The associations between finger length pattern, osteoarthritis, and knee injury: data from the Framingham community cohort

Objective: To investigate the associations of index finger-to-ring finger (2D:4D) length ratio with radiographic knee and hand osteoarthritis (OA), previous knee injury, and meniscal lesions in the general population.

Methods: We measured the length of the right second and fourth phalangeal and metacarpal bones on hand radiographs from 1,020 randomly recruited subjects (ages 51-92 years). Knee radiography and magnetic resonance imaging (MRI) were performed on subjects. Women and men were divided into tertiles according to their 2D:4D phalangeal and metacarpal ratios. We assessed the odds ratios (ORs) and 95% confidence intervals (95% CIs) for radiographic knee OA, severe symptomatic knee OA, radiographic hand OA, previous knee injury, and MRI-defined meniscal lesion, using logistic regression with adjustment for age and body mass index. Because hand OA may affect the 2D:4D phalangeal ratio, we performed sensitivity analyses in subjects without joint space narrowing in the second and fourth interphalangeal joints.

Results: We found no significant associations between 2D:4D length ratio and radiographic knee OA, severe symptomatic knee OA, or meniscal lesions. Low 2D:4D phalangeal ratio was associated with hand OA in women (OR 1.80, 95% CI 1.11-2.93), but in the sensitivity analysis, the association was attenuated (OR 1.35, 95% CI 0.79-2.32). Low 2D:4D phalangeal ratios were associated with knee injury in men (OR 1.78, 95% CI 1.02-3.10). We found no significant associations for 2D:4D metacarpal ratios.

Conclusion: Low 2D:4D phalangeal ratios in men are associated with knee injury, but we did not find any significant association with knee OA. Low 2D:4D length ratio may be a consequence, rather than a cause, of hand OA in women.