Radius curvus syndrome in dogs: causes, signs and treatment

With radius curvus syndrome in dogs, the two bones of the forearm, the ulna and the radius, don’t grow evenly. Usually the growth plate of the ulna stops growing too early while the radius keeps growing. Because both bones are connected, the radius bends and the paw turns outwards. This happens during growth. So if you notice a crooked foreleg in a puppy or young dog, have it checked by the vet early, while there is still growth left.

What is radius curvus syndrome in dogs?

The forearm has two bones lying side by side: the ulna and the radius. Both grow at growth plates near the joints. If the growth plate at the lower end of the ulna closes too early, the ulna stays too short. The radius keeps growing but is held back by the ulna and curves. That is where the names come from: “short ulna” for the ulna that is too short and “carpal valgus” for the paw that bends outwards. The elbow can also be thrown off balance, because the joint surfaces no longer fit together precisely.

How does it develop?

• Growth plate injury: A crush injury, for example from a fall or accident, can stop the ulna from growing, even if the bone itself is not visibly injured.
• Developmental disorders: Sometimes ossification at the growth plate simply doesn’t proceed normally.
• Predisposition: Dogs of short-legged breeds such as Dachshunds or Basset Hounds carry an inherited peculiarity in bone growth. Similar deformities occur in them, often with a more complicated course.

How do you recognise radius curvus syndrome?

• Crooked forearm: One or both forelegs look bent.
• Paw turned out: The paw points clearly outwards.
• Difference: The forelegs look different on the left and right or differ in length.
• Lameness: Your dog limps, favours a foreleg or doesn’t want to walk after playing.

Why timing is so important

Without treatment, the deformity usually keeps progressing as long as the dog is growing. In young dogs, however, there is still growth left that can be used. That is why it pays not to wait with a conspicuous foreleg, but to have it checked early.

How does the vet diagnose it?

The vet examines your dog’s gait and joints and takes X-rays of both forelegs. This makes it possible to compare bone length, curvature and the position of the elbow and wrist. Sometimes a CT follows to measure the deformity precisely and plan a procedure.

How is it treated?

• Partial removal of the ulna: In young dogs, the vet often removes a short piece of the ulna so that it no longer holds the radius back. In a study of 23 young dogs aged 4 to 11 months, lameness usually improved afterwards and the deformity did not progress further. However, existing angles were not corrected by this.
• Straightening the radius: If the deformity is already pronounced, the vet can cut the radius, straighten it and stabilise it.
• Aftercare: After a procedure, your dog needs bandages, rest and check-ups. In the study, complications occurred in just under a third, mostly minor bandage problems.

How to support your dog in everyday life

• Exercise as planned: Stick to the vet’s guidance on how much and what kind of exercise is allowed.
• Non-slip floors: Rugs or mats on smooth floors give grip.
• Avoid jumping: Avoid jumps off the sofa or out of the car for as long as the vet recommends.
• Keep check-ups: Have the leg checked regularly during growth so that any change is noticed early.

Frequently asked questions

Source

• Christopher S.: Short term outcomes and complications of distal ulnar ostectomy in 23 juvenile dogs with carpal valgus secondary to discordant radial-ulnar physeal growth, Frontiers in Veterinary Science 2022.

A crooked foreleg in a young dog is not a cosmetic flaw to wait out. The earlier the vet takes a look, the more options there are.