Is there significance to the length of the index finger? Yuanyuan Wang, M.D., from Monash University’s Department of Epidemiology and Preventive Medicine, decided to find out. He put together a study to determine whether the ratio of the lengths of the index and ring fingers was associated with the risk of knee or hip OA severe enough to require joint replacement.

“We assessed the ratio of the lengths of the index finger and ring fingers of middle-aged and older people participating in the long established Melbourne Collaborative Cohort Study using photocopies that were taken of their hands, ” Wang said. “This was compared to the incidence of total knee and hip replacements between 2001 and 2011. We achieved this by linking the cohort records to the Australian Orthopaedic Association National Joint Replacement Registry.”

In the 11 years following the initial finger measurements, doctors reported a total of 580 knee replacements and 499 hip replacements. “This indicates that lower index to ring finger ratio is associated with a higher incidence of total knee replacement, ” Wang said. “The results were consistent when the ratio was examined both on the right and left hand, with the risk being stronger for the right hand.”

Wang’s findings supported the belief that hormonal factors play a role in the origin and development OA, and may possibly account for gender differences in the prevalence of OA. “Although our study’s results may in part be explained by joint injuries associated with high-level physical activity in those with a lower 2D:4D and the greater susceptibility of knee OA in response to injury than hip OA, they may also reflect hormonal influences on the growth of the bone, cartilage and soft tissue, ” Wang said.