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    What Is Benign Hypermobility Joint Syndrome?

    Benign hypermobility joint syndrome (BHJS) means your joints are “looser” than normal. It’s a common joint or muscle problem in children and young adults.

    The condition can cause pain or discomfort after exercise. It’s not part of any disease.

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    Children or young adults with hypermobility usually have joint pain.

    The pain is more common in the legs, such as the calf or thigh muscles. It most often involves large joints such as the knees or elbows. But it can involve any joint.

    Some people also have mild swelling in the affected joints, especially during the late afternoon, at night, or after exercise or activity. That swelling may come and go within hours.

    Who Gets It?

    Girls’ joints tend to be more mobile (looser) than those in boys of the same age. Younger children tend to report more pain. Teens may have fewer symptoms because their muscles and joints become tighter and stronger as they get older.

    BHJS seems to happen more often in Asian-American children than in Caucasian children, and it is least common in African-American children. The reasons for that aren’t clear.

    When large groups of schoolchildren are tested, as many as 40% have the syndrome. About 10% of these children have hypermobility that can lead to pain after activities or at night. No one knows why some children feel that discomfort, while others with equally loose joints don’t have pain or swelling.

    Loose joints often run in families.


    Simple tests show whether a child has a greater range of motion in their joints than normal. Doctors use several specific mobility tests, including:

    • The wrist and thumb can be moved downward so the thumb touches the forearm.
    • The little fingers can be extended back beyond 90 degrees.
    • When standing, the knees are abnormally bowed backward when viewed from the side.
    • When fully extended, the arms bend further than normal (beyond straight).
    • When bending at the waist, with the knees straight, the child or adult can put their palms flat on the floor.

    Since the symptoms of hypermobility can sometimes mimic arthritis, you may need to get lab tests to make sure your child doesn’t have a more serious disorder (such as juvenile arthritis or other inflammatory conditions). In rare cases, you may need to get X-rays.

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