PS: Shih Tzu tend to have bowed legs.
https://www.yourpurebredpuppy.com/faq/shihtzu.html (excerpt below)
A Shih Tzu can be a great little dog, but the reality is that his physical build is neither natural or healthy. The Shih Tzu, in fact, is afflicted with two skeletal deformities: chondrodysplasia and brachycephalic syndrome.
Dogs were never intended to have a long back and short legs, especially if the legs are bowed (like Queen Anne furniture legs). This build is caused by a genetic skeletal deformity called chondrodysplasia, which translates roughly to “faulty cartilage.”
When a puppy is developing in the womb, his skeleton is first formed in cartilage as a sort of model. As he continues to develop, the cartilage is supposed to be replaced by bone. But if, because of certain inherited genes, the cartilage doesn’t transform properly into normal bone, the puppy will be born with incorrect proportions of cartilage and bone.
The result is a large head and chest, short, thick, bowed front legs, and a longish back with calcified disks that lack elasticity and cushioning powers and are predisposed to coming loose and protruding into the spinal canal (intervertebral disk disease). Chondrodysplastic dogs are also more susceptible to joint problems, and later in life, arthritis.
