If a cats exercise is sporadic it would be advantageous for them to stimulate bone growth while at rest. Therefore, having an internal vibrational therapeutic system to stimulate healing would be advantageous, and would also reduce edema and provide a measure of pain relief during the healing process. Unfortunately there is no easy way to test this hypothesis. Strangely, after speaking with several of the foremost specialists on animal bones, it was discovered that there has apparently never been a study on any small cat bones, not serval, caracal, puma, ocelot, or domestic. Only cheetah and tiger bones have been studied, and tigers do not purr.
Cheetahs do purr, but they are one of the most unique and specialized forms of the felid family.
The study would have to be entirely non-invasive. The dilemma is that most all cats purr, even under duress. A naturally occurring, non-purring cat is very rare, and this effect is usually associated with a physical problem. Cats that have physical problems related to purring cannot be admitted to the study because of the possible variables presented by the physical disability. Therefore, any research would have to be non-invasive and observation based.