A telescopic shaft comprises an inner shaft, an outer shaft, which defines a tube and surrounds a part of the inner shaft and which is movable in the axial direction in relation to the inner shaft, two ball tracks arranged in the inner shaft, and balls arranged in the ball tracks. Each one of the ball tracks comprises an outer ball track portion, which is partially open so that the balls are arranged to roll between the outer ball track portion and the inside of the outer shaft. The telescopic shaft comprises at least one movable ball track member and a spring member which is arranged to press the movable ball track member and the balls arranged in the ball track member against the inside of the outer shaft in order to pretension the telescopic shaft.