Proximal stability promotes distal mobility and is an adage that we have used time and time again as it holds true for plantar fasciitis as well. Strengthening the hips, as @jfitboyd demonstrates here, is vital.
Regional Interdependence is defined as a SEEMINGLY unrelated impairment in a remote anatomical region contributing to the primary complaints. This concept is especially important when attempting to resolve the POOR BIOMECHANICS that contribute to plantar fasciitis.
Proximal muscle weakness from the gluteus medius, gluteus minimus and quadriceps may contribute to dysfunction at the foot, causing fascia irritation. How?
These proximal muscles assist with the loading response of gait—when the heel first hits the floor—which is necessary for shock absorption. If these muscles are weak, there may be excessive transmission of shock to the structures of the feet rather than dissipation throughout the entire limb.
Furthermore, weakness of the glutes causes an increase in hip internal rotation, as opposed to external rotation. External rotation is necessary for foot supination as it creates a rigid lever needed for propulsion. Poor supination due to prolonged pronation from GLUTE WEAKNESS may cause overstress to the plantar fascia.
This video depicts a great exercise to develop quadriceps and glute strength in a functional manner. Place a theraband above the knees and get into a mini squat position. With one leg forward in a slightly bent position, step back with the opposite leg and then step forward again. The goal is the maintain stability on the stance leg and KEEP TENSION on the outside of the band at all times to sufficiently activate the glutes.