Hypermobility: features and differential incidence between the sexes.

Six hundred sixty individuals from a music school were studied to determine the frequency of incidence and the nature of their hypermobility. They were interviewed and examined for the 5 recognized features of hypermobility (laxity of the thumbs, fingers, elbows, spine, and knees). The incidence of hypermobility, according to the number of joints involved, followed an empiric geometric law. Approximately 27% of the individuals had 1 lax joint, whereas only 3% possessed all 5 features. Specific features were present at different frequencies in the 2 sexes. The ratio of the occurrence of 2 features in women compared with the occurrence in men was 2:1. Ratios for the occurrence of 3, 4, and 5 features were 4:1, 8:1, and 3:1, respectively. Thus, hypermobility was a predominantly female characteristic. Joint laxity declined with age, although not to a statistically significant degree. In men, the decline started when they were in their mid-twenties; however, in women, joint laxity continued through the mid-forties.