Daisuke Matsuzaka visited a hospital in the Kanto region for a routine examination and to run tests on his right hand (he had difficulty gripping the ball during his last outing on May 14). No abnormalities were discovered.
[UPDATE 5/19 @ 3:30am]
To clarify: Matsuzaka was at the hospital for a routine examination. While specific tests were not performed on the hand, tests from the routine examination did not reveal any concerning abnormalities.
Source: ZakZak 5/18/2016