Any advice for ankle and knee pain due to flat feet?

Flat feet can cause discomfort in feet, but with the correct approach, the issue can be solved. Your previous insoles might not be suitable and probably need custom made insoles to deal with it. You can opt for custom made insoles by UpStep. Their experts would examine your issue with flat feet to deliver you the best possible custom insoles.

Pain can be debilitating and chronic if not dealt with correctly. Orthotics can provide your feet with the support and weight distribution qualities they need to have optimal biomechanics while walking or running. Orthotics will prevent the inward roll of the ankles, aligning the knees and hips while walking or runnings. This should prevent pain arising from your ankles to your hips during activity. 

Orthotics that are older may not provide enough support to the foot due to the materials losing their integrity with age. This may aggravate your symptoms of pain further. Using double sided adhesive tape on the underside of your orthotics may stop them from moving in your shoe. Custom orthotics may be your best bet in finding the best option for managing the pain you may be experiencing in your feet.