Use of finger length ratio as a marker for knee osteoarthritis: A case-control study of 2,456 patients

BackgroundIn the human hand, the index and ring finger present a considerable variation in their relative lengths and the ratio of their lengths (2D:4D ratio). This ratio is associated with a variety of behavioral and physiological traits possibly linked to variation in sex hormones levels. Previous studies have revealed inconsistent results while assessing the association of 2D:4D ratio as a risk factor for occurrence of knee osteoarthritis (KOA). This study was designed as a prospective observational study to analyze this association using a better methodology. MethodsPatients were enrolled into KOA group (1396 patients) and non-KOA group (1060 patients) based on ACR criteria for OA knee. Knee and hand radiographs of all patients enrolled were assessed. The 2D:4D length ratio was calculated for phalanges, metacarpal bones and for the combined (metacarpal & phalanx) finger lengths on radiographs and visual finger lengths. The finger patterns were classified and assessment was done between these ratios and finger pattern types for occurrence and severity of KOA. ResultsA lower 2D:4D ratio in an individual was associated with an increased chance of KOA and a dose response relationship was found between radiographic grading of KOA and 2D:4D ratio. ConclusionBased on the findings of this study one can predict the risk of developing KOA using this simple technique which can be used as a screening tool whereby preventive intervention can be started if someone presents early with a low 2D:4D finger length ratio. KEY MESSAGESO_LIEvaluation of finger patterns reveals an association with osteoartritis knee (KOA) C_LIO_LILow 2D:4D ratio and Type 3 finger pattern is associated with increased KOA risk C_LIO_LILow 2D:4D ratio has as positive correlation to radiographic severity of KOA C_LIO_LIPreventive interventons can be initiated for those with at risk finger pattern C_LI