What Exactly Is A Synovial Joint?
A synovial joint is a bodily joint that is surrounded by pockets of synovial fluid. This fluid acts as a lubricant and aids in the joint’s ability to move freely. Synovial fluid is a thick, viscous substance that serves to cushion the impact of bone movement. In a synovial joint, the related bones are not connected by any solid tissue.
Synovial joints give us the ability to achieve the following motions:
- Extension (straightening out)
- Flexion (bending)
- Rotation (circular movement)
- Adduction (moving in toward your core)
- Abduction (moving outward from core)
There are a variety of synovial joints, found in different areas of the body.
- Hinge Joints – Just like they sound, hinge joints allow a sort of back and forth motion – like a hinge does for a door. The elbow is a hinge joint.
- Saddle Joints – This is a type of joint where the connecting end of each bone is shaped so that one fits inside the other. This kind of joint allows a wide range of motion and is only found in the thumb.
- Ball and Socket Joints – Again, the name says it all. An example of a ball and socket joint is the hips. This kind of joint allows the largest range of motion of any joint type.
- Pivot Joints – Found in the neck, pivot joints allow rotational movement.
- Ellipsoidal Joints – These joints, also called condyloid joints, fit into one another allowing extended motion, but not full rotation. Examples are the fingers.
- Gliding Joints – The bone surfaces connected by these joints ‘glide’ against one another easily, because they have flat surfaces. These joints do not allow rotational movement. A gliding joint in the human body can be found at the wrist.
Synovial joints are composed of three parts:
- Articular capsule – Each synovial joint is completely encased within this pouch.
- Synovial membrane – This tissue lines the articular capsule, and secretes synovial fluid.
- Articular cartilage – This cartilaginous tissue coats the ends of the bones on either side of the synovial joint
While synovial joints are the most common type, there are other kinds of joints in our bodies, like cartilaginous joints and fibrous joints. Fibrous joints are fixed joints, meaning they allow no movement. Examples are the connections between the portions of the cranium. Cartilaginous Joints, like the discs between vertebrae, allow only slight movement.
Synovial Joint Problems
There are painful conditions involving synovial joints that can develop in some individuals. Rheumatoid arthritis usually occurs in synovial joints, which can cause what is known as synovitis. Synovitis is when the synovial membrane becomes inflamed. The lining thickens and the joint fills with fluid, causing pain and limited movement. If you think you have synovitis, see your doctor. He or she can prescribe anti-inflammatory medication and/or cortisone shots. In severe cases, surgery to remove inflamed tissue may be performed.
Since our most active joints are synovial, they are the most likely to become injured. Inflammation and pain from a mild synovial joint injury can usually be overcome with over-the-counter anti-inflammatory medications. If taking anti-inflammatory meds, resting, and using ice packs doesn’t help after a few days then you should seek medical advice. If a joint has been severely damaged, corrective surgery and/or physical therapy may be needed.
Synovial joints can become stressed due to age, weight, or general wear and tear. If you play a sport or work at a job that involves doing the same motion over and over again, you are at risk of developing a joint problem.