A study to assess the clinical importance of asymmetric thigh creases as the sole clinical sign in the diagnosis of developmental dysplasia of the hip. METHOD. All consultant clinic letters have been saved on a hospital hard drive since 1999. This drive was searched for the terms “thigh crease” and “skin crease”. Irrelevant letters and referral letters describing factors that would indicate screening in our unit were excluded leaving those with the sole referral complaint of asymmetric thigh creases (ATC). We also reviewed the original referrals of developmental dysplasia of the hip (DDH) patients managed by open or closed reduction. These patients were identified through operative coding. All available hard copy notes were reviewed and patients with neuromuscular conditions or longitudinal deficiency were excluded. Results were inputted into an Excel spreadsheet and analysed by a statistician at the University of Sheffield assuming a background population incidence for DDH of 1 in 1000. RESULTS. 399 computer files containing the search terms were identified. Many contained whole clinics of patient letters. After exclusions we identified 229 patients with the sole referral complaint of ATC. Three of the 229 patients had DDH, which was not statistically significant (p=0.107). The majority of the normal patients had radiological investigations. Hard copy notes were available and relevant for 130 of the 289 operatively managed patients, of whom one was initially referred with the sole complaint of ATC. Orthopaedic specialist examination demonstrated all four patients initially referred with only ATC had decreased abduction and shortening. CONCLUSION. We suggest if the primary health care professional is not confident to exclude DDH in the patient with ATC there is justification for referral, but in the absence of other clinical features or risk factors in the orthopaedic consultation there is no need for further investigation or follow up