Chihuahuas are toy dogs that are low to the ground. The average Chihuahua weighs 6 lbs. Being a small dog in a big world requires the Chihuahua to constantly look up at everything -- a motion that can lead to hypermobility in the neck. Hypermobility is an over-extension or over-flexibility of any joint.
Hypermobility of a Chihuahua's neck can lead to other neck- or back-related disorders, generally involving the connective tissue, joints and muscles. The hypermobility and excessive extension of the neck has the potential to become painful to the dog, due to the constant stress at the base of the neck and the shoulders.
A Chihuahua that appears to have stiffness in the neck or difficulty moving it up and down or back and forth may be experiencing pain from the hypermobility. Dr. Bari Spielman says to also look out for a change in your dog's posture, such as arching of your dog's back, a reluctance to move the head, yelps of pain when the neck is moved or touched or the appearance of difficulty walking.
To determine the cause of your Chihuahua's neck pain -- or to determine if the pain is coming from the neck or elsewhere -- a veterinarian must take an X-ray. The vet may also do spinal radiographs and CT scans to determine the cause of the neck pain.
You might be able to prevent hypermobility of your Chihuahua's neck by noticing when your Chihuahua is straining its neck to look up, and placing it on a more level plane. Keeping your Chihuahua perched eliminates the need for the neck to constantly stretch up. You can also play on the floor with your Chihuahua and bring its attention toward the floor. For instance, rather than holding a treat up high in the air for your dog to look at, bring the treat to eye level.