The patella (note spelling) is the kneecap.
Protecton for your knee joint.
No Chihuahua's are not good pets for children. Because of their small size a chihuahua can be easily hurt or killed by a child. Chihuahua's also have very thin legs and often have problems with luxating pattela's. Chihuahua's also don't have the "love everyone" temperment" that a dog belonging to children should have. Chihuahua's bond closely with one individual...and they become very protective of that one individual. Most chihuahua's are very leary of small children, preferring to stay away from them.