Osteoarthritis Risk Linked to Finger Length Ratio

Researchers at the University of Nottingham (United Kingdom) conducted a case-control study to assess the relationship between the index to ring finger length ratio (referred to as 2D:4D), and the risk of knee and hip OA. 2,049 case subjects were recruited from hospital orthopedic surgery lists and a rheumatology clinic in Nottingham. All had clinically significant symptomatic OA of the knees or hips, requiring consideration of joint replacement surgery. Another 1,123 individuals with no radiographic evidence of hip or knee OA, no present hip or knee symptoms, and no history of joint disease or joint surgery served as a control group. Radiographs of both knees and the pelvis were obtained for all participants. Every participant also underwent separate radiographs of the right and left hands. Researchers then assessed the 2D:4D length ratio from radiographs using three methods: a direct visual comparison of the two finger ends, the measured ratio from the base to the tip of the upper finger joints, and the measured ratio of the metacarpal bone lengths.

The findings suggest that having a relatively long ring finger to index finger ratio raises the risk for developing OA of the knee, independent of other risk factors and particularly among women. Among participants of both sexes, researchers also found an interesting trend: the smaller the 2D:4D upper finger joint ratio, the greater the risk of OA of the tibiofemoral knee joint. Finally, after adjusting for the established OA risk factors including age, sex, body mass index, joint injury, and lack of physical activity, the strong association of smaller 2D:4D length ratio with the risk for knee OA was deemed independent of these factors. The study was published in December 2007 edition of the journal Arthritis and Rheumatism.

"The 2D:4D length ratio appears to be a new risk factor for the development of OA. Specifically, women with the ‘male' pattern of 2D:4D length ratio that is, ring finger relatively longer than the index finger are more likely to develop knee OA,” said lead author Professor Michael Doherty.

Index to ring finger length ratio is a trait known for its differences between the sexes. Men typically have shorter second than fourth digits; in women, these fingers tend to be about equal in length. Smaller 2D:4D ratios have been shown to hold hormonal connections, including higher prenatal testosterone levels, lower estrogen concentrations, and higher sperm counts.


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