Crystals accumulate in the fluid and cartilage of the joints, and cause varying degrees of inflammation and tissue damage.
The diagnosis is confirmed by finding CPP crystals in joint fluid.
Treatment is with medications to relieve the pain and swelling resulting from the inflammation, although none reduce the CPP crystal deposits in the joints.
CPP arthritis usually occurs in older people and affects men and women equally.
Causes of CPP Arthritis
The reason that CPP dihydrate crystals form in some people is unknown. The crystals often occur in people who have the following:
A previous joint injury (including surgery)
Accumulations of an abnormal protein in various organs and tissues (amyloidosis Amyloidosis Amyloidosis is a rare disease in which abnormally folded proteins form into collections called amyloid fibrils that accumulate in various tissues and organs, sometimes leading to organ dysfunction... read more )
An abnormally high calcium level in the blood caused by a high level of parathyroid hormone (hyperparathyroidism Hyperparathyroidism In hypercalcemia, the level of calcium in blood is too high. A high calcium level may result from a problem with the parathyroid glands, as well as from diet, cancer, or disorders affecting... read more )
An abnormally low magnesium level in the blood (hypomagnesemia Hypomagnesemia (Low Level of Magnesium in the Blood) In hypomagnesemia, the level of magnesium in blood is too low. (See also Overview of Electrolytes and Overview of Magnesium's Role in the Body.) Magnesium is one of the body's electrolytes,... read more )
Certain rare disorders including hypophosphatasia, Gitelman syndrome Bartter Syndrome and Gitelman Syndrome In Bartter syndrome and Gitelman syndrome, a hereditary defect of the kidney tubules causes the kidneys to excrete excessive amounts of electrolytes (potassium, sodium, and chloride), resulting... read more , hypophosphatemic rickets Hypophosphatemic Rickets Hypophosphatemic rickets is a disorder in which the bones become painfully soft and bend easily because the blood contains low levels of the electrolyte phosphate. (See also Introduction to... read more , and familial hypocalciuric hypercalcemia Familial hypocalciuric hypercalcemia In hypercalcemia, the level of calcium in blood is too high. A high calcium level may result from a problem with the parathyroid glands, as well as from diet, cancer, or disorders affecting... read more
However, many people with CPP arthritis have none of these conditions. The disorder rarely can be hereditary.
Calcium crystals can frequently occur in joints affected by osteoarthritis Osteoarthritis (OA) Osteoarthritis is a chronic disorder that causes damage to the cartilage and surrounding tissues and is characterized by pain, stiffness, and loss of function. Arthritis due to damage of joint... read more for unclear reasons. However, calcium deposits in a joint may not cause symptoms.
Symptoms of CPP Arthritis
Symptoms of CPP arthritis vary widely. Some people have attacks of painful joint inflammation (arthritis) similar to gout flares, usually in the knees, wrists, or other relatively large joints. Other people have lingering, chronic pain and stiffness in joints of the arms and legs, which may be similar to rheumatoid arthritis Rheumatoid Arthritis (RA) Rheumatoid arthritis is an inflammatory arthritis in which joints, usually including those of the hands and feet, are inflamed, resulting in swelling, pain, and often destruction of joints.... read more or osteoarthritis Osteoarthritis (OA) Osteoarthritis is a chronic disorder that causes damage to the cartilage and surrounding tissues and is characterized by pain, stiffness, and loss of function. Arthritis due to damage of joint... read more .
Compared to gout flares, attacks from CPP arthritis vary more in intensity, tend to last longer, and are often more difficult to treat. As in gout, CPP arthritis attacks can cause fever. Some people have no pain between attacks, and some have no pain at any time, despite large deposits of crystals.
Unlike in gout, where collections of crystals often occur in tissues near joints, people with CPP arthritis rarely develop hard lumps of crystals (tophi).
Diagnosis of CPP Arthritis
Microscopic examination of joint fluid
Sometimes x-rays or ultrasonography
Doctors suspect CPP arthritis in older people with arthritis, particularly when joints are intermittently swollen, warm, and painful. Doctors confirm the diagnosis by removing a fluid sample from an inflamed joint through a needle (joint aspiration Joint aspiration (arthrocentesis) A doctor can often diagnose a musculoskeletal disorder based on the history and the results of a physical examination. Laboratory tests, imaging tests, or other diagnostic procedures are sometimes... read more ). CPP dihydrate crystals are found in the joint fluid. They can be distinguished from uric acid crystals (which cause gout) using a special microscope with polarized light.
X-rays X-rays A doctor can often diagnose a musculoskeletal disorder based on the history and the results of a physical examination. Laboratory tests, imaging tests, or other diagnostic procedures are sometimes... read more may show masses of crystals in a joint's cartilage suggests the diagnosis. Ultrasonography Ultrasonography A doctor can often diagnose a musculoskeletal disorder based on the history and the results of a physical examination. Laboratory tests, imaging tests, or other diagnostic procedures are sometimes... read more of the joint may show crystals in joint cartilage and strongly suggests the diagnosis of CPP arthritis.
Prognosis for CPP Arthritis
Often, the inflamed joints heal without any residual problems. However, in some people, chronic arthritis and permanent joint damage can occur over time, with some joints so severely destroyed that they can be confused with neurogenic arthropathy Neurogenic Arthropathy Neurogenic arthropathy is caused by progressive joint destruction, often very rapid, that develops because people cannot sense pain, continually injure joints, and thus are not aware of the... read more (Charcot joints).
Treatment of CPP Arthritis
Drainage of joint fluid and injection of a corticosteroid
Medications to relieve pain and swelling resulting from inflammation
Treatment of acute CPP arthritis is similar to that for acute gout Treatment Gout is a disorder in which deposits of uric acid crystals accumulate in the joints because of high blood levels of uric acid (hyperuricemia). The accumulations of crystals cause flares (attacks)... read more . Usually, treatment can stop acute attacks and prevent new attacks but cannot reverse changes in already damaged joints. Excess joint fluid can be drained and a corticosteroid can be injected into the joint to rapidly reduce the inflammation and pain.
Medications taken by mouth help treat CPP arthritis. Most often, nonsteroidal anti-inflammatory drugs Nonsteroidal Anti-Inflammatory Drugs Pain relievers (analgesics) are the main drugs used to treat pain. Doctors choose a pain reliever based on the type and duration of pain and on the drug's likely benefits and risks. Most pain... read more (NSAIDs) are used to promptly stop the pain and inflammation of acute attacks.
Colchicine (see table ) can be given by mouth in daily low doses (usually 1 or 2 pills) to try to limit the number of flares.
Corticosteroids taken by mouth are effective at treating acute CPP arthritis flares and are particularly useful for some people who should not take NSAIDs or colchicine.
If people cannot tolerate corticosteroids, NSAIDs, or colchicine, drugs that suppress the immune system and inflammation (such as anakinra daily injections) can be effective.
Unlike for gout, no specific effective long-term treatment of CPP arthritis is available. However, physical therapy (such as muscle-strengthening and range-of-motion exercises) may be helpful to maintain joint function.