Historically, this has been a controversial issue, with the American Academy of Pediatrics recommending screening and another prominent group, the United States Preventive Services Task Force, recommending against it, arguing that the evidence has been insufficient.

But a study published in July by researchers at Children’s Hospital Boston may settle things. The study recommends giving every newborn a simple physical exam, which takes about one minute, followed by ultrasound if the exam raises red flags.

The study, led by Dr. Susan T. Mahan, a pediatric orthopedic surgeon at Children’s, analyzed data from more than 70 studies dating back to 1939. It compared screening with physical exam and ultrasound, to physical exam plus ultrasound only if warranted, to no screening at all. Physical exam plus ultrasound, when warranted, proved best at picking up hip dysplasia.

Hip dysplasia, which means the baby’s hip joint is too shallow or unstable, can lead to early arthritis and lifelong pain. Hip dysplasia is the most common congenital defect in newborns, though estimates of incidence vary widely – from 1.4 per 1,000 babies to more than 35 per 1,000, depending on the age of the baby studied and the method used for detection. It is also the most common cause of osteoarthritis of the hip in North America, Europe, and Japan. The risk increases if there is a family history of the problem and if the birth is breech (the baby’s bottom delivers first).

“If you were to ultrasound all newborn hips within the first week or so of birth, as many as 20 percent may have some abnormality,” says Mahan, though 90 percent of these get better on their own. Treatment typically involves placing the child in a soft harness for six weeks or so to straighten the hips; in more severe cases, a cast or surgery may be necessary.

The goal, says Mahan, is to use screening to catch the cases that probably would not get better on their own and intervene early.