Dr. Jadali’s main assessment of foot pain in general:
EXCEPT IN RARE OCCASIONS, THE MAIN CAUSE OF THE FOOT PAIN IS NOT IN THE FOOT ITSELF…
Most of the pain in the foot and ankles usually arises from the higher above in hamstring and calves. Most of us have very tight muscles in the back of our legs that are called hamstrings (in the back of the thighs) and calves (Calf muscles are attaching the ankles to the knees in the back of the legs). The tightness of these muscles is the major contributor to the routine, non-traumatic foot pain.
The pain in the foot and particularly in the bottom of the foot most often is labeled as "plantar fasciitis" however mostly it is not the case. Most of the pain is coming instead from the tendons of your big toes that follow the same trajectories as the plantar fascia. This condition is called Flexor Hallicus Longus tendinopathy, in short, FHL tendinopathy. They usually get aggravated when wearing sandals that cause constant pushing of the big toe down to propel you forward.
Ultrasound examination of the foot can easily determine these conditions and tell them apart.