What is Hip Osteoarthritis?

The hip is one of largest, most flexible joints in the body. Lifestyle can be greatly affected by hip arthritis symptoms such as limited range of motion, swelling, and pain in the hip, groin, leg and back. The symptoms may come and go, developing gradually, over months or years.

The most common type of hip arthritis is osteoarthritis. Inflammatory forms of arthritis—such as rheumatoid arthritis, an auto-immune disease, and gout, a metabolic disease—have similar symptoms but are less common.¹ This article focuses on hip osteoarthritis symptoms, risk factors, diagnosis, and surgical and non-surgical treatments.

Osteoarthritis is a degenerative disease signaled by the mechanical breakdown of the joint. Specifically—

• The joint’s cartilage deteriorates, and
• Bones develop osteophytes, or bone spurs, at the joint.

View Hip Osteoarthritis Video

The hip is a weight-bearing joint especially prone to wear and tear. It is the third most susceptible site to develop osteoarthritis, after the hand and knee^{2, 3, 4, 5}. According to the Centers for Disease Control and Prevention (CDC), the lifetime risk of developing symptomatic hip osteoarthritis is 18.5 percent for men and 28.6 percent for women⁶. Health professionals do not know the cause of hip osteoarthritis but have identified several risk factors that increase the likelihood of its development.

There is no known cure for hip osteoarthritis. With a large percentage of the American population aging, health professionals continue to grow and refine knowledge about prevention, diagnosis and treatment options for hip osteoarthritis.

Hip Joint Anatomy

The hip is located where the head of the femur, or thighbone, fits into a rounded socket of the pelvis called the acetabulum. This ball-and-socket construction allows a straight leg to move back and forth and side-to-side, as well as rotate, pointing toes inward and outward.

Both the acetabulum and the rounded femur head are lined with articular cartilage. The articular cartilage is an extremely slippery, strong, flexible material that provides a buffer between the bones as the hip flexes and bears weight.

• See more with Hip Anatomy.

How Hip Osteoarthritis Causes Pain

The articular cartilage in an osteoarthritic hip is thinned, damaged or missing. When hip cartilage has deteriorated:

• New cartilage may be produced, but the new cartilage cells will grow in irregular, bumpy patterns, rather than smooth. The result is that the femur and pelvic bones rub and grind against one another.
• The bones may produce small, scalloped growths called osteophytes or bone spurs, to compensate for the deteriorated cartilage. In turn, the bone spurs can create even more friction.
• Tendons and ligaments can also be stretched or otherwise compromised in an attempt to compensate for the abnormal joint.
• Swelling resulting from osteoarthritis can put pressure on the femoral artery and sciatic nerves traveling through the hip area.

It is interesting to note that while osteoarthritis is referred to as a degenerative disease, it results in the growth of new tissue in the form of osteophytes and irregular cartilage⁷.

These new tissues are not a problem in and of themselves: cartilage does not contain nerve endings that can signal pain to the brain, and osteophytes are considered a normal sign of aging. However, these new tissues don’t effectively protect against friction between bones. Bone-on-bone friction can cause hip pain and other hip joint abnormalities.

References:

1. Lawrence RC, Felson DT, Helmick CG, et al., "Estimates of the prevalence of arthritis and other rheumatic conditions in the United States. Part II," Arthritis and Rheumatism 2008;58(1):26–35.
2. Dillon CF, Rasch EK, Gu Q, Hirsch R., "Prevalence of knee osteoarthritis in the United States: arthritis data from the Third National Health and Nutrition Examination Survey 1991–1994," Journal of Rheumatology, 2006;33(11):2271–2279.
3. Jordan JM, Helmick CG, Renner JB, et al., "Prevalence of knee symptoms and radiographic and symptomatic knee osteoarthritis in African Americans and Caucasians: The Johnston County Osteoarthritis Project," Journal of Rheumatology," 2007;34(1):172–180.
4. Dillon CF, Hirsch R, Rasch EK, Gu Q., "Symptomatic hand osteoarthritis in the United States: prevalence and functional impairment estimates from the third U.S. National Health and Nutrition Examination Survey, 1991–1994," American Journal of Physical Medicine and Rehabilitation, 2007;86(1):12–21.
5. Felson DT, Naimark A, Anderson J, Kazis L, Castelli W, Meenan RF, "The prevalence of knee osteoarthritis in the elderly. The Framingham Osteoarthritis Study," Arthritis and Rheumatism. 1987;30(8):914–918.
6. Murphy et. al, “One in four people may develop symptomatic hip osteoarthritis in his or her lifetime,” Osteoarthritis and Cartilage 18 (2010): 1372-1379
7. Radin, Eric L., “Who Gets Osteoarthritis and Why,” Journal of Rheumatology 31 (2004), accessed online, April 29, 2011, http://www.jrheum.com/subscribers/04/04supp/10.html#2