About a year ago I was cycling in Germany. It was an organised cyclingweekend, meant to keep in shape for the season to come. The weather was friendly, although a bit cold in the mornings, but temperatures were during the day comfortable enough to ride in cyclingshorts.
Our guide, having many years of cycling experience, told us that particarly these weatherconditions are the cause of many knee-problems racing cyclists suffer from. Because you think it's warm enough to ride in shorts, the knees are remaining too cold during the day which may cause rheumatic complaints in the years to come.
Keeping this in mind I actually bought a pair of knee-pieces, just to wear them while cycling in this time of the year when Spring just peeks around the corner.