The anatomy section mentioned some of the potential problems that can be associated with specific anatomical features. Some categories of hip problems are broader, and these need specific discussion. The different types of arthritis are broad categories of disease, and a full discussion of all of the types of arthritis that have been described could fill several textbooks alone. In fact, a rheumatologist is a specialized internist who treats these problems primarily with medicine (nonsurgical treatment) and accounts for an entire medical subspecialty. However, we will focus on some of the more common and important types which together account for the vast majority of orthopaedic surgery patients.
This chapter discusses the most common types of arthritis and other common causes of hip pain, such as trochanteric bursitis or changes after fractures. True hip joint pain usually presents as groin pain, although occasionally some patients will have primarily buttock or knee pain. Movement of the hip joint typically becomes limited and activities such as putting on socks or clipping toenails becomes increasingly difficult. A limp begins to develop. A small percentage of patients with serious hip disease will actually present with knee pain, which may be due to referred pain because of the overlapping nerve supply. Some types of pain felt around the hip joint may originate from the muscles or other soft tissues outside of the joint itself, such as bursitis. It is also possible that pain in the hip may be completely unrelated to the hip, caused by a lumbar radiculopathy or sciatica (a pinched nerve originating from the spine, usually because of a bulging herniated disc), gynecologic sources, or even a hernia.
This is the “wear and tear” form of arthritis that most patients have. It is often explained to patients as being a gradual wear of the joint (“it's not the years, it's the mileage”), although it typically does not become clinically significant until middle age or later. Nearly all adults over forty will demonstrate at least some osteoarthritis in their joints even though it may not cause pain or problems for many years.
The cartilage coating over the joints wears away, eventually exposing the underlying bony surfaces (analogous to scraping away the Teflon in the frying pan). As this occurs, the body reacts by forming large bone spurs (called osteophytes), extra joint fluid (which may cause an effusion, or joint fluid accumulation), hard underlying bone surfaces (subchondral sclerosis), or cysts around the joint. Eventually, the hip joint begins to resemble a cauliflower more than a smooth, round ball. This usually causes pain in the groin, although it may radiate to the knee, buttock, or side of the hip. The joint becomes progressively stiff, so that it becomes difficult to put on shoes and socks, clip toenails, get up out of a chair, etc.
There is convincing evidence that many patients with osteoarthritis are prone to get it based on their genetics. Some studies involving identical twins suggest that occupation and other factors may not play as great a role as previously thought, and the tendency to develop severe osteoarthritis runs in families. A study recently showed that in identical twins, both usually had similar patterns and severity of osteoarthritis later in life, even if one became a heavy laborer and the other worked at a desk job.
Related forms of osteoarthritis include posttraumatic arthritis (arthritis that forms after an old injury, usually a fracture or a dislocation of the hip), late sequelae or consequences of prior diseases (patients who had slipped capital epiphyses or Legg-Calve- Perthes disease as children), and congenital defects such as a shallow hip socket (hip dysplasia).
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