Foot Shape Changes During Pregnancy and Postpartum Are Associated With Patient Pain and Function

Clin Orthop Relat Res. 2026 Jul 10. doi: 10.1097/CORR.0000000000004061. Online ahead of print.

ABSTRACT

BACKGROUND: Foot pain and symptoms affect 42% of pregnant women and extend beyond gestation, but the associations between foot morphology and these symptoms are not well understood. We sought to identify changes in foot shape throughout pregnancy and postpartum, using a novel multiplane digital camera-based system and to determine whether these alterations are associated with clinically important changes in the Patient-Reported Outcomes Measurement Information System (PROMIS) Pain Interference and Physical Function scores.

QUESTIONS/PURPOSES: (1) How does foot width, length, dorsum height, Arch Height Index, and medial foot area change throughout pregnancy and postpartum? (2) Are there relationships between foot shape and changes in foot shape over time with clinically important changes in PROMIS Pain Interference and Physical Function scores during pregnancy and postpartum?

METHODS: Between December 2023 and November 2024, we recruited patients scheduled for an obstetrics visit at Penn Medicine clinics in the Philadelphia, PA, USA, area who were between the gestational ages of 6 to 15 weeks, older than 18 years of age, had a BMI less than 45, had no history of connective tissue disorders or trauma to the lower extremities, and could understand and provide written consent. Of 2067 contacted patients, 40 consented and scheduled a laboratory visit; 78% (31 of 40) had complete datasets and were available for analysis. Pregnant participants (mean ± SD age of 35 ± 4 years, mean ± SD BMI of 68.8 ± 11.8 kg) visited the laboratory between 9 and 15 weeks (early pregnancy), 23 and 27 weeks (mid-pregnancy), and 34 and 39 weeks (late pregnancy) of gestation as well as between 9 and 15 weeks postpartum for foot shape assessment and completion of PROMIS scores. We developed a multiplane digital imaging approach designed to capture the top and medial views of the foot simultaneously to allow rapid quantification of foot shape while eliminating exposure to ionizing radiation. We validated this system by longitudinally monitoring foot shape in a control group of 18 nonpregnant participants (mean ± SD age of 28 ± 4 years, mean ± SD BMI of 62.7 ± 6.4 kg) assessed 12 weeks apart. This control group included female patients who had no previous pregnancies, were older than 18 years of age, had a BMI less than 45, had no history of connective tissue disorders or trauma to the lower extremities that resulted in medical intervention, and could provide written consent. We collected PROMIS Pain Interference and Physical Function score assessments during pregnancy and postpartum. Both scores are standardized T-scores and range from 20 to 80, with higher Pain Interference and lower Physical Function scores indicating worse outcomes. Minimum clinically important differences for pain interference and physical function in foot and ankle orthopaedics range between 5.5 and 9.8 T-score points; therefore, we used a conservative threshold of > 10, which represents 1 SD, to identify clinically important changes in pain interference and physical function during pregnancy.

RESULTS: We found that foot shape changed from early to late pregnancy, with median (range) increases in left foot width (9.14 cm [8.42 to 11.50] versus 9.30 cm [8.55 to 10.57], median difference +0.21 cm [95% CI 0.06 to 0.25]; p = 0.02), left dorsum height (6.22 cm [5.52 to 7.12] versus 6.33 cm [5.67 to 7.78], median difference +0.17 cm [95% CI 0.01 to 0.46]; p = 0.03), and right dorsum height (6.30 cm [5.51 to 7.58] versus 6.50 cm [5.52 to 7.64], median difference +0.23 cm [95% CI 0.13 to 0.38]; p = 0.008). There were mean ± SD increases in left foot length (24.37 ± 1.24 cm versus 24.66 ± 1.12 cm, mean difference +0.29 cm [95% CI 0.09 to 0.49]; p = 0.03), left medial foot area (83.08 ± 7.12 cm2 versus 87.30 ± 7.15 cm2, mean difference +4.22 cm2 [95% CI 2.19 to 6.25]; p = 0.001), and right medial foot area (84.02 ± 7.71 cm2 versus 88.10 ± 8.53 cm2, mean difference +4.08 cm2 [95% CI 2.21 to 5.94]; p < 0.001). In addition, median (range) left foot width increased from early pregnancy to the postpartum period (9.14 cm [8.42 to 11.50] versus 9.42 cm [8.29 to 10.77], median difference +0.10 cm [95% CI 0.09 to 0.37]; p = 0.01). We found associations between foot shape and patient-reported pain during pregnancy. Pregnant participants with clinically important increases in pain interference from early to late pregnancy had increased right medial foot area during late pregnancy (median [range] 11.37 cm2/shoe size [9.72 to 15.97], median difference +1.02 cm2/shoe size [95% CI 0.42 to 1.73]; p = 0.005) and postpartum (11.26 cm2/shoe size [9.88 to 15.47], median difference +0.91 cm2/shoe size [95% CI 0.04 to 2.57]; p = 0.01) compared to the control group of nonpregnant participants (10.35 cm2/shoe size [8.76 to 11.54]). Pregnant participants with clinically important increases in pain interference from early to late pregnancy also demonstrated an increase in right foot length from early to late pregnancy when compared with nonpregnant participants who had no changes in pain interference (0.49 ± 0.59 cm versus -0.14 ± 0.49 cm, mean difference 0.63 cm [95% CI 0.21 to 1.06]; p = 0.005). Pregnant participants with clinically important declines in physical function had a greater increase in right medial foot area from early to late pregnancy than pregnant participants without a physical function decline (6.62 ± 4.94 cm2 versus 1.98 ± 4.00 cm2, mean difference 4.64 cm2 [95% CI 1.14 to 4.64]; p = 0.01).

CONCLUSION: This study identified potential morphological risk factors for musculoskeletal pain and reduced function in pregnant patients. Patient-reported pain and function were predominantly associated with pregnancy-induced lower extremity edema. These findings have potential clinical impact to guide interventions (such as compression socks, massage, or foot elevation) aimed at managing foot changes during pregnancy to reduce musculoskeletal pain and disability.Level of Evidence Level III, prognostic study.

PMID:42439597 | DOI:10.1097/CORR.0000000000004061