Hiking on icy tracks all winter has been so much safer using trekking poles.   They add stability, take pressure off the knees, and are great for testing the snowpack.  

Many people use two, but I prefer to have one hand free for a map, camera, or GPS.   My pole is always in the truck and goes with me on every hike.    The other half of the pair sits at home waiting to take its turn.  

One of the best articles on trekking poles is found here.