Arthritis, Osteoarthritis and Osteoporosis….What’s the Difference anyway?

In this post we will provide some simple definitions for similar sounding terms that are related to the knee joint and overall bone/joint health.

Arthritis

The term simply means an inflammation (-itis) of a joint (arthro-). There are over 100 kinds of arthritis. A joint is an area in the body where two bones meet. In the knee, there are actually three bones which come together. There is the mating of the femur (thigh bone) and tibia (shin bone) forming the tibio-femoral joint and the mating of the femur with the patella (knee cap) forming the patella-femoral joint. Either one or both of these joints can be inflamed and, therefore, be arthritic.

Osteoarthritis

is a specific type of arthritis caused by the breakdown and possibly eventual loss of articular cartilage. Articular cartilage is a special kind of cartilage that covers the ends of the bones where they meet or articulate. In the knee, articular cartilage is found at the mating ends of the femur, tibia and patella. When this cartilage begins to wear down (which can be caused by a number of things such as age and obesity), pain, stiffness, and swelling (arthritis), can occur. This type of arthritis is also called degenerative arthritis, and as the name suggests, usually worsens over time. If it becomes severe enough, Total Knee Replacement may be indicated. For more information, see our section on Osteoarthritis.

Osteoporosis

Unlike arthritis and osteoarthritis, is not related to the joints or joint degradation. It is a change in the actual structure of bone itself. Our bone is a living, dynamic tissue that changes over time. It has a complex structure specifically designed to serve its weight bearing function. Within a long bone like the femur, for example, there are two types of bony structures. Cancellous or spongy bone is found in the interior near the ends of the bones. This type of bone is porous, hence the name. This porous interior is covered by a layer of dense bone known as cortical or compact bone. This bone also forms the hallow shaft of long bones. The picture below shows a cut away view of bone and it various structures.

illu_compact_spongy_bone

In osteoporosis, the major impact on bone is that the porosity of the spongy bone increases. That is, the pores or holes in the “sponge” get bigger. This leads to an overall weakening of the bone and can result in fractures. Common sites for such fractures are the vertebrae, hips and forearm. For more information on Osteoporosis, visit our dedicated section on that topic.

Hopefully these descriptions will clarify some confusion related to these similar terms and conditions.

Comments

2 Responses to “Arthritis, Osteoarthritis and Osteoporosis….What’s the Difference anyway?”

  1. Lisa on February 25th, 2009 8:17 pm

    Good info. I’ve had Rheumatoid Arthritis for 15 years. RA differs from OA, in that it flares in a joint then may go into remission and flare in another joint. But previously flared joints are more likely to re-flare in subsequent flare-up episodes.

    It would be interesting to know if RA responds to surgeries like knee replacements, when that is a frequently recurring joint location for flare-ups.

  2. LS on March 4th, 2009 11:54 pm

    Hi Lisa,

    You might want to visit http://www.hieran.com/knee/ “Robin’s Total Knee Replacement. Robin also has Rheumatoid Arthritis.

    She has had both knees replaced and she shares her personal experience on the site.

    Take care,

    LS

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