Every day, people come to orthopaedic surgeons because of “hip pain”. But often, what they are calling hip pain is not true hip pain. How can this be? It is because what most people call the hip is not the hip joint. The hip joint is a ball and socket, and it is located in the groin. The place that most people call the hip is on the side, at or below the belt line, where they put their hands when they stand with their hands “on their hips”, where a mother carries a baby on her “hip”, where the hip pockets of pants are, or where a policeman carries his pistol in a “hip holster”. If you ask people to point to their hip joint, many will point to that area on the side, not to the groin. We can speak of hip pain, therefore, as being either “true” hip pain—that is, coming from the hip joint itself—or “false” hip pain—that is, coming from another source.
True Hip Pain
True hip pain is most commonly felt in the groin, because that is where the hip joint is. Sometimes it is felt also in the thigh or knee because of what is called referred pain, which is pain felt in a place other than at the source of the pain. True hip pain is often accompanied by limping and decreased motion of the hip joint, causing the patient to have difficulty reaching his or her foot to cut toenails or tie shoes.
The most common cause of true hip pain is osteoarthritis, which is the most common joint disorder in the world, affecting more than 50% of people by age 65, and 80% by age 75. It most often occurs in knees, hips and hand joints, and less often in other joints. It causes destruction of joint cartilage, which is the smooth, slippery surface covering the ends of the bones. You can see joint cartilage on the ends of a chicken bone. As long as it stays smooth and slippery, joint motion is full and comfortable. Osteoarthritis causes the cartilage to become soft and rough and to disintegrate, causing the joint to get painful and stiff. If the pain is not too bad, it can be managed with over-the-counter or prescription pain relievers and a cane. In some cases, a relatively new, minimally invasive operation called hip arthroscopy can help by recontouring and rounding the bones of the ball and socket if they have started to become deformed as part of the osteoarthritic process. If the pain becomes too severe for the patient to tolerate, which is a common scenario, total hip replacement can be done. Total hip replacement is one of the most common operations in the world, and one of the most successful, achieving in the great majority of cases complete relief of pain and restoration of normal walking and daily activities.
Another relatively common cause of true hip pain is a torn acetabular labrum. The acetabular labrum is the rubbery cartilage rim of the hip socket, and it can become torn in slightly aging athletes doing vigorous sports, resulting in sharp groin pain with certain motions of the hip joint. If it gets bad enough, that pain can often be greatly relieved by hip arthroscopy to repair or remove the torn cartilage.
Other causes of true hip pain include other kinds of arthritis, such as rheumatoid arthritis, and other conditions such as avascular necrosis and infection. Avascular necrosis of the hip is death of the femoral head (the “ball” of the ball and socket hip joint) from loss of blood supply. It can occur in people who have taken steroid medication for a long time, alcoholics, and after a femoral neck fracture or hip dislocation. Rarely, it occurs spontaneously in young children, in which case it is called Perthes’ disease. Infection in the hip joint can occur at any age, but is most common in infants and very young children, and causes fever and extreme pain. In young adolescents, a somewhat uncommon condition called slipped capital femoral epiphysis occurs, causing true hip pain and limping. As a rule, sometimes with the exception of Perthes disease, these conditions will require surgery. Occasionally, runners will develop a stress fracture of the femoral neck, resulting in groin pain and limping. These stress fractures usually heal by themselves with time and rest from running.
False Hip Pain
The most common cause of false hip pain, which is felt in the side or back of the “hip” region, is referred pain from the lumbar spine (the lower back part of the spine), and it is more common than true hip pain. The most frequent causes of this pain originating in the lumbar spine are disc degeneration resulting in bulging or herniation of discs—either acute or chronic—and arthritic changes in the small spinal joints called facet joints. These spinal conditions usually cause low back pain, and very often cause pain in the “hip”, groin, buttock, and thigh or farther down the leg. This pain in these areas other than the lower back occurs either because of referred pain or because of radicular pain (sciatica) caused by pressure on a spinal nerve root from a herniated disc or the bone spurs of an arthritic facet joint.
The good news about pain coming from the lumbar spine, including false hip pain, is that it usually goes away, either by itself or with help from doctors and physical therapists consisting of advice about posture and body mechanics, pain-relieving exercises and sometimes medications. Many patients have gone to see an orthopaedic surgeon complaining of severe “hip” pain, fearing that they might be heading for a hip replacement, and have been greatly relieved to find out that the culprit is not the hip joint but the lumbar spine, and that relief can be expected.
Another, less common, cause of false hip pain is trochanteric bursitis, which causes pain and tenderness over the bony prominence on the side of the hip region, often because of prolonged sitting which puts pressure on that spot. It is commonly very long-lasting but not permanent, and can usually be relieved by changing one’s sitting posture and the type of chair one uses, by physical therapy, and/or by a cortisone injection.
An even less common cause of false hip pain is polymyalgia rheumatica, which can cause vague and diffuse pain and stiffness around the hip and shoulder regions, among other symptoms. It is a vascular inflammatory disease, which can be very effectively treated with oral steroids.
Severe or persistent “hip” pain is a good reason to see a primary care doctor or orthopaedic surgeon. By means of a history and physical examination, and sometimes x-rays and other tests, the doctor can diagnose and treat the problem with a high likelihood of success.
