Disorders affecting the bones and joints generally fall into three categories; inflammatory, degenerative, and autoimmune.
Autoimmune disorders of the bones tend to be chronic and progressive. These disorders can be difficult to treat. Autoimmune disorders occur when the body’s defense system mistakenly attacks normal cells.
The results can affect not just bones and joints but also other healthy body parts. Some symptoms of autoimmune diseases can be severe.
To help you understand what autoimmune disorders are and how they can affect your bones and joints we’ll start with an explanation of the body’s immune system.
What are autoimmune disorders?
The immune system is one of the body’s defense mechanisms. Autoimmune disorders occur when the immunological system malfunctions.
Immune cells have the ability to attack and destroy invading pathogens and foreign bodies. Immune cells engulf the infecting microorganisms so that they can be easily removed from the body.
The immune system can also trigger the production of antibodies and pro-inflammatory substances that can help in the destruction of the foreign body and restore health. 
If immune cells lose their ability to differentiate between harmful agents and healthy cells, the immune system may attack healthy tissue.
This inability to identify the body’s own tissues marks the beginning of autoimmune disorders. As the immune cells fail to recognize the healthy cells and tissues, they consider them as harmful external agents that must be destroyed.
As a result, the immune system reacts in the same way it would in the presence of pathogens, toxins, and harmful foreign bodies. 
This leads to the release of autoantibodies and pro-inflammatory substances by the immune system in order to destroy the tissues. The autoantibodies attack the healthy cells making their survival difficult.
At the same time, the inflammatory substances cause further damage to these tissues thus accelerating damage to the healthy cells. 
When an autoimmune disorder affects the bones and joints, it results in damage to these tissues. As a result, patients may develop severe pain, swelling, redness, stiffness, and restriction of movements in the affected parts. 
Let’s have a look at autoimmune diseases that can affect the bones and joints.
Autoimmune disorders affecting the bones and joints
1. Rheumatoid arthritis
Rheumatoid arthritis is the most common autoimmune disorder affecting the joints. It usually affects the small joints of the fingers, wrists, and legs.
It occurs due to damage done to the joints because of autoantibodies released by the immune cells. It is a chronic progressive condition that can cause severe pain in the joints with stiffness that can restrict movement.  
Osteoporosis is a bone disorder caused due to the loss of bone mineral density. The risk of osteoporosis is higher in menopausal women. The risk of osteoporosis is higher in certain immunological disorders as a result of decreased absorption of nutrients needed for bone health and the drugs used to treat them.
Autoimmune disorders affecting the digestive system such as Celiac disease can reduce the ability of the intestine to absorb nutrients from food. As a result, the bones are deprived of calcium and vitamin D which are needed for bone formation.
Over time, a deficit of these nutrients can make bones weak and porous, increasing the risk of osteoporosis. 
Crohn’s disease and ulcerative colitis are also autoimmune diseases affecting the digestive tract and can have adverse effects on bones. These diseases prevent efficient absorption of calcium and vitamin D in the intestine.
Additionally, steroidal medications used for treating these diseases can accelerate bone loss. 
Crohn’s disease and ulcerative colitis can increase the risk of osteoporosis.
3. Systemic lupus erythematosus
Systemic lupus erythematosus (SLE) is an autoimmune disorder known to affect the skin, bones, and kidneys. It occurs due to the production of autoantibodies against healthy organs and causes progressive damage. 
Patients with SLE may experience joint pain, stiffness, swelling, redness, and reduced range of motion of the affected joint. 
It has been found that the risk of fractures is higher in patients with diabetes. Type 1 diabetes is an autoimmune disorder that occurs when a person’s immune system attacks their pancreas.
As a result, the production of insulin is reduced. The lack of adequate levels of insulin prevents the efficient metabolism of carbohydrates due to which the blood sugar levels rise in patients with diabetes. 
Diabetic patients tend to have a higher risk of fractures. The hormonal and metabolic changes occurring in the body due to diabetes can inhibit bone formation and suppress bone rebuilding processes. This can make the bones weak and prone to fractures. 
In other autoimmune disorders, long-term steroid treatment can also lead to an increased risk of bone fractures.
5. Thyroid diseases
Thyroiditis is caused by the destruction of the thyroid gland by autoantibodies and can affect bone health. Thyroiditis can create an imbalance in the levels of thyroid hormones and bone remodeling processes are affected. This can increase your risk of osteoporosis. 
6. Parathyroid disorders
Parathyroid hormones play a vital role in regulating the level of calcium in the blood. Autoimmune disorders affecting the parathyroid gland may reduce the availability of calcium to the bones thus reducing bone mineral density. It can make the bones weaker and prone to fractures. 
Some other autoimmune disorders that can affect the bones, muscles, ligaments, and tendons include:
- Autoimmune myositis
- Systemic sclerosis
- Mixed connective tissue disease
- Sjögren syndrome
- Relapsing polychondritis
Autoimmune disorders can affect the routine life of patients. However, it is possible to reduce the complications of these diseases by eating a healthy and balanced diet and exercising regularly.
It is advisable to eat foods rich in calcium, vitamin D, and vitamin C. Calcium and vitamin D helps build strong bones stronger by increasing bone mineral density. Vitamin C, can help regulate the immune system functions and slow down the progress of autoimmune disorders.