UAP in pets - Causes, diagnosis, treatment & recovery

Ununited Anconeal Process (UAP) is a developmental disorder of the elbow joint in which the anconeal process of the ulna fails to fuse properly. This causes pain, lameness, and joint instability. UAP is part of the elbow dysplasia complex and is most commonly seen in dogs, while it is extremely rare in cats.

In this article, we discuss the causes, symptoms, diagnosis, treatment, and recovery from UAP in pets.

What is UAP?

In UAP, the anconeal process - a piece of bone at the tip of the ulna that fits into the elbow joint - remains detached because it fails to fuse properly to the rest of the ulna during skeletal development. Normally, this piece of bone should fuse by around 20 weeks of age. When this does not happen, joint instability results, leading to pain, cartilage damage, and early-onset osteoarthritis.

Which animals are at risk?

UAP occurs mainly in medium to large dog breeds, particularly German Shepherds, Mastiffs, and Bloodhounds. The condition usually manifests between 4 and 12 months of age. In cats, UAP is extremely rare and usually secondary to trauma.

Symptoms in dogs and cats

In dogs:

• Noticeable lameness of the front leg
• Pain when bending and extending the elbow
• Reluctance to run or jump
• Reduced muscle mass in the affected leg

In cats:

• Extremely rare
• When present: subtle lameness or stiffness, usually after trauma

Diagnosis of UAP

Diagnosis is made through physical examination and imaging. X-rays can usually clearly show that the anconeal process has not fused. A CT scan can be useful for assessing any additional abnormalities. Arthroscopy can be used as a complementary tool to determine the severity of cartilage damage.

Treatment of UAP

Surgery is the standard treatment in dogs. Options include removing the loose fragment or performing an ulnar osteotomy, with or without screw fixation of the anconeal process, to reduce pressure on the elbow and promote healing. Conservative therapy (rest, pain relief) has little success and is rarely used.

In cats, conservative treatment is usually attempted first, given the extreme rarity of the condition and its often milder symptoms.

Recovery and aftercare

Surgery is followed by a rehabilitation period of 8 to 12 weeks. This includes controlled movement, physiotherapy, and hydrotherapy to rebuild muscle strength. The prognosis is variable: with early diagnosis and appropriate treatment, a good outcome can be achieved, but osteoarthritis often remains present in the long term. That said, this is the only elbow dysplasia condition that can be fully resolved with timely and correct intervention.

In cats, recovery is generally faster, but clear guidelines are lacking due to the rarity of the condition.

Want to know more?

Read more about our orthopedics and rehabilitation services. Our specialized veterinarians at Nesto have extensive experience with elbow conditions and are ready to provide advice.

Frequently asked questions (FAQ)

What exactly is UAP?

A developmental disorder in which the anconeal process remains detached, leading to pain and instability.

Is UAP more common in dogs or cats?

It occurs almost exclusively in dogs. In cats, it is extremely rare.

How is UAP diagnosed?

With X-rays, sometimes a CT scan, and occasionally arthroscopy.

What treatments are available?

Surgery is the preferred option in dogs: removal of the fragment or an ulnar osteotomy combined with screw fixation of the process.

How long does recovery take?

On average, 8 to 12 weeks. In cats, recovery is often faster.

What is the prognosis?

The prognosis depends on the severity of the condition and how promptly it is treated. With timely, successful treatment, the problem is resolved. With late diagnosis and treatment, osteoarthritis is unavoidable.