Firstly, the most obvious symbol of knowledge is the grading system and rewarding of coloured belts (or Dans if one is a black belt) upon successfully completing a grading. The ingredients of knowledge are TIME, COMPREHENSION and APPLICATION (TRAINING/PRACTISE). Like any form of knowledge one must commit the time to learn the subject, however, you can only learn something when you comprehend what is being taught and finally you must apply that knowledge or understanding to years of training or practice. Once those conditions are met, I believe one is on the path to true knowledge of an art. I think the final step is when one becomes the TEACHER (not that one ever stops learning).

To me knowledge in the physical arts is different to cerebral knowledge; it is a kinesthetic knowledge which comes from practice and experience. It is about being able to respond appropriately to a stimulus, being aware of your center of gravity, being able to control your breathing, being able to relax and tense your muscles to facilitate effective striking, being able to use the hips and the shoulders, having an awareness of range, stance and posture, being able to perfectly time your techniques, knowing how to absorb a fall or a strike.

I'm not sure if martial practise is an art form. Martial arts in the 17th century in Japan were actually referred to as Martial science. It wasn't until the rise of the gun and cheap mass production that the 10 year long martial warriors became redundant and had to find other meaning and purpose for their skills (and the change of the word science to art). Thus Martial arts and the training methods change to suit the need of the people who practise. However unlike dance, music and other art forms your creativity is hampered by the fact that a wrong action leads to consequences (being punched in the face). There is a performance and a skill to demonstration for teaching purposes but every teacher understands that line. Anyway to answer the question (even if I don't think martial arts counts as an art) Knowledge in physical arts is an internal (or unconscious) understand of physical movement and it's function (or consequence) to an external environment. Jory