Thank you for your questions. It comes at an appropriate time, when more and more people are taking up running as a hobby, recreational or amateur sport.
Flat feet can generally be divided into 2 types. The more common juvenile/ adolescent painless flexible flat feet - which sounds like what you have.
If you run and walk, and have flat feet but it is painless, a lot of times, we will just observe and watch.
We may need to examine the feet properly, do some investigations to make sure there is no other underlying pathology, and reassure you. Some people may benefit from insoles or better footwear. They do not usually lead to increased risk of other injuries to the ankles or knees.
The less common cause of flat feet are what we call adult acquired flat foot disorder (AAFD). This is usually painful, even from normal walking. It may be associated with a flat foot deformity or even other deformities to the foot. AAFD would be more important to manage and treat properly, as it can lead to other potential problems in the ankles, and subsequently the knees.
I hope I have managed to answer your queries. If your feet are symptomatic, then it would be prudent for you to consult an orthopaedic surgeon, to identify the cause of the flat feet and help manage them properly. Otherwise, happy running!!!
Best regards
