Winter sports can take a toll on your body if you're not properly warmed up. Make sure you take about 15- 20 minutes before your activity to get your muscles toasty! 

Skating: Do several lunges on each side allowing your back knee to drop all the way to the floor with each stride. Make sure you're keeping your supporting knee at greater than a 90 degree angle. 

Skiing: With your feet about shoulder width apart and your toes pointing straight forward, do several squats and make sure you wear layers.

Sledding: Bouncing over the snow can cause compression injuries so make sure you do some knee-to-shoulder stretches. 

You can learn more in this article from the ACA.