Using quantitative imaging methods to investigate the association between quadriceps stiffness and knee cartilage volumes.

AIMS: Sex- and compartment-specific associations between quadriceps weakness and knee cartilage loss have been reported, and stiffer quadriceps has been related to clinical knee symptoms. Nevertheless, the relationship between quadriceps stiffness and knee cartilage health remains unclear. The primary aim of this study was to investigate the association between quadriceps stiffness and knee cartilage volumes.

METHODS

This study included 82 older adults (46 females (56.1%); mean age 65.9 years (SD 3.9)). Passive stiffness of three superficial quadriceps muscle heads was evaluated by using shear-wave elastography ultrasound. Quadriceps strength was measured by a Cybex dynamometer. Cartilage volumes of the tibia, femur, and patella were quantitatively assessed using MRI. Linear regressions were used to examine relationships of quadriceps stiffness and strength with cartilage volumes across different knee compartments, while controlling for potential covariates. Benjamini-Hochberg false discovery rate (FDR) correction was applied to account for multiple tests. Sex-specific relationships were evaluated when significant sex and quadriceps interactions were detected.

RESULTS

Negative associations were observed between quadriceps stiffness and cartilage volumes of tibia (estimate -33.7 mm3/kPa (95% CI -63.2 to -4.2), p = 0.026), femur (-72.4 mm3/kPa (95% CI -128.8 to -16.0), p = 0.013), and total knee (-92.0 mm3/kPa (95% CI -183.2 to -0.7), p = 0.048). However, those associations became statistically non-significant after FDR corrections (FDR-corrected p = 0.104 to 0.128). Quadriceps strength was not associated with cartilage volumes in the full cohort, while a significant sex and strength interaction was observed for patellar cartilage. Sex-stratified analyses showed a positive association between quadriceps strength and patellar cartilage in females (558.2 mm3/Nm*kg-1 (95% CI 126.1 to 990.3), p = 0.013), but not males.

CONCLUSION

Lower quadriceps strength is associated with smaller patellar cartilage volumes in females. Although there is a trend showing negative associations between quadriceps stiffness and tibiofemoral cartilage, there is insufficient evidence in the current sample supporting an affirmative conclusion. Future research is needed to confirm these preliminary findings, and to clarify potential causal effects and clinical implications.