The plantar fascia is composed of sheets of dense collagen bundles located between the skin and superficial muscle layer of the plantar foot. It functions to provide static and dynamic support to the longitudinal arch of the foot. This aponeurosis shares an origin off the anteromedial plantar aspect of the calcaneal tuberosity with the flexor digitorum brevis (deep) and abductor hallucis (medial). Thereafter, the fascia divides into several fibrous slips which insert on the plantar plates of the metatarsophalangeal joints, bases of the proximal phalanges, and the flexor tendon sheaths.

Biomechanically it acts to provide support to the arch of the foot both dynamically and statically. Plantar fascial tension is generated from it being wound around the metatarsal heads to generate a windlass mechanism. Metatarsophalangeal joint dorsiflexion during toe off tensions the plantar fascia, which aids to lock the transverse tarsal joint and provide the stable lever arm needed for efficient gait. Cadaveric studies have shown that transection of the plantar fascia leads to a loss of longitudinal arch height during terminal stance. Plantar fascia transection also alters pressure distribution of the forefoot, thereby increasing the load on the second metatarsal.^{1, 2}

Plantar fasciitis is thought to be the most common cause of plantar heel pain. Other pathologies on the list of differential diagnoses include heel fat pad atrophy, calcaneal stress fractures, and compression neuropathy of the first branch of the lateral plantar nerve. Epidemiologically, men and women are affected equally. Risk factors for developing the disorder include obesity, heel cord tightness, prolonged weight bearing, and repeated trauma on hard surfaces (e.g., road running). The pathogenesis is thought to be repetitive microtears and chronic inflammation of the plantar fascia at its origin.³

Classically, patients give a history of “start-up pain” localized to the medial plantar heel. The pain is worse with the first few steps after getting out of bed or after sitting for a protracted period. At rest, the foot is relaxed in plantar flexion with the metatarsophalangeal joints in slight flexion, resulting in minimal tension on the plantar fascia. When arising from a non-weightbearing position, tension is applied to the plantar fascia leading to microtears and resultant pain. Each time the patient arises after a prolonged time off their feet this process recurs resulting in a chronic nonhealing pathology. Additionally, activity-related plantar fasciitis is often increased with repetitive loading of the heel and toes, especially when performed on hard surfaces.

Physical examination reveals a point of maximal tenderness at the proximal medial origin of the plantar fascia. The trigger point is usually just distal to the area where the soft skin of the medial hindfoot transitions to the thicker, tougher plantar skin on the medial heel. A classic history in conjunction with this finding is generally sufficient to make the clinical diagnosis of plantar fasciitis. Additional workup is rarely necessary for acute plantar fasciitis.

Recalcitrant plantar fasciitis nonresponsive to conservative intervention merits further workup. Routine radiographs are used as a primary investigation of the affected extremity and can be useful to rule out other etiologies of heel pain. Radiographs are also used to assess for predisposing anatomical deformity, or to identify calcification at the origin of the plantar fascia. However, it should be noted that one study looking at radiographs of a random sample of patients encountered a heel spur in 13% of subjects while only one-third of the spurs detected were symptomatic.⁴ Ultrasound has been shown to be useful in identifying plantar fasciitis when the proximal plantar fascia thickness measures greater than 4 to 5 mm.^{5, 6} Ultrasound may also be helpful in following treatment as subjective improvement from conservative therapy has been correlated with thinning of the plantar fascia.⁷ Magnetic resonance imaging (MRI) has also been demonstrated to be useful to measure the plantar fascia thickness, intra- or perifascial edema, fascial tears, and calcaneal edema suggestive of enthesopathy.^{8, 9} The improved soft tissue detail appreciated with MRI can be used to help rule out more rare soft tissue disorders such as a tumor or abscess.