles of the joint attach.

Elbow disease and lameness in dogs

One of the main factors of elbow disease in dogs is thought to be radio-ulnar incongruence (RUI). The hypothesis of positive RUI is that the short radius shifts the joint load medially (inwards) which overloads the medial joint. The effect of joint overloading is cartilage damage or fragmenting the medial coronoid process.

Earlier canine studies have concluded that the severity of medial joint pathology corresponds with the amount of RUI. However, in 40% of canine elbow joints with medial coronoid disease there was no detectable RUI. It is therefore concluded that medial coronoid disease can develop in the absence of RUI.

Based on this conclusion, a recent canine study compared axial humero-ulnar rotation in normal and dysplastic canine elbow joints.

Study methodology

The dogs participating in the study were divided into two groups. The control group consisted of five dogs with no evidence of joint disease. The second group comprised six dogs diagnosed with medial coronoid disease.

Images of the movement in the dogs’ elbow joints were taken while the dogs walked on a treadmill.

Results

The study showed that in dogs with elbow disease at the beginning of the stance phase, there was significant outward rotation of the humeral condyle compared with the ulna. This level of rotation was not present in the control group. In dysplastic elbow joints the mean rotation was 5.3 degrees, compared with 2.9 degrees in the control group.

Additionally, in the diseased joints there was reduced joint contact between the humerus and ulna, presumably caused by the rotational instability in the joint. Reduced joint contact may contribute to cartilage damage or fragmenting of the coronoid processes.

Causes of elbow joint disease in dogs

It is commonly thought that medial coronoid disease in dogs develops from mechanically overloading the joint. This study shows axial humero-ulnar rotation may contribute to loading in the joint.

The cause for the motion in the joint may include the following:

• Alterations in muscle traction and ligament strength

It is hypothesized that soft tissue laxity may also play a role in elbow dysplasia. Release of lateral collateral ligaments places increased load on medial coronoid process

• Insufficient musculature

Theoretically, muscle weakness could contribute to joint instability. Exercises such as walking up an ascent, stair climbing or walking over low obstacles are effective in working the dog’s elbow through its full range of motion and therefore strength the supporting musculature.

Massage can also assist in building musculature surrounding the elbow joint and restoring normal joint range of motion.

For more information please see https://www.fullstride.com.au/blog/effect-of-massage-on-muscle-atrophy
http://www.fullstride.com.au/blog/passive-range-of-motion-exercises-for-dogs

Muscle strain in dogs with elbow disease

In 35% of dogs with elbow disease, they are lame in both front legs which has a profound effect on their gait. It is also likely to be a cause of pain and discomfort. As such the dog will attempt to shift their weight to avoid pain and in so doing overload the muscles in their back and neck. Massage treatments and heat therapy are beneficial in addressing compensatory muscle strain and pain.

For more information please see https://www.fullstride.com.au/blog/repetitive-strain-injury-in-dogs-and-how-to-treat-it
https://www.fullstride.com.au/blog/dog-s-leg-pointing-out

Full Stride provides remedial canine massage treatments in Brisbane, Australia. My goal is to relieve muscle strain, discomfort, and joint stiffness to restore your dog’s normal range of motion.

Until next time, enjoy your dogs.

Sources:

Evans, Howard and de Lahunta, Alexander (2013), Miller’s anatomy of the dog 4th edition, Elsevier Saunders, St Louis, Missouri, USA

Kainer, Robert A & McCracken, Thomas O (2003), Dog Anatomy: A Coloring Atlas, Telon New Media, Wyoming USA.

Rohwedder, T., Fischer, M., & Böttcher, P. (2018). In vivo axial humero-ulnar rotation in normal and dysplastic canine elbow joints. Tierärztliche Praxis K: Kleintiere/Heimtiere, 46(02), 83-89.