Chondrocalcinosis (plural: chondrocalcinoses) is a descriptive term indicating the presence of gross calcium deposition within articular cartilage, i.e. both hyaline and fibrocartilage.
Chondrocalcinosis articularis was an early term for calcium pyrophosphate dihydrate deposition disease (CPPD) , which may explain the frequent, and factually incorrect equivalence, made between "chondrocalcinosis" and CPPD. These terms are not synonymous.
Subsequent investigation has shown that chondrocalcinosis is somewhat non-specific, for example also seen in advanced osteoarthritis.
It has a reported prevalence of 5-15% and is thought to increase with age.
Chondrocalcinosis, as evident on imaging, represents the macrodeposition of calcium crystals. The calcium crystals are generally composed of either :
- calcium pyrophosphate dihydrate (CPPD) - most common
- basic calcium phosphate:
- carbonate-substituted hydroxyapatite ("hydroxyapatite")
- octacalcium phosphate (OCP)
- tricalcium phosphate
- dicalcium phosphate dihydrate
The underlying mechanism for increased intra-articular accumulation of calcium crystals is not understood .
In addition, the specific role of calcium crystals in the pathogenesis of joint disease remains under investigation. Chondrocalcinosis (presumably representing CPPD) is often asymptomatic, although may be associated with arthritis. Basic calcium phosphate crystals have been shown to provoke inflammatory and cartilage-damaging responses, similar to monosodium urate crystals in gout, and are implicated in Milwaukee shoulder syndrome .
Separately, there is also increasing evidence that basic calcium phosphate crystals are involved in the pathogenesis of osteoarthritis .
In addition to CPPD, chondrocalcinosis may less commonly be a manifestation of other conditions which result in abnormal calcium/phosphate metabolism:
- hypercalcemia, especially hyperparathyroidism
- Wilson disease
- trauma: focal chondrocalcinosis in a traumatised joint
- hydroxyapatite deposition disease (HADD)
See chondrocalcinosis (mnemonic) article for three useful mnemonics.