The Effect of Knee Arthritis on Energy Consumption

A number of interrelated factors are present in osteoarthrosis of the knee joint that have an effect on energy consumption.

A tendency to flexion relative to normal at the knee and the hip in mid stance is associated with increased external flexing moments. Knee flexion contracture is a common finding in UK patients prior to surgery but in the Boston patients studied by McGibbon et al (2002) with osteoarthrosis of the knee alone the knees hyper extended relative to normal in mid stance. Clearly the stage of disease will lead to a variability in the changes seen and the impact on efficiency. The reaction to early arthritic change may be explained by a desire to minimise moments about the knee.

In McGibbons study, diminished biomechanical power generation at the knee and ankle is compensated for by a relative increase in power generated at the hip and lumbar spine. Exactly why one of the main motors for propulsion is suppressed is not yet clear however the action of gastrocnemius in terminal stance is to drive the knee into flexion and to do so by acting across the knee joint thus potentially increasing contact force. If on the other hand the hip is used to generate the power to accelerate the knee into flexion it can be done without increasing the contact pressure so dramatically. McGibbons et al suggest that a lack of a second peak of distally directed power in the knee at terminal stance explains the lack of ankle power generation but the contact pressure explanation was not discussed. The low second peak of knee power generation was ascribed to the lack of vigorous quadriceps action.

from McGibbons et al

References

McGibbon CA, Krebs DE. Compensatory gait mechanics in patients with unilateral knee arthritis. J Rheumatol 2002;29(11):2410-9.

Waters RL, Barnes G, Husserl T, Silver L, Liss R. Comparable energy expenditure after arthrodesis of the hip and ankle. J Bone Joint Surg Am 1988;70(7):1032-7.

Stauffer RN, Chao EY, Gyory AN. Biomechanical analysis of the diseased knee joint. Clin Orthop 1977;126:246-255.