Injuries have really played a role in not only the Finals, but the postseason for both BOS and LA. Celtics Pierce, Perkins, and Rondo have been slowed by various problems.
For LA, Ariza missed most of the playoffs and and their starting center -- Andrew Bynum -- has been out since mid-January. [Again, what a difference he'd have made in this series...] Mihm just returned from injuries and has only played in a single game this series.
It's not football, but NBA players put an incredible amount of stress on their bodies over the course of an 82-game season. And for the Lakers and Celtics, these guys have been playing for nine months. Over time, even the best-conditioned players wear down. If the average active Baby Boomer is having trouble with wear-and-tear injuries, imagine what playing pro basketball can do to your body.
Teams have different philosophies and approaches to medical problems and injuries. Moreover, players take different approaches to their own injuries and what's reported to the media through the training staff.
I've had players who didn't want anyone knowing when they had small injuries that wouldn't impact their minutes. Others wanted every knick and knack -- even head colds -- reported.