Hi Clair, first of all welcome to this amazing place, that is full of genuine people who are so supportive of each others hopes, goals & dreams.
Before I go on, I have to say that I would aleays defer to Eric with this.
In your post you did not say if you have read The Cool Impossible, if you hav'nt it's a must & so transformative.
It sounds to me as if your sore knees are a result of something changing. This could be a change of form, number of training days, terrain, shoes, number of rest days, introduction of strength training, changed training ,etc or a combination of these.
When we start sometimes our enthusam gets ahead of us and we try too much too quickly. We want to emulate all the amazing things we read about here but we have to start at the start being methodical, consistent ensuring to listen to our bodies.
Does the pain stop you from walking or does it happen only when you run or attempt to run & have you changed anything you can think of?
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