What is Charcot Joint?
Charcot joint, also known as neuropathic arthropathy, is a condition characterized by loss of sensation in the different joints of the body. It was first described by a French neurologist, Jean-Marie Charcot in 1868. 
This disorder is most commonly observed on diabetic patients who have had uncontrolled blood sugar levels for more than 10 years. Aside from loss of sensation, it is also characterized by instability of the affected joint. The loss of sensation increases the risk of patient experiencing accidents which can lead to further joint injury. 
The affected joint is dependent on the location of the nerve damage. In most cases, the weight-bearing joints such as the knee, ankle and spinal cords are involved. For those who have diabetes, injury to the ankle joints and other foot joints are the most common complaints because minor stimulus-causing pain is not easily felt. 
Causes of Charcot Joint
- A potent nerve supply is highly important for the function of a joint. If the nerve supply is interrupted, it leads to degeneration of the cartilage which further results to bone fracture. As the loss of sensation aggravates the joint swells and gets distorted as well. 
- The joint that is affected is a good starting point when identifying the cause of this disorder. It is possible that multiple joints are affected but having three affected joints at one time is highly unlikely.
Syringomyelia injures the wrist joint more while tabes dorsalis commonly affects the hip, knee and spine.
- Congenital sensitivity to pain targets the knee while diabetes can affect multiple joints such as the wrist, ankle, foot and spine. Other causes can include spinal cord injury, syphilis, steroid use, spina bifida and, scleroderma.
Pathology of Charcot Joint
Charcot joint can occur in two forms: atrophic or hypertrophic. Some experts say that both forms actually present on the patients, only that the atrophic form occurs earlier.
Picture : Charcot Joint of the Elbow
- Atropic form. This is the more common form and occurs mainly on the upper limb joints such as the elbow.  In this form, there is observable reduction on the bone mineral density (BMD) and the amount of proteins stored in the bone. The bone undergoes resorption with no visibility of spurs and fragments.
Picture : Charcot Joint of the Shoulder
- Hypertropic form. Unlike atropic form, there is no osteoporosis seen on this form but bone fractures and dislocations are noticeable in X-ray.
Charcot Joint Classification
Brodsky anatomic classification of Charcot arthropathy
source : ncbi.nlm.nih.gov
The modified Eichenholtz classification
source : ncbi.nlm.nih.gov
Charcot Joint and Radiology
Radiology has been a good advancement in the medical field. This field made it possible for medical professionals to look at the internal parts of the body without invasive procedures. However, there is challenge on the diagnosis of charcot joint using radiology as almost all of the findings for this disorder can also be found for other disorders such as osteomyelitis.
Picture : Charcoat joint of the knee joint
This allows physicians to look at the general condition of the bones. The above picture shows marked hardening of the tissue, fragmentation and destruction of the joint.
This procedure allows physicians to check for infection and secure samples for further analysis.
Computed Tomography (CT) Scanning
This procedure is used to evaluate destruction of the cortex, separation of a piece of the dead bone, presence of intraosseous gas.
Magnetic Resonance Imaging & radionuclide scanning
These procedures are helpful in differentiating infection versus osteomyelitis. 
This X-ray image shows extensive resorption on the affected portion while bone mineralization is maintained for the remaining viable part of the humerus.
This image shows the chest radiograph of a 28-year-old patient who was diagnosed with neuropathic osteoarthropathy. The arrow pointing to the right shows the destruction of the glenohumeral joint, which can be asymptomatic. 
How do we Treat Charcot Joint?
Medical Therapy consists of two phases: acute and post-acute phase.
- The acute phase is comprised of immobilization through casting and reduction of stress. A study has shown that acute phase can last more than 3 months, in which time the patient is advised not to bear weight on the affecting joint. Not doing so will increase the length by which the patient needs to wear the cast. The cast needs to be checked and replaced at regular timings. Additional care must be done in cases of ulceration.
- After the cast is removed, the patient will need to wear a brace to protect the joint. Braces come on different types depending on the specific need they address. There are patellar tendon-bearing brace, double metal upright AFO and more. Patients will also be advised to use custom footwear as the normal footwear may lead to the recurrence of the disorder. In total, the healing process can take up to 2 years.
There are also surgical procedures available for the management of Charcot joint. These include the following:
- Exostosectomy of the bony prominence – removal of a non-cancerous growth on the bone surface
- Osteotomy – shortening, lengthening or changing of the alignment of the bone 
- Arthrodesis – fixation of a joint to encourage bone fusion
- Screw and plate fixation
- Open reduction and internal fixation
- Reconstructive surgery
- Fusion with Achilles tendon lengthening
- Autologous bone grafting
If fractures are left untreated, they can cause infection which can require amputation. Other complications include the formation of clubfoot, rocker-bottom foot, and plantar arch inversion, ligamentous ossification, extra-articular exostoses and even osteomyelitis.
It is important that a patient with the risk factors listed above visit a licensed physician to ensure that the condition is treated and managed, if not prevented.