Hip problems in older adults: classification by cluster analysis.

No validated classification system of hip disorders in primary care is available. This study explores whether it is possible to obtain such a classification with the method of cluster analyses. A total of 224 consecutive patients aged 50 years or older, consulting the general practitioner for pain in the hip region, and referred for X-ray investigation of the hip, underwent a standardized examination. Ward's cluster analysis with variables from history and physical examination of the hip region resulted in a classification with nine different clusters. These clusters were reproduced in 10 random subsamples and with an alternative cluster analysis. Significant relationships of various external variables (radiological and sonographic signs and variables of low-back and knee examination) with the distinctive clusters were found. Twenty of the approached experts recognized the symptoms in seven clusters as identifiable syndromes. However, further validation of the achieved classification system, especially with respect to the clinical importance, is needed before introducing it into clinical practice.