Question
I was dx with plantar fasciitis about 4 years ago.  I tried pt, taping, stretching, night splints, cortisone shots, custom orthotics with good shoes, walking boot, ESWT to no avail. I had two rounds of cryosurgery about a year ago which did help reduce symptoms greatly.  Despite feeling a lot better, a new ultrasound performed about 7 months ago showed that the fascia is still very thick (7.5).  I was born with prominent accessory navicular bones on both feet.  About 7 months ago, the navicular on my left foot became quite tender to the touch which prevented me from wearing my orthotics and most shoes. I was also diagnosed with flexible flat foot. The posterior tibial tendon was quite inflamed also. I went through PT and immobilization in a walking cast for 4 weeks. My navicular and ptt continued to be quite painful once the cast was removed. An MRI indicated that I had mild micro tearing. I had a modified kidner four weeks ago after not responding to non invasive therapies. The doctor said that the tearing was much more extensive than indicated on the MRI but he was able to repair the tendon and is confident that I will have a good outcome. He also used an anchor. I am still NWB in a cast. The cast will be removed in a few days, followed by a boot and PT.

Is there a relationship between long standing plantar fasciitis and posterior tibial tendonitis?

I have minimal plantar fasciitis pain following cryo surgery despite having a very thick fascia. Could the fascia continue to thicken and possibly rupture?  

Answer
It is definitely related to the posterior tibial tendonitis. The posterior tibial tendon has a major role in producing the arch on weight bearing
Make sure you can bend your foot at least 10 degrees up from 90 degrees with your knee locked- imagine an L and your foot is the base and your leg with your knee locked is the top part of the L.
Inability to do so may lead to recurrence of the plantar fasciitis. You will need to do calf stretches as part of your physical therapy as soon as you get out of your cast and your doctor gives you the go.
Good Luck Again
Dr George Tsatsos-Chicago & Elmhurst Podiatrist
Board Certified Foot & Ankle Surgery & Orthopedics
NOT ADVICE_JUST INFO FOR ALL