Complex sentence: Those with plantar fasciitis often have difficulty bending the foot so that the toes are brought toward the shin (decreased dorsiflexion of the ankle) due to tightness of the gastrocnemius muscle or Achilles tendon, which is connected posteriorly to the plantar fascia.
Split into simpler sentences: Those with plantar fasciitis often have difficulty bending bringing their toes toward the shin (decreased dorsiflexion of the ankle). This is usually due to tightness of the gastrocnemius muscle or Achilles tendon, the latter of which is posteriorly connected to the plantar fascia.