Loki - it's NOT tendonitis mate. Iv got the same problem. Its just an overuse injury that occurs during your teens (growing pains as doc said) and WILL disapear if you rest it. It can be healed with rest but sometimes takes months at a time. I'd say you need to stop what running you are doing (are you doing uphill/steps and downhill crosscountry?) and start swimming and building your legs up so that the impact may be absorbed better.
Also, as iv said before in another thread, get some new shoes/ insoles and get them properlly fitted by someone who knows what theya re talking about and take your time actually chosing them too!!
Knee supports dont seem to work on that problem and the pain keeps recurring. After about 3 weeks rest try running again (not straight into 80 miles a week, but gradually).
Id recommend these insoles as ever since iv used them, iv had no trouble with my knees.
REST A FEW WEEKS FIRST!!!
http://www.return2fitness.co.uk/Foot_Ca ... /soleultra
Bloody good i tell ya! And being a bit more optomistic than doc
