The relationship of peak ankle dorsiflexion angle with lower extremity biomechanics

Key points

1. 01Peak ankle dorsiflexion during stance correlated with 10 biomechanical variables across the ankle, knee, hip, pelvis, and ground reaction forces
2. 02Lower dorsiflexion was associated with increased knee external rotation (r = -0.394) and hip adduction (r = -0.256), suggesting compensatory transverse and frontal plane movement
3. 03Higher dorsiflexion was associated with greater ankle plantarflexion moment (r = 0.432), hip flexion moment (r = 0.341), and anterior ground reaction force (r = 0.543)
4. 04A data-driven cutoff of 9.03 degrees was established as the threshold for functional limited ankle dorsiflexion during walking
5. 05These biomechanical changes may contribute to patellofemoral pain, iliotibial band syndrome, hip osteoarthritis, and low back pain

How it was conducted

Design

Cross-sectional correlation study

Participants

70 healthy adults (63 male, 7 female); mean age 28.99 years, mean height 172.81 cm, mean mass 73.10 kg

Data collection

8-camera Vicon motion capture at 100 Hz with two AMTI force plates at 1000 Hz during self-selected walking speed

Primary analysis

Spearman correlation between peak ankle dorsiflexion angle and 23 biomechanical variables at that moment, followed by factor analysis and cutoff analysis using maximally selected Wilcoxon statistic

Primary outcome

Correlation coefficients and a statistically derived cutoff angle for functional limited ankle dorsiflexion

What they found

• Peak ankle dorsiflexion positively correlated with ankle plantarflexion moment (r = 0.432; p = 0.001), ankle external rotation moment (r = 0.251; p = 0.036), hip extension angle (r = 0.281; p = 0.018), hip flexion moment (r = 0.341; p = 0.004), pelvic ipsilateral rotation (r = 0.284; p = 0.017), medial ground reaction force (r = 0.324; p = 0.006), anterior ground reaction force (r = 0.543; p = 0.001), and vertical ground reaction force (r = 0.322; p = 0.007)
• Peak ankle dorsiflexion negatively correlated with knee external rotation angle (r = -0.394; p = 0.001) and hip adduction angle (r = -0.256; p = 0.032)
• Factor analysis on the 10 significant variables yielded a single common factor (KMO = 0.728; p < 0.01) explaining 38.37% of data variation; peak ankle dorsiflexion correlated with this factor (r = 0.525; p < 0.01)
• The maximally selected Wilcoxon statistic identified a cutoff of 9.03 degrees; participants below this threshold showed significantly different lower limb movement patterns
• Median peak ankle dorsiflexion in the sample was 9.47 degrees (IQR 5.83)

Limitations

• The sample was predominantly male (63 of 70), so findings may not generalise to women
• Results apply only to level walking; effects of limited dorsiflexion on running, stair negotiation, or other tasks were not assessed
• All participants were healthy young adults (mean age 29 years), limiting applicability to clinical or older populations
• Cross-sectional design cannot establish whether limited dorsiflexion causes the observed biomechanical changes or vice versa

Why it matters

For patients

People with stiff ankles during walking may unknowingly be placing extra stress on their knees, hips, and lower back as compensating joints, which could contribute to pain over time.

For clinicians

A peak ankle dorsiflexion angle below 9.03 degrees during gait identifies functional limitation and warrants targeted rehabilitation to address downstream kinetic chain compensation.

For readers

This study provides a gait-derived, biomechanically grounded threshold for functional ankle dorsiflexion limitation, complementing passive range-of-motion tests already used in clinical practice.