I've worn birkenstocks for 20+ years. It's pretty much all I wear. I tend to have semi-flat feet and need the arch support for comfort. The last month, I've been experiencing pain in my right foot only. It hurts worse upon weight bearing and walking after resting. It does not seem to get better when I'm on my feet longer. My arch has a pain very deep inside the foot. The pain on the outside of my foot is now radiating up the back of my leg (wrapping around to the achilles tendon. The tendon feels tight. I did not injure my foot in any way. I'm not a runner, but I do ride an exercise bike. The PAC I went to see did not know what it could be. He said it probably wasn't plantar fascitis (I don't think it is either). Do you have any thoughts as to what it could be? I'm thinking tendonitis...I hate taking ibuprofen, but 600 mg once daily does seem to help take the edge off. Oh, if I torque my foot in a way that my arch is almost touching the floor (turning my foot outward) the pain shoots from my arch, across the bottom of my foot to the outside of my foot, just beneath my ankle bone. The pain is also starting to go up the back of my calf and my achilles tendon feels tight. Thank you for your reply.