Is plantar calcaneal enthesopathy caused by arthritis?

Plantar Calcaneal Enthesopathy and Its Relationship to Arthritis

Plantar calcaneal enthesopathy is commonly caused by inflammatory arthritis, particularly psoriatic arthritis, which is characterized by inflammation at the entheses (where tendons and ligaments insert into bone). 1

Relationship Between Enthesopathy and Different Types of Arthritis

Psoriatic Arthritis

Psoriatic arthritis (PsA) is strongly associated with plantar calcaneal enthesopathy:

• Enthesitis is a distinguishing feature of PsA, with the heel being the most common location at both Achilles and plantar fascia insertions 2
• The prevalence of PsA among psoriasis patients is 30%-33%, with enthesitis being a key manifestation 1
• In PsA, the enthesis is the anatomic location where tendon, ligament, or joint capsule fibers insert into the bone 1
• Common locations for enthesitis in PsA include:
  • Insertion sites of the plantar fascia
  • Achilles tendons
  • Ligamentous attachments to ribs, spine, and pelvis 1

Seronegative Spondyloarthropathies

Seronegative spondyloarthropathies, including PsA, reactive arthritis, ankylosing spondylitis, and arthritis associated with inflammatory bowel disease, commonly present with enthesitis:

• These conditions are characterized by findings related to erosions, enthesitis, and bone proliferation 1
• Local treatments for calcaneal enthesopathy in seronegative spondylarthritis include glucocorticosteroid injections, which have shown the best effect 3

Osteoarthritis

The relationship with osteoarthritis is more complex:

• Calcaneal enthesophytes are associated with foot osteoarthritis but not hand osteoarthritis 4
• This pattern suggests a local, biomechanical rather than systemic bone-forming process in osteoarthritis 4
• Enthesopathy at the superior or inferior surface of a calcaneus may be seen in normal individuals with degenerative osteoarthrosis 5

Diagnostic Considerations

Clinical Presentation

• Pain, swelling, and tenderness at the enthesis site
• Morning stiffness lasting longer than 30 minutes is a valuable indicator when considering the diagnosis of inflammatory arthritis 1
• Dactylitis ("sausage digit") may be present, which is a combination of enthesitis and synovitis involving a whole digit 1

Imaging

For suspected enthesopathy:

1. Plain radiographs - Initial imaging modality

   • Can show erosions, enthesitis, and bone proliferation in spondyloarthropathy 1
   • May reveal calcaneal spurs, which are more common in PsA than controls 2
   • Fluffy plantar periostitis is a distinctive feature of inflammatory spurs in PsA 2

2. MRI - If radiographs are negative or equivocal

   • Shows cortical erosions, synovial hypertrophy, and soft tissue abnormalities 1
   • Can detect bone marrow edema and increased fluid signal at enthesitis sites 1
   • Currently considered the most sensitive imaging study for plantar fasciitis 1

3. Ultrasound

   • Can identify synovial hypertrophy and blood flow on color Doppler imaging 1
   • Good sensitivity (80%) and specificity (88%) in diagnosing plantar fasciitis 1

Treatment Approach

For enthesopathy related to inflammatory arthritis:

1. Treat the underlying inflammatory condition

   • In peripheral arthritis associated with inflammatory conditions, treatment of the underlying disease is normally effective in relieving symptoms 1

2. Local treatments

   • Glucocorticosteroid injections into the calcaneal region have shown the best effect for calcaneal enthesopathy in seronegative spondylarthritis 3
   • Laser therapy or hydrocortisone phonophoresis is recommended when pain is the dominant symptom 3

3. Physical therapy and supportive measures

   • Intensive physiotherapy may be beneficial, especially in axial arthropathy 1

4. Advanced therapies

   • For persistent symptoms, especially in PsA, biologic agents targeting TNF or IL-12/23 may be necessary 1

Distinguishing Features of Inflammatory vs. Non-inflammatory Enthesopathy

• Inflammatory enthesopathy (as in PsA):

  • Fluffy plantar periostitis on radiographs 2
  • Longer mid-segment and broader base of calcaneal spurs 2
  • Morning stiffness lasting >30 minutes 1
  • Response to anti-inflammatory treatment

• Non-inflammatory/mechanical enthesopathy:

  • Often related to repetitive microtrauma
  • Stiffness tends to occur with joint activity rather than in the morning 1
  • May be associated with local factors like obesity or foot mechanics

Conclusion

Plantar calcaneal enthesopathy is frequently caused by inflammatory arthritis, particularly psoriatic arthritis and other seronegative spondyloarthropathies. The presence of enthesitis at the calcaneus should prompt evaluation for underlying inflammatory conditions, especially when accompanied by other features such as morning stiffness, dactylitis, or characteristic radiographic findings.