Charcot joint

Bone and joint changes secondary to loss of sensation, as first described by Charcot in 1868. There are 2 major theories regarding the neuropathic joint.

• Neurotramatic theory: the loss of normal proprioception and sensation leads to recurrent trauma, resulting in joint destruction and degeneration. Continued walking on an insensitive joint results in instability and degeneration, sublaxation, and destruction.
• Neurovascular theory: neurally mediated reflex hyperemia causes osteoclastic bone resorption.
• Characteristic associations:
  • 5-15% of patients with diabetes and 20-25% of patients with syringomyelia have Charcot joint.
  • Shoulder – Syringomyelia
  • Hip – Syphilis and Spinal dysraphism
  • Knee – Syphilis and Diabetes
  • Foot and ankle – Diabetes
  • Spine – Spinal dysraphism

• Common causes include diabetes, steroids, alcoholism, trauma, infection, amyloid, tabes dorsalis, syringomyelia, multiple sclerosis, spinal cord compression/malformations, Charcot-Marie-Tooth disease, and connective tissue diseases.
• Hypertrophic changes are caused by upper motor neuron lesions while atrophic changes are due to peripheral nerve injuries.

The imaging findings are as follows:

Plain films are typically sufficient to diagnose Charcot joint, but MR or nuclear medicine studies may be used to exclude septic arthritis.

Neuropathic joints usually follow one of these characteristic forms, or a combination of the 2:

• The hypertrophic joint: joint destruction and fragmentation, osseous sclerosis, and osteophyte formation, similar in appearance to osteoarthritis.
• The atrophic joint: osseous resorption, similar in appearance to surgical amputation or infection.

Radiographic findings in the early stage:

• Joint effusion
• Joint space narrowing
• Soft tissue calcification
• Minimal subluxation
• Preservation of bone density (unless infected)

Radiographic findings in the late stage (i.e. The 6 Ds)

• Increased Density (Subchondral sclerosis)
• Destruction
• Debris (Intra-articular loose bodies)
• Dislocation
• Distention
• Disorganization

Upper extremity changes are less common than weight bearing joints, and are typically due to a syrinx.

MRI can demonstrate soft tissue edema, dislocation, destruction, marrow edema, effusion, and loss of bone definition.

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