Arthritis and Benign Hypermobility Joint Syndrome
Benign hypermobility joint syndrome -- or BHJS -- is a common source of joint or muscle complaints by children and young adults. Benign hypermobility describes looseness of joints that may be associated with daytime pain, nighttime awakening, or discomfort after exercise. People with the condition generally report prolonged pain. In the past, this type of general pain often was called "growing pains" or "limb pain," which can be similar. Both, though, are different disorders. The term "benign" has been used to differentiate the BHJS from other similar disorders that also involve other organs such as the eyes and heart.
What Are the Symptoms of Benign Hypermobility Joint Syndrome?
Children or young adults with hypermobility usually have joint pain and occasionally mild swelling during the late afternoon, at night, or after exercise or activity. The pain is more common in the lower extremities, such as the calf or thigh muscles. It most often involves large joints such as the knees or elbows, but can involve any joint.
Swelling usually is not present, but when found is due to normal, activity-related trauma to the joints. Signs of inflammation, such as redness and heat, are usually absent. Swelling may come and go within hours.
Who Is Affected by Benign Hypermobility Joint Syndrome?
The frequency of BHJS varies with sex, age, and ethnic background. Girls tend to have more mobility (looseness) of the joints than do boys of the same age. Younger children tend to report more pain. Teenagers may have fewer symptoms because their muscles and joints tend to become tighter and stronger as they become older and because they better understand the relationship between increased activity and discomfort.
BHJS seems to occur more often in Asian-American children than in Caucasian children, and it is least common in African-American children.
When large groups of school children are tested, BHJS is found in as many as 40% of them. About 10% of these children have hypermobility that can lead to pain after activities or at night. No one knows why some children develop discomfort, while others with equally loose joints do not have pain or swelling.
There is often a family history of loose-jointedness. Occasionally there may be a family member with a history of hip dislocations at birth; scoliosis (curvature of the spine); elbow, kneecap or shoulder dislocations; or frequent ankle or wrist sprains.
How Is Benign Hypermobility Joint Syndrome Diagnosed?
Assessment of children or young adults suspected of having BHJS does not require special equipment. Testing the range of motion of your child's joints will determine if they are more loose than normal. Several specific mobility tests are used for diagnosing BHJS, 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 his or her palms flat on the floor.
Since the symptoms of hypermobility can sometimes mimic arthritis, laboratory tests may be required to ensure that your child does not have a more serious disorder (such as juvenile arthritis or other inflammatory conditions). Rarely, X-rays may be required.