Differences Between Osteoarthritis and Rheumatoid Arthritis

There are a host of different joint problems but when symptoms like joint pain and stiffness persist, most of us worry about arthritis. We often think that arthritis only affects the elderly. This is not true. We tend to believe that arthritis is incurable and will mean a life of disability. But this is not true either. It all depends on what type of arthritis you have. Some are acute while others are chronic. Some can be easily treated or will even resolve on its own without treatment. Others are incurable. Understanding the differences between arthritis is therefore important before reaching conclusions that are can be inaccurate.

Arthritis is a common problem across the globe. It can affect any person of any age or gender. However, arthritis is not a single condition. It is actually a group of conditions involving one of more joints. Arthritis literally means joint inflammation and there are various different types. In terms of prevalence, osteoarthritis and rheumatoid arthritis are the two most common types of arthritis. Osteoarthritis is the most prevalent and rheumatoid arthritis the second most common type of arthritis. Some of the other types include septic arthritis (caused by an infection), post-traumatic arthritis (following an injury) and gout or gouty arthritis (caused by uric acid crystals deposited in the joint).

Joint Structure

Before looking at the differences between rheumatoid arthritis (RA) and osteoarthritis (OA), it is important to have a basic knowledge of the joint anatomy. Joints are the point where two bones meet to allow for movement. There are different types of joint but synovial joints are the most common type in the human body. It also has the greatest degree of movement compared to other types of joints.

The ends of the bones in this type of joint are capped with articular cartilage. It is a tough but flexible tissue that is rapidly regenerated and provides a smooth surface for movement. The joint is lined with a thin membrane known as synovium. It secretes fluid to lubricate the joint (synovial fluid). The entire joint is surrounded by a capsule which strengthens and supports the joint.

Inflammation vs Degeneration

As stated, arthritis means joint inflammation. This is the primary mechanism of rheumatoid arthritis where the joint lining (synovium) is inflamed. However, it can be misleading when it comes to osteoarthritis. Inflammation is mild to absent in most cases of osteoarthritis. The problem is largely degenerative meaning that there is a break down of joint tissue, specifically the articular (joint) cartilage. Over time the cartilage wears down, breaks up and exposes the ends of the bone which it is supposed to protect.

Immune vs Wear and Tear

Rheumatoid arthritis is an autoimmune disease. This simple means that you immune system attacks certain tissues in your body. With rheumatoid arthritis the immune system attacks the lining of the joints and causes inflammation of these joint linings. In osteoarthritis, the cartilage of the joint wears down. Normally this cartilage is constantly replenished but with age or overuse, it cannot keep up with the loss. Eventually it weakens, cracks and erodes. The ends of the bone are exposed and rub against each other.

Patient Age and Gender

Although both types of arthritis can affect any age group, the vast majority of cases of rheumatoid arthritis starts up earlier in adulthood while osteoarthritis tends to arise in the senior years. Rheumatoid arthritis is mainly seen to start in the 20 to 50 year age group. The first stages of osteoarthritis may start as early as the mid 30s but the symptoms only become apparent after 50 years of age. Women are 3 times more likely to have rheumatoid arthritis than men. Women are also more likely to be affected with osteoarthritis than men in the 50s but by the 70s, both men and women are affected equally.

Starts Up Quickly or Slowly

Both rheumatoid arthritis and osteoarthritis are chronic conditions. However, the condition tends to start up more quickly and develop faster in rheumatoid arthritis than osteoarthritis. The problem develops within weeks or months in rheumatoid arthritis compared to years for osteoarthritis. Although the development and progression is much slower in osteoarthritis, there are acute episodes where a patient suddenly develops intense symptoms that can last for a few days to weeks and then ease. These acute episodes do not signal the start of osteoarthritis and are just flareups. It also occurs in rheumatoid arthritis.

Location of Joints Affected

Osteoarthritis is said to mainly affect the larger joints while rheumatoid arthritis occurs in the smaller joints. The hips and knees are commonly affected sites in osteoarthritis. The fingers, wrist and elbows are more commonly affected in rheumatoid arthritis. However, any joint can be affected with either osteoarthritis or rheumatoid arthritis. In the early stages it is thee larger joints in osteoarthritis and smaller joints in rheumatoid arthritis that are primarily affected. The symptoms tend to be the worst at these joints although with time other joints are also involved. In other words, rheumatoid arthritis can affect the knee just as osteoarthritis can affect the wrist.

Joint and Systemic Symptoms

There is pain, tenderness and restriction in movement of the joints in both osteoarthritis and rheumatoid arthritis. Swelling is prominent in rheumatoid arthritis but is rarely present in osteoarthritis. Rheumatoid arthritis tends to involve the small joints of both sides of the  body but osteoarthritis symptoms affect one side more frequently although joints on both sides can be ultimately affected. The symptoms of osteoarthritis are largely confined to the affected joint. While the symptoms in rheumatoid arthritis are most prominent at the joints, this condition can affect other parts of the body outside of the joints.

Joint Stiffness in the Morning

Stiffness of the joints is another major symptom of arthritis. It can occur in both rheumatoid arthritis and osteoarthritis but the presentation does differ to some degree in each condition. In rheumatoid arthritis the joint stiffness is worst in the morning upon waking. It gradually eases within an hour or two as a person moves around. Stiffness in osteoarthritis also occurs in the morning upon waking. It tends to last for a much shorter period than in rheumatoid arthritis but returns with overuse of the joint and by the end of the day. Movement usually eases stiffness in rheumatoid arthritis and while movement may have a similar benefit in osteoarthritis, excessive movement worsens the joint stiffness in OA.