A walk though understanding arthritis better
Arthritis is a mix of destruction and healing processes that naturally occur in our bodies, but that has chronically gone wrong
For the purists, here is a definition of osteoarthritis
Osteoarthritic diseases are a result of both mechanical and biological events that destabilise the normal coupling of degredation and synthesis of articular cartilage chondrocytes, extracellular matrix and subchondral bone.
Kuettner KE et al eds. Osteoarthritic disorders, AAOS 1995
In other words.. In normal functioning, there are both destructive (degradation) and healing (syntheses) processes going on. Destructive processes are evolved to tidy up dead and decayed cells that attend normal joint functioning, whilst, healing processes encourage rebuilding and regeneration of constantly stressed working parts of the joint.
The destructive processes are controlled via chemical components like the cytokine, TNF tumor necrosis factor, which stimulates production of IL1 - interleukin 1, another cytokine. IL1 comes from mononuclear cells in the synovial membrane and stimulates the chondrocytes to produce matric metalloproteinases which degrade cartilage. Apart from TNF receptors in the cells, there are also soluble receptors that are free in solution. These mop up excess TNF and so restrict their destructive potency. This is typical of the physiological mechanisms of the body, where the action cause of one chemical is kept in check by another, in a dynamic environment. Here the healing work is done through other cytokines that stimulate TIMP (tissue inhibitor of metalloproteinases), IGF (insulin like growth factor) and TGFB (transforming growth factor beta) that stimulate synthesis of cartilage components.
Damage to the joint happens when healing processes are out balance with destructive ones.
In active diseases like rheumatoid arthritis, this can be very rapid. Personally, I went from moderate stiffness in my hips to intensive pain and the surgeon recommending a double hip replacement within a matter of weeks! At the time, I was 26, and managed to find alternative solution that delayed that need for another nine years. However, more usually, it is thought that one of the factors that bring on osteoarthritis is age related. With advancing age, some of the dynamic mechanisms that maintain the joint become ineffective or even fail, particularly in relation to production of collagen and matrix, leading to arthritic processes being kicked off.
You might have been told "it's just wear and tear", and perhaps you can understand when your health professional needs to give you the quick answer, when pushed for time. However, as we have seen above, this is not all there is to it, if it is that at all.
What specifically shifts the balance between healing and destruction is not known. See below, how joint probems start. It could be that there is a micro fracture, or trauma that leads to increase in enzymatic process. Wear particles of cartilage and matrix causes stimulation of macrophages leading to increase of both IL1 and TNF. These in turn, lead to increase in an inflammatory agent pGE (prostaglandin). Inflammatory processes may further increase breaking down of cartilage.
As we will explore below, once started, the process can spiral with inflammation related joint damage sustaining the disease process. Inflammation itself results in pain and lack of movement. Lack of movement means muscle wastage and more pain from the muscles when you can (occasionally) use them. Additionally, lack of joint movement makes it difficult for nutrients to find it their way into the joint, therefore, further hampering the healing processes.
Examining this process in a little more detail gives us many clues as to how to best manage a progression towards beating the condition and even re-establishing the balance.
How do joint problems start?
