THE INFLUENCE OF PERCENTAGE BODY WEIGHT SUPPORT AND CRUTCH WALKING TECHNIQUE ON THE REDUCTION OF KNEE JOINT CONTACT FORCES

M. Hagen¹, T. Leppens¹, D. Van Assche¹, S. Verschueren¹, J. Vanrenterghem¹

¹KU Leuven, Department of Rehabilitation Sciences, Leuven, Belgium

Background: Acute knee cartilage injuries occur regularly in young individuals(Gage et al., 2012). These injuries typically require protection and load reduction in the early phases of rehabilitation, which is managed with crutches(Dubois & Esculier, 2020). The desired knee loading is usually prescribed indirectly as a percentage of the total body weight (BW). However, these prescriptions do not consider compressive forces generated by muscles crossing the knee joint. Furthermore, earlier studies on knee joint loading during crutch walking have reported knee joint moments and not knee joint contact forces (KJCF)(Rasouli & Reed, 2020).

Purpose: The purpose of this study was to investigate the influence of percentage BW support and crutch walking technique on the reduction of KJCF during walking with elbow crutches.

Methods: In order to make the conclusions of the study generalisable to a wide range of knee pathologies, five healthy men and five healthy women (age=23±1years, weight=67.9±16.0kg, length=176.6±11.6cm) were included in this study. The following crutch walking techniques were examined: 3-point gait with bilateral crutch use (BI), 2-point gait with unilateral crutch use on the ipsilateral side (UI) and 2-point gait with unilateral crutch use on the contralateral side (UC). The BI walk was performed at 25, 50 and 75%BW, the UI and UC walk were only performed at 50 and 75%BW. Walking without crutches was also measured as control condition. Motion capture data (100HZ; Vicon, Oxford, UK), ground reaction force data (1000Hz; AMTI, Watertown, USA) and electromyography data (1000Hz; Cometa Mini Wave, Milan, Italy) were collected. KJCF were calculated in OpenSim (Stanford, USA) using an electromyography-constraint approach. The main effect of percentage BW support was statistically analysed with a one-way repeated measures ANOVA on the BI conditions. The main effect of walking technique and interaction effect of percentage BW support and walking technique was investigated with a two-way repeated measures ANOVA on the BI, UI and UC walks at 50% and 75%BW.

Results: The relative reduction in KJCF was always smaller than the prescribed reduction in percentage BW support. A significant main effect was found for percentage BW support during BI walking (p<0.001) with KJCF increasing steadily from 25% (2.64±0.72BW) to 75% (3.15±0.68BW). The two-way ANOVA on the different walking techniques at 50% and 75%BW found both a main effect for walking technique (p<0.001) and an interaction effect between percentage BW support and walking technique (p=0.020). Both unilateral walking techniques had higher KJCF than BI and sometimes even higher than normal walking (3.70±0.75BW). At 50%BW, the values for the UC condition were higher (3.83±0.82BW), while at 75%BW the KJCF were larger in the UI condition (3.94±0.07BW).

Conclusions: When prescribing crutches to unload the knee cartilage, two crutches have to be used to reduce KJCF. The use of one crutch cannot reduce KJCF sufficiently, not even when supporting only 50%BW on the leg.

Implications: Compressive muscle forces have to be considered when prescribing load reduction programs in the early rehabilitation after knee injuries. These can only be reduced through bilateral crutch use.

Funding acknowledgements: PhD Fellowship fundamental research FWO Flanders

Keywords:
Load management
Musculoskeletal biomechanics
Knee cartilage

Topics:
Musculoskeletal: lower limb
Primary health care
Disability & rehabilitation

Did this work require ethics approval? Yes

Institution: KU Leuven

Committee: Ethics Committee Research UZ/KU Leuven

Ethics number: S62706