What Are Calcium Deposits in Your Knees?

Calcium deposits inside the knee is a form of arthritis called pseudogout. Pseudogout erodes the cartilage of the knee and can cause extreme pain.

Calcium Phosphate Crystals

The calcium deposits in the knee are made up of calcium phosphate crystals, which have a regular repeating pattern that sets them apart as calcium and not urate crystals, according to the Arthritis Research Campaign.


Urate crystals are what cause gout, calcium crystals cause pseudogout. The symptoms of calcium on the knee resemble gout. A doctor can take a fluid sample and look under a microscope to determine that the deposits are calcium.

Naturally Occurring

Pseudogout is also known by the name chronic calcium pyrophosphate arthritis. The calcium phosphate crystals that form in the knee are naturally occurring in our body, it is the same substance our teeth and bones are made of. In older individuals, most likely in ill health, the calcium phosphate crystals start to form in other tissues such as the knee, according to the Arthritis Research Campaign.

Sharp Angles

The calcium crystals have sharp angles that are abrasive and grind down the cartilage in the knee.


The calcium deposits crystals cause attacks that inflame the knee joint. The knee becomes hot, swollen and very painful.