Karlsson worked with a trainer before the Sharks' optional morning skate before their 4-2 loss to the Nashville Predators at SAP Center.
There is no timetable on a return for Karlsson, who has missed eight straight games.
"A good sign," Sharks coach Peter DeBoer said. "Out there, no setbacks, no pain. A first step, obviously. We're not close yet, but that's a good first step."
Karlsson, who did not speak to the media after his skate, told The Athletic on Feb. 8 that he'll 100 percent be ready to play in time for the start of the Stanley Cup Playoffs. The Sharks would have clinched a berth with a win against the Predators.