Dustin Johnson pulls out of Masters

Dustin Johnson has withdrawn from the upcoming Masters with an unspecified injury.

Reports have suggested that the world number 12 has suffered a setback in his recovery from a knee complaint.

The American underwent surgery on the injury last November in an attempt to correct the problem.

He last competed at the WGC-Cadillac Championship in Doral last month.

Johnson has previously competed in three Masters events.