Research Review by Dr. Shawn Thistle©

Date:

July 2008

Study Title:

A review of plantar heel pain of neural origin: Differential diagnosis and management

Authors:

Alshami AM, Souvlis T & Coppieters MW

Authors’ Affiliations: Division of Physiotherapy, School of Health and Rehabilitation Sciences, University of Queensland, Australia

Publication Information:

Manual Therapy 2008; 13: 103-111.

Summary:

Pain in the heel region is commonly encountered in manual medicine practice. Several conditions can lead to pain in this area including: plantar fasciitis, calcaneal fracture, atrophy of the heel fat pad, and so on. Plantar heel pain may also have a neural origin, including lesions to the tibial, plantar, or calcaneal nerves. These will be the focus of this review.

NERVE ENTRAPMENT SITES

The tibial nerve is the largest distal branch of the sciatic nerve, and it terminates into the following branches: medial calcaneal nerve (MCN) – supplying the plantar surface of the calcaneus, medial plantar nerve (MPN) – supplying the medial aspect of the foot, and the lateral plantar nerve (LPN) – supplying the lateral aspect of the foot. In the literature to date, entrapment of the MCN is well documented as a contributor to heel pain, as well as entrapment of the first branch of the LPN. Tarsal Tunnel Syndrome (TTS) involves entrapment of the tibial nerve at the tarsal tunnel (covered by the flexor retinaculum), and can also cause pain in the heel region.

Entrapment of the 1st branch of the Lateral Plantar Nerve (LPN):
  • the LPN supplies most of the foot muscles and skin on the lateral 1/3 of the foot (including the 4th and 5th toes), anterior to the calcaneus
  • the first branch is also called nerve to abductor digiti minimi, also innervates the flexor digitorum brevis, and quadratus plantae (note, this nerve supplies branches to the calcaneal periosteum, but does not innervate the skin)
  • entrapment normally occurs between the abductor hallucis and quadratus plantae muscles, under the sharp edge of the abductor hallucis deep fascia, or just distal to the medial edge of the calcaneus - entrapment of this nerve is the most common cause of plantar heel pain of neural origin
Entrapment of the Medial Calcaneal Nerve (MCN):
  • normally divides into anterior and posterior branches, which provide sensory innervation to most of the heel fat pad and superficial structures overlying the plantar surface of the calcaneus
  • thought to be the second most common nerve involved in heel pain of neural origin – this nerve is most likely irritated by an atrophied fat pad, but rarely may be compressed between the abductor hallucis, flexor digitorum brevis, and plantar fascia
Entrapment of the Medial Plantar Nerve (MPN):
  • this nerve innervates the abductor hallucis, flexor hallucis brevis, flexor digitorum brevis, first lumbrical, and the skin on the medial 2/3 of the plantar aspect of the foot
  • entrapment of this nerve is not common
Clinical Presentation of Heel Pain of Neural Origin
  • pain is usually characterized as burning, sharp, shooting, shock-like, electric, localized, and may radiate proximally or distally
  • pain is normally worse during or after weight-bearing activities (* see below), and improves with rest
  • pain at night may be severe due to venous stasis and venous engorgement around the nerves
  • * Post-Static Dyskinesia: a common finding with this condition – patients experience severe pain upon rising from bed (thought to be due to fluid pressure build-up around the nerve, which is progressively “milked” out with movement, only to return later in the day)
  • Post-Static Dyskinesia is not pathognomonic for heel pain of neural origin, as it also occurs frequently in patients with plantar fasciitis
  • Sensory Disturbance: is common in Tarsal Tunnel Syndrome (a more proximal entrapment syndrome), but not with entrapment of the first branch of the LPN
CLINICAL EXAMINATION

The following procedures can be utilized to identify heel pain of neural origin:
  • palpation near the medial calcaneal tuberosity and the abductor hallucis (that is, directly over the nerve) is the best way to identify involvement of the LPN
  • MCN involvement can be identified by palpatory tenderness over the medial aspect of the heel fat pad, with distally radiating pain with pressure on the nerve (note: the plantar fascia origin should be pain free to palpation), pain may also be noted near the navicular tuberosity
  • Dorsiflexion/Eversion and Neurodynamic Tests:
    • metatarsophalangeal joints are passively extended while the ankle is held in dorsiflexion and eversion
    • reproduction of the patient’s primary complaint is a positive test
    • it should be kept in mind that extending the toes places extra strain on the plantar fascia origin, which may also aggravate someone with plantar Fasciitis
    • neurodynamic testing involves a sequence of movements to place increasing tension on a neural structure – adding hip flexion to ankle dorsiflexion with the knee extended can increase strain on the nerve, without increasing tension on the plantar fascia
  • Plantar-Flexion/Inversion Test: the foot is plantar flexed and placed into inversion which is thought to increase pressure around the tibial nerve in the tarsal tunnel. A positive test is reproduction of the primary complaint
  • Tinel’s Test: consists of tapping along the course of the tibial nerve – often positive in TTS and may be positive with MCN entrapment
  • electrodiagnostic and quantitative sensory testing may be employed in non-responsive or unclear cases
DIFFERENTIAL DIAGNOSIS
  • Plantar Fasciitis
  • Fat Pad Atrophy: pain is aggravated by hard-soled shoes, and is most intense over the central region of the heel pad; normally the pain does not radiate
  • Tumours: neuromas can occur in all three nerves discussed above
  • other possibilities include: rupture of the plantar fascia, bursitis, fracture, tendinopathy, arthritis, osteomyelitis, and bone cysts
TREATMENT
  • overall, the literature is sparse, resulting in recommendations for treatment similar to that for heel pain in general
  • conservative treatment options include: rest, NSAIDs, corticosteroid injections, shock wave therapy, low level laser, local anesthetic injections, foot orthotics, heel pads/cups, night splints, soft-soled shoes, calf/Achilles stretching, ultrasound, or casting (note: no specific evidence-based recommendations could be provided at this point – more research is required)
  • anecdotally, soft tissue therapies such as Active Release Techniques (ART®) claim success in treating these nerve entrapment syndromes, despite a dearth of published evidence to support their claims

Conclusions & Practical Application:

Nerve entrapment syndromes are an important differential diagnosis for patients with heel pain. Based on the current literature, there is a lack of evidence on treatment approaches for heel pain. However, it is known that the prognosis for this type of pain is good, as most patients improve with conservative treatment.