To explain what dirty kata is, let us explain how kata is usually clean.  As kata is the art form/performance side of karate there is a strong emphasis on precision, balance, control, poise, dramatic timing and expression. This performance aspect of kata has been further characterised by the tournament/competition kata which prizes it. As a result, this performance art form in many styles has overtaken the true purpose of kata which was to practice self-defence.  So rather than being a way of practicing self-defence techniques and movements, tournament kata in some cases has become a performance and closer to a dance than self-defence. This is not to say that the self-defence is not still “hidden” in the moves, and practitioners are still practicing principles of movement.

Dirty kata ignores performance aspects and focuses completely on the application or bunkai. Performers of dirty kata do not care for the exact angles of stances or other finicky details (unless it dramatically affects the effectiveness of the technique), nor do they care any of the dramatic performance aspects kata, they are only concerned with its practical application.  As a result dirty kata can look messy, even undisciplined, slapdash or unrefined. This is not to say it lacks expression, though, dirty kata is very expressive but the focus of this expression is not on poise and control rather, aggressively defending yourself, displaying high levels of “kime” (intent).

So which is best dirty or clean kata?

Dirty kata takes karate back to its roots of actually being self-defence-based martial art.  Practitioners are forced to explore the bunkai (applications) and oyo (principles or concepts) that drive moves and sequences. This makes the study of kata much more practical and the skills you practice more readily applicable in self-defence and sparring as opposed to being abstract and not obviously transferable as is often the case in clean kata. One of the problems with dirty kata is that the bunkai sometimes have multiple applications and some moves are simply impractical without massive modification to the technique or pattern of the kata.

Practicing clean kata develops a sense of self-mastery. The exacting movements demand that you master control of your body, this is a foundational principle of many martial arts and one of the key benefits of training in karate. It teaches patience and self-control. The danger with clean kata is that students tend to practice it with little thought of the purpose and application of the techniques they are learning. This is obviously a cause for great concern as their focus has drifted away from the primary point of doing kata in the first place. Essentially clean kata prizes from of function.

With these considerations in mind, it is clear neither is best, but both practices teach different sides of the same coin.  One to the exclusion or detriment of the other always leads to an incomplete study of kata.  A good student should aim to understand both and bring them both into balance in their kata. This is not to say they should do half and half all the time. They should focus on each of the two at different points in their karate journey to make sure they understand and value the true nature of both.

Is one more important than the other? The answer has to be “dirty”, prioritising function over form is only common sense, function is the original purpose of kata.