Knee Collapses when Running

Question
I am a 60 year old male vegetarian who has been running for about 35 injury free years. For the last 10 years I have running on a treadmill for 4-5 miles per day, 6 to 7 days a week. Recently when running my right knee collapsed. I grabbed the  treadmill handles and continued in stride, then slowed down, got off the treadmill and did some stretching exercises before continuing to run again and did not experience any problems. Since I did not feel any knee pain I ran the next day and did not experience any problems. I always do a 5 minute warm-up walk before running and stretching and yoga after running.I am 5'7" and weigh 120 lbs. Do you have any suggestions on what caused this and how to prevent in the future.  

Answer
Hi Allan
I think there could be a little bit of a tracking situation which can happen quite easily as your knee glides up and down in the grove.The one course of action that i use for many clients who have knee situations is a up right stationary bike since it does a fantastic job on the tracking and alignment issues that surface from time to time and also it helps strengthen quads which is very important in supporting proper tracking.That is very likely what could of happened,but i don't really think it is serious,but it is your body talking to you to address the situation like your doing.If you have other question on it just give a holler Allan.Congratulations on your great wonderful record.

All the best

John