Transient osteoporosis of the hip is an uncommon condition that causes temporary bone loss in the upper portion of the thighbone (femur).
People with transient osteoporosis of the hip will experience a sudden onset of pain that intensifies with walking or other weight-bearing activities. In many cases, the pain increases over time and may become disabling.
Painful symptoms gradually subside and usually end within 6 to 12 months. Bone strength in the hip also returns to normal in the majority of people.
Despite the name, transient osteoporosis of the hip is very different from the more common age-related osteoporosis. Age-related osteoporosis is a painless, progressive condition that leads to a weakening of the bones throughout the body. Unlike transient osteoporosis, it can put people at greater long-term risk for fractures in different areas of the body.
For more information about age-related osteoporosis: Osteoporosis
The hip is one of the body’s largest joints. It is a ball-and-socket joint. The socket is formed by the acetabulum, which is part of the large pelvis bone. The ball is the femoral head, which is the upper end of the femur (thighbone).
In transient osteoporosis of the hip, the femoral head loses density and strength.
Transient osteoporosis of the hip is an uncommon condition that most often occurs in young or middle-aged men (between ages 30 and 60), and in women in the late stages of pregnancy (the last 3 months) or in the early post-partum period.
Transient osteoporosis most often occurs in the hip joint, but can also affect other joints in the leg, such as the knee, ankle and foot.
During the time that the bone is weakened, it is at greater risk for breaking.
Currently, there is no clear explanation for what causes this condition. Researchers are studying this disease and several theories have been proposed, although none are proven.
Some of the causes that have been suggested include:
Because transient osteoporosis of the hip is not a common condition, doctors often diagnose it by ruling out other, more frequent sources of hip pain. Arthritis, osteonecrosis, stress fracture, muscle injury, and tumor are all conditions that your doctor may consider during your evaluation.
Your doctor will talk to you about your symptoms and when they first began. He or she may ask you whether you can remember any injury to the joint.
During the physical examination, your doctor will have you move your leg in different directions to assess your range of motion and try to replicate the pain. Most patients with transient osteoporosis of the hip have more pain when they move the hip themselves (active range of motion) as opposed to when the doctor moves the hip for them (passive range of motion). In addition, pain is often felt only with extremes of hip movements, and it usually worsens with any weight bearing. This discrepancy (severe pain with weight bearing, but minimal pain with passive range of motion) is one of the clues to the diagnosis of transient osteoporosis.
If you are pregnant, your doctor may decide to delay imaging studies until the last stages of your pregnancy, or even until after the delivery. Generally, MRI is safe to obtain in pregnancy, although you should discuss this with your orthopaedic surgeon, your primary doctor, and your obstetrician if you are considering this test.
One of the most common signs of transient osteoporosis of the hip is bone marrow edema. Bone marrow is a spongy substance that produces blood cells and is located in the hollow of long bones. In bone marrow edema, the bone marrow is inflamed and full of fluid.
An MRI scan of a hip affected by transient osteoporosis will usually reveal bone marrow edema. Because of this, MRI is one of the most useful studies to help diagnose the condition.
Because transient osteoporosis resolves on its own, treatment focuses on minimizing symptoms and preventing any damage to the bones while they are weakened by the disorder.
With proper diagnosis and treatment, most patients with transient osteoporosis of the hip can expect complete resolution of symptoms within 6 to 12 months. Bone strength in the hip also will return to normal in the majority of cases.
In a small percentage of patients, transient osteoporosis recurs later in life. It can return to the same hip or even in the opposite hip. Whether the condition will recur is difficult to predict.