Hydroxyapatite Crystal Deposition Disease (HADD)

Medically Reviewed on 7/10/2023

What is hydroxyapatite crystal deposition disease?

Hydroxyapatite is the major component, and an essential ingredient, of normal bone and teeth. It is hydroxyapatite that makes up bone minerals and the matrix of teeth.

What are hydroxyapatite crystals?

Hydroxyapatite molecules can group together (crystallize) to form microscopic clumps, called hydroxyapatite crystals.

Tiny crystals of hydroxyapatite sometimes form in or around joints and can cause inflammation of joints and tissues around the joints, such as tendons and ligaments. They have been described particularly as a cause of rotator cuff inflammation of the shoulder.

The inflammation caused by hydroxyapatite crystals has been referred to as hydroxyapatite crystal disease.

What causes hydroxyapatite crystal deposition disease?

While not fully understood, the cause of hydroxyapatite crystal disease is believed to be due to the accumulation of small calcium phosphate crystals in the joint tissue.

These crystals may accumulate due to several factors, such as:

  • Age
  • Genetics
  • Joint trauma or injury
  • Underlying medical conditions (such as osteoarthritis, hyperparathyroidism, and hypophosphatemia)
  • Other factors (such as obesity, a diet high in purines, and excessive alcohol consumption)

Is hydroxyapatite crystal deposition disease the same as gout or pseudogout?

No. These conditions are similar in that they are all caused by the inflammation that results from the body's reaction to crystals. However, hydroxyapatite crystals are distinctly different from the crystals of pseudogout or gout. While hydroxyapatite crystals can sometimes also be found in the company of the calcium pyrophosphate crystals characteristic of pseudogout, these are quite different types of crystals.

What are the symptoms of hydroxyapatite crystal deposition disease?

Hydroxyapatite crystal disease (HACD) symptoms vary depending on the location of crystal buildup and the severity.

Common symptoms of HACD may include:

  • Pain
  • Swelling
  • Limited range of motion
  • Stiffness
  • Popping or clicking sounds
  • Weakness

Diagnosis of hydroxyapatite crystal deposition disease

Sometimes, hydroxyapatite crystals can be seen clumped in the fluid of a joint that has developed arthritis. The crystals are usually so small as to be invisible under a regular microscope and thus require a special (electron) microscope for identification.

What is the treatment for hydroxyapatite crystal deposition disease?

The treatment of the inflammation caused by hydroxyapatite crystals includes rest, cold application, and medications to reduce inflammation. Cortisone-related medications injected into inflamed tissues can also sometimes help decrease inflammation and thereby relieve pain.


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Medically Reviewed on 7/10/2023
Medically reviewed by Aimee V. HachigianGould, MD; American Board of Orthopaedic Surgery


Garcia GM, McCord GC, Kumar R. "Hydroxyapatite crystal deposition disease." National Center for Biotechnology Information.