Supple to stiff

In a cross-sectional, multicenter prevalence study, Soucie and colleagues (page 2467) analyzed range-of-motion data on more than 4000 hemophilic male subjects, aged 2 to 19 years. As expected, there was an inverse relationship between flexibility and age. However, teens with more severe phenotypes were less flexible than those at the same age with milder phenotypes. Soucié et al also examined several factors that correlate with less flexible joints at increased ages. These data represent the first analysis of joint motion in the Universal Data Collection set being collected by the Centers for Disease Control (CDC). This is an ambitious project that has enrolled more than 1200 hemophilic subjects from 136 hemophilia treatment centers that are partially supported by funds from the CDC.

The methodology for assessing joint flexibility poses a problem as there are no standardized methods with which to compare the data collected. Although not assessed formally, it is a reasonable assumption that the joint range-of-motion measurements between centers are comparable. Center personnel have had uniform, formal training in the methods, and the majority of measurements were performed by physical therapists during annual assessments. It is unfortunate that there are no normal pediatric control data, so “normal range” is derived from limited data on adults. Furthermore, longitudinal or repeat measurement data were not available to assess variability in the measurements or across time in given subjects. Data presented are largely from a global assessment of all joints measured compared with normal. This limitation was addressed in part by an analysis for asymmetric ranges of motion in the same joint, letting each patient serve as his/her own control. For the latter, a difference of more than 20 degrees seems reasonable to indicate that there is arthritic involvement, although it would be useful to see how the data segregate when other values are selected. It should be noted that subjects with acute limitations from recent bleeding episodes were to be noted and excluded from analysis of those joints. Other limitations are that only treatment patterns, presence of inhibitors, or surgical procedures in the recent past are considered. Thus, an older subject may have had severe complications or limited treatment in the past that could account for at least some of the changes in the lower flexibility noted in the global measurement with increasing age.

Data across time will be important to analyze in future studies; fortunately most of those with severe bleeding tendencies participate on an annual basis. Comparable data on healthy subjects is needed as well. It will be of interest to compare data from young adults, as there is no particular rationale provided for the 19-year-old cutoff. In the future, it will be important to capture more details of prior history to determine its effect on decreasing flexibility as the hemophilic subject grows older.