What is a calcaneal enthesophyte?

What is a Calcaneal Enthesophyte?

A calcaneal enthesophyte is a bony outgrowth (bone spur) that forms at the insertion site where tendons or ligaments attach to the calcaneus (heel bone), most commonly at the plantar fascia insertion on the inferior calcaneal tuberosity or at the Achilles tendon insertion on the posterior calcaneus. 1

Anatomical Definition and Location

• An enthesophyte forms specifically at the enthesis—the anatomic location where tendon, ligament, or joint capsule fibers insert into bone—distinguishing it from osteophytes which form around joint lines 2, 3

• In the calcaneus, enthesophytes most commonly develop at two sites:

  • Plantar calcaneal enthesophyte (plantar heel spur): Forms at the insertion of the plantar fascia on the inferior calcaneal tuberosity 1
  • Posterior calcaneal enthesophyte (retrocalcaneal exostosis): Forms at the Achilles tendon insertion on the posterior superior calcaneus 4

• The plantar calcaneal spur is a bony outgrowth from the calcaneal tuberosity that has been extensively studied through cadaveric dissection, radiography, and histology 1

Clinical Significance and Associated Conditions

• Calcaneal enthesophytes are commonly associated with enthesitis—inflammation at the tendon or ligament insertion site—which causes the characteristic pain, swelling, and tenderness 2

• Common locations for enthesitis in the heel include the insertion sites of the plantar fascia and Achilles tendons 2

• Important distinction: The enthesophyte (bone spur) itself is not necessarily the source of pain; rather, inflammation of surrounding tissues and possible nerve compression cause the symptoms 5

• Posterior calcaneal enthesophytes are particularly associated with Haglund's deformity, where the prominent posterior superior calcaneus causes inflammation of the overlying retrocalcaneal bursa 6, 5

Risk Factors and Etiology

• Key associations with plantar calcaneal spur formation include age, weight, gender, arthritides (particularly seronegative spondyloarthropathies like psoriatic arthritis), plantar fasciitis, and foot position 1, 2

• Multiple theories explain enthesophyte formation, including degenerative changes, inflammatory processes, traction forces, repetitive trauma, and vertical compression 1

• In psoriatic arthritis specifically, enthesitis represents a hallmark feature of the disease, with the Achilles tendon and plantar fascia insertions being common sites 2

Diagnostic Considerations

• Calcaneal enthesophytes are typically visible on standard radiographs as bony projections from the calcaneus 6, 5

• Clinical presentation varies by location:

  • Plantar enthesophyte: Central or plantar heel pain, worse with first steps in morning or after rest 5, 7
  • Posterior enthesophyte: Posterior and lateral heel pain, particularly with shoe pressure over the prominent bone 6, 5

• Physical examination findings include point tenderness at the specific insertion site and pain with palpation of the affected area 6, 7

Clinical Pitfall

• A critical caveat is that many calcaneal enthesophytes are asymptomatic incidental findings on radiographs—their presence does not automatically mean they are causing the patient's heel pain 5, 1