The Effect of Arch Drop on Tibial Rotation and Tibiofemoral Contact Stress in Postpartum Women.
Level 4 - case-series / case-control
Single-group biomechanical interventional study with internal controls.
PubMed 29705172 · doi:10.1016/j.pmrj.2018.04.006
What was done
Eleven postpartum women (mean age 33.4 ± 5.3 years, body mass 76.1 ± 13.5 kg) with pregnancy-related arch drop underwent standing computed tomography (CT) with knees in 20° fixed flexion, with and without semirigid arch supports to simulate prepregnancy arch height. Knee magnetic resonance imaging was acquired at matching flexion. Bone and cartilage segmentations were registered to 3D CT models to computationally measure tibial rotation and estimate medial and lateral tibiofemoral contact stress.
What was found
Arch drop caused a statistically significant mean tibial internal rotation of 0.75 ± 1.33° (P = .02). No statistically significant changes were detected in mean or peak tibiofemoral contact stress.
Why it matters
The findings demonstrate that foot arch collapse after pregnancy induces subtle internal rotation of the tibia, suggesting a biomechanical mechanism that may increase stress on knee soft tissues.
Limits
The sample size was very small (n = 11), making contact stress comparisons vulnerable to type II error. Biomechanics were evaluated in a static 20° fixed-flexion stance rather than dynamic gait, contact stresses were estimated computationally rather than measured directly, and clinical symptoms were not assessed.
Cited by
- supports When the foot arch collapses, the tibia undergoes torque in its relationship to the foot, transmitting ground reaction forces up through the ankle into the knee, hip, and back.