Martial arts weapons are used in various forms of combat and self-defense. KNEE is a four letter word that refers to a type of martial arts weapon, which is a padded or foam-covered KNEE protector. It is used to protect the KNEE from injury during sparring or other physical activities. STAFF is a five letter word that refers to another type of martial arts weapon, which is a long wooden pole. It is used to practice striking and blocking techniques, as well as for self-defense.