I wonder how frequently a lateral epicondylitis has an anatomical cause. When searching for the information, I couldn't find any specific numbers, and the information I read was ranging from "there is often an anatomical problem" to "[it is a ] rare cause". Obviously it may depend on the age of the individual, and other factors. If so, assume a 25 year-old individual (though I am curious about other ages as well).
Below are some references, sorted by how frequent the anatomical cause is, descending order.
Anatomical Problem: Tendons in the human body are like a bundle of rubber bands. These rubber bands function best when they are all parallel to each other. Most often, tendonitis affects the alignment of the fibers, or band-like structures, of the tendon. Instead of presenting with fibers aligned parallel, many of the fibers are crossed. The crossing of the fibrous structures of the tendon causes the muscle and tendon to operate at a disadvantage, which causes the body to experience pain and inflammation. Therefore, there is often an anatomical problem with the tendon underlying tendonitis.
Often, there is an anatomical cause for tendon disorders - some people just have a problem with the way they are built or the way they move...and that needs to be addressed
Sometimes, there is an anatomical cause for tendonitis. If the tendon does not have a smooth path to glide along, it will be more likely to become irritated and inflamed. In these unusual situations, surgical treatment may be necessary to realign the tendon.
Anatomical cause of tendonitis: Anatomy is a rare cause of tendonitis. If the tendon does not have a smooth surface area in which to work against it will often become inflamed and irritated quite easily. In these situations surgery is often required to rectify the problem.