OA is characterised by the loss of cartilage in synovial joints leading to changes in the periarticular bone.¹ Interestingly there’s more evidence of an inflammatory component to it’s pathology rather than just purely wear-and-tear.
Interesting and important fact:
Only advanced damaged from OA show up on X-rays.¹ Other investigations such as arthroscopy and MRI may be able to show damage in earlier stages.
For more information Listen to the episode:
Kumar P, Clark M (eds.) Clinical medicine. 7th ed. Edinburgh: Elsevier Saunders; 2009. p.518-521.
1. Increase bone resorption leading to rise in calcium and phosphate.
2. Phosphate is filtered in the kidney and it’s resorption is blocked by PTH. This leads to an overall drop in phosphate levels.
3. Calcium is filtered in the kidneys but the resorption is increased by PTH. This leads to an overall increase in calcium concentration.
4. PTH increases Calcitriol (activated Vit D) production in the kidneys. This indirectly increases calcium absorption from the intestines.
FOUR actions of Calcitriol (activated vitamin D)
1. Increases bone resorption causing a rise in calcium and phosphate levels.
2. Calcitriol INCREASES the reabsorption of phosphate in the kidneys.
3. Calcitriol increases the reabsorption of calcium in the kidneys.
4. Calcitriol acts DIRECTLY on the intestines to increase calcium absorption from diet.