Charcot joint

Charcot joint, also known as a neuropathic or neurotrophic joint, refers to a progressive degenerative/destructive joint disorder in patients with abnormal pain sensation and proprioception.

Epidemiology

In modern Western societies by far the most common cause of Charcot joints is diabetes, and therefore, the demographics of patients matches those of older diabetics. Prevalence differs depending on the severity of diabetes 10:

  • ~0.1% in general diabetic population
  • ~15% in high-risk diabetic population
  • ~30% in patients with peripheral neuropathy

Clinical presentation

Patients present insidiously or are identified incidentally, or as a result of investigation for deformities. Unlike septic arthritis, Charcot joints although swollen are normal temperature without elevated inflammatory markers. Importantly they are painless. 

Pathology

There are two forms of Charcot joint: atrophic and hypertrophic. Charcot joints are typically unilateral but are bilateral in ~20% (range 5.9-39.3%) of cases 10.

The pathogenesis of a Charcot joint is thought to be an inflammatory response from a minor injury that results in osteolysis. In the setting of peripheral neuropathy both the initial insult and inflammatory response is not well appreciated, allowing ongoing inflammation and injury 10.

Atrophic form
  • most common form 1
  • occurs earlier 2
  • has an acute progression
  • characterised by reabsorption of the ends of the affected bone
  • joint destruction with resorption of fragments
  • absence of osteosclerosis and osteophytes
  • mainly occurs in non-weight bearing joints of the upper limb 1
Hypertrophic form
  • only sensory nerves affected
  • slow progression
  • joint destruction with periarticular debris/bone fragmentation
  • initially widened then narrowed joint space
  • presence of osteosclerosis and osteophytes 1
  • absence of osteoporosis (unless joint is infected) 3
Aetiology

These can be recalled with the "S" mnemonic.

Location

The involved joint is highly suggestive of the aetiology:

Radiographic features

Radiograph and CT

General characteristics include (six Ds mnemonic) 1:

  • dense bones (subchondral sclerosis)
  • degeneration
  • destruction of articular cartilage
  • deformity (pencil-point deformity of metatarsal heads)
  • debris (loose bodies)
  • dislocation
MRI
  • content pending

Differential diagnosis

Imaging differential considerations include:

History and etymology

Jean-Martin Charcot was the first person to give a detailed description of the neuropathic aspect of this condition in 1868 in a patient suffering syphilis.

Practical points

Useful MRI features that support superimposed osteomyelitis on a Charcot joint include 4:

  • sinus tract
  • diffuse marrow signal abnormality
  • replacement of soft tissue fat
  • thick rim enhancement
  • joint erosion

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