A joint endoprosthesis system has two prosthetic components to be affixed to two bones of a human joint. A sensor and electronic components are affixed to one of the prosthetic components so that a record can be maintained of the number of times the patient moves the prosthetic joint in a particular...http://www.google.ca/patents/US20050010299?utm_source=gb-gplus-sharePatent US20050010299 - In vivo joint implant cycle counter
