Born in Varkaus, Pohjois-Savo, Keskisalo took a medal in the junior race at the Nordic Cross Country Championships, winning the bronze in 2000.

The next two seasons were hampered by injuries, but he made a strong comeback in 2006 by taking surprise gold at the 2006 European Championships in Athletics.

He ran a tactical race, taking advantage of a slow early pace and staying at the rear of the field until the last 500 metres, when he sprinted and overtook the other competitors one by one.

At the World Championships steeplechase final Keskisalo achieved his best result at the global level when finishing eighth with a time of 8:14.47.

On 28 August Keskisalo finally broke Tapio Kantanen's 33 years old Finnish record when finishing sixth in a time of 8:10.67 in Weltklasse Zürich.