I coined the term "treatment triad" for plantar fasciitis a few years back to better describe the disease process and its treatment.
Acute plantar fasciitis is basically a sprain of the fascia, it is an inflammatory condition. It thus can be treated successfully with anti-inflammatories -- oral or injections or cortisone plus the use of soft heel pads or OTC inserts (acute PF can sometimes progress to chronic PF but lets leave that out for simplicity's sake for now).
Plantar fasciitis that persists or becomes chronic does so for one of two reasons....
...abnormal or excessive strain persists on the fascia. This may be due to work conditions, poor shoegear, poor body mechanics: subtalar joint overpronation, midtarsal joint oversupination, tight achille-gastrosoleus.
...tissue quality deteriorates. This can occur due to chronic inflammation which leads to tissue damage, genetic factors leading to poor connective tissue quality or a combination of both.
LEG #1 = inflammation,
LEG #2 = abnormal biomechanics,
LEG #3 = poor tissue quality(degeneration of the tissue due to long term chronic inflammation)
The 3 "legs" of the triad thus have different "height" at different times.
Initially the first leg, "inflammation" is by far the predominant process. As such expect modalities such as cortisone shots to work reasonably well in the first few weeks or few months, then gradually decrease in effectiveness with time. As time goes on and if plantar fasciitis persists, the second leg must be focused on. The body can and does repair itself and if that is not happening then one must remove impediments, ie. find and remove the biomechanical problems preventing that from occurring. Look carefully at the second leg from 6 weeks to 6 months. Inflammation and tissue damage occurring for extended periods of time (say greater than 6 months) will compromise the body's ability to repair tissue. The tissue becomes badly scarred and devascularized. This is the point where the third leg predominates -- tissue quality.
Problematic biomechanics is best treated by a practitioner trained in that area. There are many who dabble in the area of biomechanics, from shoe fitters to retail stores, etc. Expertise in biomechanics is derived from years of study. Biomechanical issues are addressed by changes in shoegear, prescription foot orthotics, manual therapy/physical therapy. Dr. Ed Davis explains how foot orthotics can be effective: https://www.footorthotics.pro/
How is the third leg treated. The term "plantar fasciosis" is a relatively new term that specifically defines this degneration of the fascia. Such degeneration can easily be diagnosed by use of diagnostic ultrasound or sonography. It is important that the presence or absence of fasciosis be established early on so that treatment can be adequately targeted. Surgical release of the plantar fascia was used at this stage but carries a potentially long recovery period as well as what I would consider an unacceptably high complication rate. It has been supplanted by less invasive, safer and more effective treatments to include ESWT (extracorporeal shockwave therapy) and more recently, the Topaz procedure, http://www.topazprocedure.com/, which is also known as a partial fasciectomy via coblation. Coblation is a term meaning "cold ablation" and is a trademark of the Arthrocare Corp.
Now, one caveat, plantar fasciitis often waxes and wanes in the early stages for a number of patients so the "stages" or "legs" I am discussing be affixed to firm time periods. For example, a patient can low grade chronic plantar fasciitis for years, change jobs to one that requires more standing and develops a bout of acute plantar fasciitis superimposed on the chronic process.