Flat Feet Are Associated With Knee Pain and Cartilage Damage in Older Adults

Researchers assessed the cross-sectional relation of planus foot morphology to ipsilateral knee pain and compartment-specific knee cartilage damage in older adults. The study, of 1,900 adults in their 50s or older, found that those with the flattest feet were 31 percent more likely than other study participants to say they had knee pain on most days. And they were 43 percent more likely to show damage to the cartilage at the inside of the knee.


Dr. Gordon has always believed that bad knees can be caused or exacerbated by flat feet. In 1994 he was talking about a research project with the Chairperson of the Department of Orthopedics at the University of Washington to see if a well made orthotic device would prevent knee surgeries specifically joint replacement surgery. Regrettably he left Seattle before the project could get off the ground.

Abstract

Objective.

To assess the cross-sectional relation of planus foot morphology to ipsilateral knee pain and compartment-specific knee cartilage damage in older adults.

Methods.

In the Framingham Studies, we adapted the Staheli Arch Index (SAI) to quantify standing foot morphology from pedobarographic recordings. We inquired about knee pain and read 1.5 Tesla MRIs using whole-organ magnetic resonance imaging scoring. Logistic regression compared the odds of knee pain among the most planus feet to the odds among all other feet, and estimated odds within categories of increasing SAI. Similar methods estimated the odds of cartilage damage in each knee compartment. Generalized estimating equations adjusted for age, sex, BMI, and non-independent observations.

Results.

Among 1903 participants (mean age 65± 9 years; 56% female), 22% of knees were painful most days. Cartilage damage was identified in 45% of medial TF, 27% of lateral TF, 58% of medial PF, and 42% of lateral PF compartments. Compared with other feet, the most planus feet had 1.3 (95% CI: 1.1, 1.6) times the odds of knee pain (p=0.009), and 1.4 (95% CI: 1.1, 1.8) times the odds of medial TF cartilage damage (p=0.002). Odds of pain (p_trend=0.05) and medial TF cartilage damage (p_trend=0.001) increased linearly across categories of increasing SAI. There was no association between foot morphology and cartilage damage in other knee compartments.

Conclusion.

Planus foot morphology is associated with frequent knee pain and medial TF cartilage damage in older adults.