Elbow dysplasia II.: Ununited anconeal process (UAP) in dogs

The elbow joint is one of the most complex and weight-bearing articulations in a dog’s body. Any structural abnormality in its development can result in serious pain, and progressive osteoarthritis (OA). One of the most severe forms of elbow dysplasia is the Ununited Anconeal Process (UAP), a developmental orthopedic disease that leads to instability in the elbow and severe degenerative changes over time.

Early diagnosis and treatment are crucial to preserve the joint’s function and prevent permanent cartilage damage. But how can dog owners detect elbow problems? And what are the best treatment and rehabilitation options for affected dogs? Let’s dive into the anatomy, causes, symptoms, and solutions for UAP.

Anatomy of the canine elbow joint & the anconeal process

The elbow joint is formed by three primary bones:

1. Humerus – The upper arm bone, which has the humeral condyles that articulate with the ulna and radius.

2. Radius – The main weight-bearing bone in the forelimb.

3. Ulna – The stabilizing bone of the forearm that contains critical landmarks such as:

• Olecranon process: The bony prominence at the back of the elbow (where the triceps attach).

• Trochlear notch: The curved surface that articulates with the humerus.

• Anconeal process: A small projection at the top of the ulna that helps stabilize the elbow joint by interlocking into the humeral fossa when the limb is extended.

• Medial and lateral coronoid processes: Contribute to joint stability but are commonly affected by other elbow dysplasia conditions such as FCP (Fragmented Coronoid Process).

What is an Ununited Anconeal Process (UAP)?

In normal puppies, the anconeal process develops as a separate center of ossification between 8-12 weeks of age. By 16-24 weeks, it should completely fuse with the rest of the ulna to form a stable elbow joint. However, in dogs with UAP, this fusion does not occur, leaving the anconeal process loose and detached inside the joint. This results in joint instability, abnormal load distribution, and pain. Over time, this leads to progressive osteoarthritis, joint degeneration, and loss of mobility.

What Causes UAP?

Several factors contribute to the development of UAP:

- Genetic predisposition – Strongly hereditary in certain large and giant breeds.
- Elbow incongruence – If the ulna is too short (ulnar hypoplasia), excessive pressure on the anconeal process prevents it from fusing properly.
- Rapid growth & nutrition – Imbalanced calcium-phosphorus levels or excessive calorie intake may contribute to improper bone development.
- Trauma or excessive exercise in puppyhood – Repetitive high-impact activities (jumping, rough play) may stress the joint during its critical development period.

Breeds Predisposed to UAP

Certain breeds are at higher risk due to genetic factors, including:

• German Shepherds (most commonly affected)

• Rottweilers

• Bernese Mountain Dogs

• Newfoundlands

• Mastiffs & Great Danes

• Saint Bernards

• Labrador Retrievers 

• Golden Retrievers

How Can Owners Detect an Elbow Problem?

Dog owners should pay close attention to early warning signs of elbow discomfort, specially if you have a Puppy! UAP can show clinical signs at 4-8 months! You can never lower the attention, watch out and I recommend you to make videos every second week of your puppy in motion: walking, trotting from both sides, from the front and end. Let's get back to the symptoms: 

✔️ Intermittent or persistent lameness (worsens with activity)
✔️ Pain & stiffness in the front legs after resting
✔️ Reluctance to extend the elbow or bear weight on the limb
✔️ Elbows held outward ("paddling" gait) to relieve pressure
✔️ Pain when touching or flexing the joint
✔️ Swelling at the elbow
✔️ Behavioral changes (irritability, avoidance of activity, decreased enthusiasm for walks)

If left untreated, the loose anconeal process continues to cause chronic irritation, leading to severe arthritis, cartilage wear, and permanent joint damage.

Diagnosis of UAP

Accurate diagnosis requires imaging techniques such as:

1. X-rays (radiographs): The anconeal process appears detached or floating from the ulna.
2. CT scan: Provides a detailed view of joint incongruence and secondary arthritis.

Treatment options for UAP

Surgical Treatment (The best for young Dogs - don't negleckt their pain, this is the only solution that can give good outcomes)

Anconeal Process Removal: If the detached fragment is causing pain, surgical removal helps eliminate irritation.
Proximal Ulnar Osteotomy (PUO): If elbow incongruence is present, this procedure allows the ulna to reposition, reducing joint stress and improving weight distribution.
Internal Fixation with a Screw: In younger dogs (before 6 months), a screw may be placed to help fuse the anconeal process to the ulna.

Rehabilitation & Conservative Management & Physiotherapy

For older dogs or those unable to undergo surgery, physiotherapy helps manage pain, improve joint function, and slow arthritis progression.

1. Manual Therapy & Myofascial Release – Releases tension in overcompensating muscles.
2. Targeted Strengthening – Exercises focus on triceps brachii, biceps brachii, pronator, supinator and other stabilizing muscles.
3. Low-Impact Exercise – Controlled leash walks & cavaletti work improve joint mobility.
4. Laser Therapy & Shockwave Therapy – Reduces inflammation and pain.
5. Joint Supplements – Here you can find more detailed needed joint supplements: https://happydogtherapy.es/blog/elbow-dysplasia-in-dogs-1

Scientific References & Book Recommendations

📖 Books:

• "Canine Rehabilitation and Physical Therapy" – Darryl L. Millis & David Levine

• "Advances in Canine Orthopedics" – Martin Fischer

📄 Studies:

• Meyer-Lindenberg et al. (2020). "Prevalence and Diagnosis of UAP in Large Breeds." Veterinary Surgery Journal.

• Fox S. M., Burbidge H. M., Bray J. C., Guerin S. R., (1996): "Ununited anconeal process: Lag screw fixation" J. Am. Anim. Hosp. Assoc.

• Wind A.P. (1986). "Elbow Dysplasia in Dogs: Pathogenesis & Genetic Correlation." Journal of Veterinary Orthopedics.

• Lavrijsen IC et al. (2014). "Elbow Dysplasia and Genetic Heritability in Dogs." Veterinary Journal.

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