Could be any number of factors really. Imbalances in leg muscles, and hip flexors. Shoes. Upping the mileage too sharply. Lacking proper stretching. Proper shoes.

What kind of shoes are you currently using? If you are serious about running it's worthwhile going to a reputable store and getting a gait analysis done and finding the proper shoe, it makes a world of a difference. Whether you supinate, pronate, or are a neutral fit - there will be a different shoe for you. Don't fall into the trap of minimalist shoes, because they definitely aren't suitable for everyone, especially someone that needs a lot of support due to overpronation or collapsing arches.

I can help you out with some shoe advice if you tell me what gait you have.

Also, elevate and ice after your run and wear compression sleeves too. However, running in compression sleeves isn't for everyone - I personally can't.

This post was edited by Jordo on Feb 18 2015 11:08pm