OSTEOARTHRITIS

Today I am going to give certain details of the disease process for a lay man to understand In this post the journey to complete understanding of osteoarthritis and its treatment starts with as to how normal joints work, what happens to them in osteoarthritis and which of the body joints are more likely to develop osteoarthritis.

Osteoarthritis is the commonest form of arthritis or joint disease and is a very important cause of pain and disability in advancing years of life. Some degree of osteoarthritis will develop in everyone in old age .Osteoarthritis has no effect on longevity of persons affected with this disease, but can be quite debilitating in terms of limiting activities and diminishing overall quality of life.


How Healthy Joints Work

Joints are parts of body where one bone meets the other and movement occurs such as elbow, knee, hip and ankle. Backbone or spine also has large numbers of small joints, which allow us to move our neck, and back in all possible directions. Ends of bone which meet each other at joint are covered by cartilage. Cartilage is white, smooth, glistening material and is very specialized which functions as a cushioning material and a shock absorber so that hard bones do not rub against each other, and the cartilage also reduces friction during joint movement since its surface is very smooth. In fact no man made material can match the low friction and shock absorbing properties of healthy cartilage in the joint.


Cartilage is made up of tough fibres of a protein called collagen - Enmeshed in these fibres of collagen are the large molecules of another protein called proteoglycan. Proteoglycan molecules contain lot of water in their interior. Water keeps on moving in and out of the domain of proteoglycan molecules almost like water being sucked in and squeezed out of sponge. This property of ability to exchange water so easily gives an elastic characteristic to the cartilage. Collagen fibres give desired strength and proteoglycan molecules allow reversible compression. The combined structure thus makes up for the tough but not too rigid quality needed for this very specialized tissue.



The bone ends with cartilage covering are enclosed in a membrane called synovium. The synovium releases a slippery fluid know as synovial fluid and this fluid further reduces the friction between moving surfaces capped with cartilage and ensures that the joint moves easily and smoothly. The synovial fluid or joint fluid formed by synovial membrane is a special type of fluid that behaves like fluid when the joint is being moved and during walking when the joint is loaded its character changes to something like jelly to act as an additional shock absorber. The synovial fluid nourishes the cartilage. The cartilage has no blood vessels and relies on synovial fluid moving in and out to provide nutrients and take away the waste products.


Ends of bone, cartilage and synovium are further enclosed in a layer of tissue called capsule. Capsule is a thick and strong tissue but is capable of stretching when joint moves. The combination of bone ends with cartilage covering, synovium and capsule is the joint. The joint is further covered by muscles and tendons, which support the joint and also provide the power to move the joint.

What Happens in Osteoarthritis

In osteoarthritis changes occur both in the cartilage and the synovial fluid.The synovial fluid changes in character and composition and it loses its characteristic capacity to behave in a jelly like manner and act as a shock absorber when the joint is loaded. The cartilage therefore has to sustain more load and impact.


At the same time the cartilage also undergoes subtle changes in chemical composition in a way that proteoglycans decrease and water content increases. As a result the collagen fibrils become disrupted and disorganized. The cartilage has now become soft due to disorganization of tight collagen fibrils, and also swollen due to increased water content. It has thus become less resistant to forces gradually develops cracks or fissures, breaks into fragments usually known as fibrillations, becomes thin and completely disappears in places.


Over a period of time most or all of the cartilage covering at the end of bone may disappear. This is seen on x-ray as gradual decrease and then disappearance of joint space. The loss of cartilage leaves the bone end exposed. Similar changes occur on both sides of the joint and therefore now instead of cartilage moving against cartilage, a situation develops where bone is moving against bone. These changes abolish smooth and frictionless movement at the joint. The broken pieces of cartilage and bone fragments lie in the synovial fluid and this irritates synovial membrane to produce more fluid. This fluid, of course, is not of the same composition and physical character as the normal synovial fluid. The joint swells up due to excessive fluid in it.


Bone rubbing against bone, stretching of joint capsule due to excessive fluid and increased friction in the joint, all three elements produce pain and difficulty in moving the joint. This is perceived as stiffness in the joint as the increased effort required to move the joint. Along with this, the range of joint movements becomes less. The bone ends gradually become misshapen and develop bony spurn at the margins called osteophytes. With advancing disease a part of the end of bone may be extensively rubbed of and this produces severe deformity of the joint. The joint deformity is most easily seen at the knee joint. In advanced osteoarthritis of knee the leg does not remain straight but bends to one side commonly towards inside producing bow leg deformity or sometimes bends outwards to produce knock-knee deformity.


Most common joints affected by it are Knee, Hip, Spine and Hands.


Physical therapy can be used to improve strength in the muscles, splinting to support the joint during inflammation, Taping and elecrtic modalities to reduce pain and swelling.



Readers comments are welcome and also if you want me to write about any disorder which you are intrested to know please let me know.