Age changes in the flexibility of Down's syndrome children.

The association between Down's syndrome (DS) and joint hyperflexibility is well documented. However, objective information concerning developmental expectations for flexibility in DS children is lacking. This investigation used goniometric techniques to examine the changes in flexibility with growth and maturation in 30 DS children aged 5, 10 and 15 years and compared them with 30 normal controls. Flexibility declined consistently with age in the DS children and in the controls, and although the DS children were more flexible than their control counterparts at each age, the magnitude of change over the whole age range was parallel in both groups of children suggesting some similarity in mechanisms controlling the maturation of joint tissues. The greatest reduction in flexibility occurred in the hip and ankle joints, and in the elbow and knee hyperextension. A trend was evident for the largest reduction in measurements to occur between 5 and 10 years in the DS children compared with a consistent or later reduction in the controls. It is postulated that this may be attributable to the improvement in generalized muscular hypotonia expected during this age period, or to differences in the rate of maturation of joint structures in the early years, caused by the effects of the syndrome on the intrinsic mechanisms regulating the growth of joints.