Joint mobility and motor development.
The association of joint hypermobility and motor development was sequentially investigated in 715 infants from the ages of 8 to 14 months. Seven joints were evaluated for mobility, and each infant underwent a physical and neurological examination. Parents were given a Denver Developmental Parents' Questionnaire. All subjects with a general developmental delay, systemic illness or syndrome were excluded. The infants were classified as having normal or delayed motor development with normal or delayed joint mobility. They were re-examined six months later. Multivariate statistical techniques was used for categorical analysis, and three joints were found to be significantly associated with motor delay at the first examination--hip abduction, elbow hyperextension, and foot dorsiflexion. Of the 715 infants, 126 had joint hypermobility and of these 38 (30.2%) had motor delay. Sixty four of 589 (10.9%) with normal joints had delayed motor development. Six months later 23 out of 35 of the group with joint hypermobility and 42 out of 53 of the group with normal joints had normal motor function. Joint hypermobility is associated with an increased incidence of motor delay in infancy. Over the ensuing six months most of the subjects will catch up. These findings, indicating a favourable prognosis, have implications regarding clinical assessment and parental counselling.