Osteoarthritis is due to wear of the joint surfaces. As we get older your joints start to wear in a similar fashion to parts within a well used machine. There can be factors which accelerate or predispose your parts to wear but ultimately all our joints will show some signs of wear.
So, how does a normal joint progress to an osteoarthritic joint? The points below are listed in chronicological sequence and help explain what happens (step by step) and also how it links to our symptoms we present with:
1) General wear and tear
The surface cartilage starts to show signs of weakening due to lifetime of use
2) Cartilage swelling (symptoms = pain on activity, relieved by rest)
Weight bearing activity causes the weakened cartilage to start swelling.
3) Joint narrowing (symptoms = stiffness and pain)
Swollen, weakened cartilage starts to wear causing the joint space to decrease.
4) Breakdown (symptoms = swelling and clicking)
The continued wearing causes cartilage particles within the joint and an irregular joint surface
5) Compensation (symptoms = enlarged joint)
As the joint becomes painful, we use it differently. This leads to new bone growth on the joint margins
6) Bone Exposure (symptoms = night pain and deep aching)
The cartilage covering is completely worn away, leading to exposed bone.