Clicking sound in my left knee while I go upstairs (no pain though)

Question
QUESTION: Hi Nick!
I'm 22 and I've been running casually for a few years. Just until a few months ago I've been running more often to train for marathons in the summer. The other day I was finishing up a run and accelerated down a mild hill. The next day I notice a clicking sound coming from my left knee as I went up stairs. There isn't any pain yet but I'm worried about any permanent damage I might've done to my knee to cause that sound.
Is there anyway to get rid of this clicking sound from my knee? Should I focus on strengthening my knee and the muscles surrounding it? I also hear that biking helps stregthening the knee or will that do more damage?
do also have any training tips for training for marathons so I don't cause anymore damage to the rest of my body.
I really look forward to your response! Thank you!!

ANSWER: Joleen, First, I'm terribly sorry it took me a few days to respond. I've had family in town and haven't been on top of other things!  

I'm glad to hear there isn't any pain!  Without pain I wouldn't be too worried, but I would try resting for a few days to see if the clicking goes away.  I would also try to doing a 1-leg- sit-to-stand exercise (I'll post the video at the bottom of this).  If it is easier on your right then your left leg then 3 sets of 6 on your right leg and 3 sets of 2 on your left leg for 4 days in a row.  On the 5th day do 3 sets of 6 on both legs and see if it's the same difficulty on both legs.  If it's not easier on your right then don't do this exercise.  (This may seem strange to you, but I did not mistake which leg I told you to work.  This will likely help a lot.)  

Biking can't hurt, but there's no special benefit to your knee from biking.  Biking works your quads more than your hamstrings and both stabilize your knee.  Running works both quads and hamstrings.  

Finally, I do have training tips.  I like running on different slopes.  That is excellent. Also,   at least one day a week do intervals of about 60 seconds hard running and 180 seconds of a very light jog/walk. When I say hard I mean you can't go 65 seconds at that pace. You can only do 60 seconds because it's so hard.  Do this 6-10 times depending on your level of conditioning.  (These numbers can be changed.  You want a 2.5- 4 rest to work ratio when doing intervals of this type.)  This will improve increase your lactic acid threshold and improve your body's ability to recover and to have more energy while running long distances.  

Good luck and please let me know if you have any further questions or more information that can help me help you!

http://www.youtube.com/watch?v=MEtrqCu8Ne8

---------- FOLLOW-UP ----------

QUESTION: Thanks for the advice Nick! I've given my knee rest for 6 days and still no improvement :(. But I started the leg excercise you sent me so I will give you an update in a few days! Wish me luck!! And if you have anymore advice please let me know!
Thanks again for your help!! You've been very knowledgable :)

Answer
You're very welcome Joleen!  My next advice is to experiment with different foot strikes.  This may not get rid of the clicking, but it's nice to have different options if it does start causing you pain.  Further, the different foot strikes will strengthen your feet and ankles which often improves knee problems.  We have to remember that the knee (similar to the elbow) is the connector between foot and hip.  If we have correct alignment in the foot and hip then our knee can't help, but be in the right place.  Below are two links to videos that will be helpful.  They often illustrate different foot strikes barefoot, but the same foot strike can easily be done with shoes. It is better illustrated without shoes though.  I look forward to hearing from you in a few days!

http://barefootrunning.fas.harvard.edu/4BiomechanicsofFootStrike.html

http://www.youtube.com/watch?v=7jrnj-7YKZE