Pharmacy Clinic
Arthritis
ANATOMY OF A JOINT

Rheumatoid Arthritis can affect many joints in the body, including the knee, ankle, elbow,
and wrist. Joints that are actively involved with the disease are usually tender, swollen,
and likely demonstrate reduced motion. To better understand the affects of RA on a
joint, a brief review of a synovial joint follows.


















A synovial joint has the following components:
•        1. A joint capsule that isolates the joint from surrounding tissue.
•        2. A joint cavity formed by the surrounding joint capsule.
•        3. A synovial membrane (synovium) that is the inner lining of the joint capsule.
•        4. Synovial fluid that is secreted by the synovium and serves as a lubricant and
carries nutrients for the joint.
•        5. Bones that come together to form the joint.
•        6. Hyaline (articular) cartilage covers and protects the ends of the bones that
participate in the joint.

There may be other structures present in or near the joint such as disks, cartilage
(menisci), tendons, and ligaments.

Important characteristics of these structures to remember include:
•        1. The joint capsule is composed of two layers, an outer fibrous layer and the
inner synovium identified above. The outer layer has many joint receptors innervating it,
but is not well vascularized. The opposite is true with the synovium, i.e., it is well
vascularized but poorly innervated.

•        2. The articular cartilage has two important functions including the ability to
minimize friction and wear between two opposing joint surfaces during movement and to
dissipate forces on the joint over a wider area, thus decreasing stresses on the
contacting joint surfaces.

•        3. Synovial fluid contains hyaluronate (hyaluronic acid) and a glycoprotein called
lubricin. Both are responsible for the lubrication of the joint, although they are specific
for certain components. Hyaluronic acid is important for the lubrication of the joint
capsule while lubricin is necessary for cartilage on cartilage lubrication.
•        4. Synovial fluid is also the medium by which nutrients are carried to, and wastes
are carried from, the avascular components of the joint.

•        5. The ends of the long bones that form the synovial joints are composed of a
soft, spongy type of bone called subchondral bone. Hyaline (articular) cartilage covers
this bone and protects it. Except for the very ends of the bone, long bones are usually
very strong.

Pathophysiology of Rheumatoid Arthritis "word doc"

Image of Rheumatoid Arthritis

Osteoarthritis

Nonprescription Analgesics