The effect of mild to moderate knee osteoarthritis on gait and three-dimensional biomechanical alterations

Key points

1. 01Grade II KOA patients had a significantly prolonged gait cycle (1.14 s vs 1.09 s in controls) and increased step width (0.10 m vs 0.07 m in controls).
2. 02Grade II patients showed a shortened swing phase on the affected side (39.53% vs 41.19% in controls, p=0.01).
3. 03Hip and knee range of motion was reduced even at grade I, with further reductions at grade II across multiple planes.
4. 04Grade I patients showed an elevated knee abduction moment compared to controls, a pattern that reversed and decreased markedly in grade II.
5. 05Ankle joint moments did not differ significantly between groups, though a downward trend in ankle flexion moment was observed with increasing severity.

How it was conducted

Design

Case-control study with three groups: healthy controls, K-L grade I KOA patients, and K-L grade II KOA patients

Participants

Total of 48 participants (16 per group); adults aged between unspecified range, recruited from a sports rehabilitation center

Grading

Kellgren-Lawrence grading scale used to classify KOA severity; unilateral mild KOA (grade I or II) required for inclusion

Gait measurement

Vicon Nexus 10-camera infrared motion capture system and two AMTI OR6-7 force plates; data normalized and processed in Visual 3D software

Primary outcomes

Gait parameters (cycle time, step width, swing/stance phase), joint ROM in three planes, maximum angular velocity, and joint peak moments (extension, flexion, abduction, adduction, rotation) at hip, knee, and ankle

Statistical analysis

One-way ANOVA with post hoc Bonferroni correction; significance set at p<0.05; effect sizes (Cohen's d) reported

What they found

• Gait cycle time: controls 1.09 +/- 0.07 s, grade I 1.10 +/- 0.14 s, grade II 1.14 +/- 0.12 s; control vs grade II p=0.01 (Cohen's d=0.83); grade I vs grade II p=0.01 (Cohen's d=0.81).
• Step width: controls 0.07 +/- 0.03 m, grade I 0.08 +/- 0.02 m, grade II 0.10 +/- 0.03 m; control vs grade II p=0.01 (d=1.75); grade I vs grade II p=0.01 (d=1.31).
• Affected swing time: controls 41.19 +/- 2.51%, grade II 39.53 +/- 3.86%; control vs grade II p=0.01 (d=0.81); grade I vs grade II p=0.02 (d=0.60).
• Knee sagittal ROM: controls 65.06 +/- 2.84 deg, grade I 61.92 +/- 5.40 deg, grade II 61.07 +/- 4.77 deg; control vs grade I p=0.01 (d=0.95); control vs grade II p=0.01 (d=1.16).
• Ankle sagittal ROM: controls 59.08 +/- 6.53 deg, grade I 55.60 +/- 9.00 deg, grade II 50.85 +/- 5.93 deg; control vs grade I p=0.01 (d=0.66); control vs grade II p=0.01 (d=1.49); grade I vs grade II p=0.01 (d=0.97).
• Hip horizontal plane ROM: controls 14.44 +/- 4.65 deg, grade I 11.06 +/- 3.08 deg, grade II 12.69 +/- 3.31 deg; control vs grade I p=0.01 (d=1.31); control vs grade II p=0.01 (d=0.69); grade I vs grade II p=0.02 (d=0.65).
• Maximum knee angular velocity (sagittal): controls 398.06 +/- 71.49 deg/s, grade II 362.78 +/- 61.70 deg/s; control vs grade II p=0.01 (d=0.78).
• Hip peak extension moment was significantly lower in grade I compared to controls, and further reduced in grade II (p<0.05 for both).
• Hip peak flexion moment was significantly lower in grade II compared to both controls and grade I (p<0.01).
• Knee peak extension moment was significantly reduced in grade I vs controls; knee peak flexion moment was further decreased in grade II vs both controls and grade I.
• Knee peak abduction moment was significantly higher in grade I vs controls, but markedly reduced in grade II.
• No significant differences in ankle joint moments were found among the three groups.

Limitations

• Trunk and contralateral limb compensatory strategies were not analyzed, which may underestimate whole-body gait adaptations.
• Marker-based motion capture is susceptible to soft tissue artifacts, potentially affecting kinematic measurement accuracy.
• Laboratory gait assessments may not reflect natural real-world walking patterns.
• No diagnostic thresholds or predictive models were established, limiting direct clinical translation.

Why it matters

For patients

People with early knee osteoarthritis may already have altered walking mechanics that increase joint stress, making early physiotherapy assessment worthwhile even when symptoms feel mild.

For clinicians

Grade-specific biomechanical profiles (elevated knee adduction moment at grade I, reduced moments and ROM at grade II) can guide targeted gait retraining, bracing, and assistive device prescription at each disease stage.

For readers

This study quantifies how 3D gait biomechanics degrade from grade I to grade II knee OA, providing a baseline for future longitudinal and AI-driven screening research.