Misdiagnosis of Enthesitis-associated Pathology as Small Joint Septic Arthritis or Osteomyelitis


Bone infections are termed osteomyelitis and primary infections within the joint space are termed septic arthritis.

This page has been inspired by doctors who have attended lectures given by the site creators. These doctors confessed that they had seen cases where fingers and toes were operated on based on lack of knowledge about enthesitis related pathology.

The authors have also personally seen young patients who were treated for months with antibiotics without benefit where significant joint damage resulted.

Case Illustrations

On magnetic resonance imaging both bone infections termed osteomyelitis and enthesitis related pathology can look very similar.

Both infectious arthritis and Enthesitis related arthritis including Psoriatic Arthritis can have extensive soft tissue and bone inflammatory changes.

In early disease the enthesitis related pathology usually has good preservation of the joint surface also called the bone cortex.

On a type of magnetic resonance imaging called fat suppression techniques excessive accumulation of water in the bone gives a white colour or what is termed "high signal." This can be seen following bone injury, fracture, related to enthesitis and other entities such as joint infection and especially bone infection called osteomyelitis. This is an example of a bone infection or osteomyelitis. Part of the treatment of this may include an operation to drain and irrigate the bone
This is a case of acute Psoriatic Arthritis. There is severe inflammation of the entheses on the left and severe soft tissue fluid accumulation. Additionally there is very extensive inflammation within the bones. As can be seen from these images the magnetic resonance imaging appearance of bone infection and enthesitis related arthritis can be remarkably similar

Tips for Diagnosis

Enthesitis related arthritides may not have tell tale signs of enthesitis that a doctor can feel because the insertons are too small to feel.

Carefully check for a history of psoriasis in the patient or in the family.

Both osteomyelitis and Psoriatic Arthritis can be associated with preceding trauma so the history of trauma should not be used to dismiss Psoriatic Arthritis.

Radiologists and surgeons need to consider enthesitis related arthritis as possibilities.