It's a funny thing about knee injuries. They're never what they appear to be.

Grady Sizemore injured his left knee sliding into a base over 10 months ago. It didn't seem serious. Just a bruised knee, but he still can't run the bases or play center field as the Indians open spring training Thursday with their first official workout for pitchers and catchers.

Then there's catcher Carlos Santana. On Aug. 2, at Fenway Park, Ryan Kalish slid into Santana's left knee at the plate. Santana was waiting on a throw from right fielder Shin-Soo Choo as Kalish tried to score from second on a single.

Catching is a difficult job. Taking a throw from right field with a runner trying to score from second ranks high on a catcher's list of hard tasks. It's hard because the catcher can't see the runner coming as he waits for the ball.

Santana caught Choo's throw and turned to block the plate by putting his left leg in front of it. Kalish almost jumped into Santana's leg with his own legs, knocking him head over heels. The force of the collision was so great that Santana was literally knocked out of one of his shoes.

Somehow Santana held the ball. Kalish was out, but so was he. At worst, the injury seemed to be career-ending, at best career-altering.

Surgery followed both injuries. Sizemore underwent microfracture surgery on June 4. Santana had surgery on Aug. 6 to repair a torn lateral collateral ligament on the outside part of his knee. Sizemore, who looked like he hardly mussed his hair, sustained the most damage. Santana, literally run over, is scheduled to go through Thursday's workout without restrictions.