Plantar fasciitis is one of the most frequently occurring overuse injury of the foot and characterized by pain under the foot which aggravates during standing, walking and running. A frequently used treatment option for plantar fasciitis is the rocker shoe. The rocker shoe has a proximal apex position and a stiff insole. The rocker shoe is assumed to unload the plantar fascia during gait because it minimizes peak achilles tendon forces and dorsiflexion angles of the toes. However whether a proximal apex position and a stiff insole minimize the strain on the plantar fascia and how these two parameter interact has not been investigated yet.
A musculoskeletal model similar to a previously published study and data from a cadaver study was used to estimate the strain of the plantar fascia in ten healthy young adults and nine patients diagnosed with plantar fasciitis. The participants walked for 60 seconds on their comfortable speed on a treadmill. Four different shoe conditions were randomly applied by varying sole stiffnes and the apex position of the shoe.
Plantar fascia strain remained unaffected by shoe condition, but peak Achilles tendon force, peak MTP1 angle and peak plantarflexion moment were significantly lower when walking with with a proximal apex position and a stiff insole.
Rocker shoes with a stiff insole positively affect peak dorsiflexion angles of the toes and plantar flexion moments but not PA strain during gait. Possibly more proximal apex positions should be used in patients with plantar fasciitis to minimize plantar fascia strain during gait and facilitate healing processes
