Synovial joints – Uric Acid Crystals – by Naveed

A joint is the meeting point of two or more bones. A synovial joint, also known as diarthrosis is one of the most common types of joint found in the human body. Synovial joints are freely movable compared to cartilaginous joints which are partially movable and fibrous joints which do not move. Synovial joints are the most common, including ankles, knees, hips, wrists and shoulders.


The structure of a synovial joint consists of three main parts.


1. The articular capsule is the fibrous capsule that is continuous with the bone.
2. On the inside of the capsule is the second part of the joint known as articular cartilage. The articular cartilage provides the loading and unloading mechanism to resist load and shock on movement or impact.
3. The last part of the joint is the synovial membrane which is the inner layer of the fibrous articular capsule.


Synovial fluid fills the space between the cartilage surfaces and facilitates smooth, painless movement between bones. This clear and slightly viscous fluid is also important because it delivers nutrients and oxygen to the hyaline cartilage, which unlike most body tissues does not have its own blood supply. Any joint movement helps circulate the synovial fluid which in turn feeds the cartilage.


Inefficiency on the part of fluid secretion or blood circulation can therefore trigger problems allowing harmful deposits (e.g. uric acid crystals) to accumulate in synovial joints. If these deposits cannot be removed, inflammation occurs as the body attempts to protect the joint. Chronic inflammation then leads to degenerative tissue changes in the synovial cavity possibly eroding cartilage and allowing the ends of bones to rub together.