Effects of increased chronic loading on articular cartilage material properties in the Lapine tibio-femoral joint

Abstract

Methods of producing relevant and quantifiable load alterations in vivo with which to study loadinduced cartilage degeneration analogous to osteoarthritis are limited. An animal model was used to investigate the effects of increased chronic loads on articular cartilage. Mature rabbits were randomized into one of three experimentally-loaded groups and a fourth unoperated control group. A mechanical-loading device was skeletally fixed to the hind limb of animals in the loaded groups. Engaging the device resulted in an additional load of 0, +22 or +44% body weight to the medial compartment of the experimental knee while allowing normal joint function. Following a 12-week loading protocol, a creep indentation test and needle probe test were used to determine the biphasic material properties and thickness of the cartilage at four locations of each femoral and tibial condyle of the experimental and contralateral limbs. Analyses of covariance were performed to compare outcome measures across treatment groups. The effect of increased load was site and load-level specific with alterations of materialproperties and thickness most prominent in the posterior region of the medial compartment of the tibia. At this site, permeability increased 128% and thickness increased 28% in the +44% body weight group relative to the 0% body weight group. This model of altered chronic loading initiated changes in material properties to the articular cartilage at the sites of increased load over 12-weeks that were consistent with early degenerative changes suggesting that increased tibio-femoral loading may be responsible for the alterations. This work begins to elucidate the chronic load threshold and the time course of cartilage degeneration at different levels of altered loading.

Very early osteoarthritis changes sensitively fluid flow properties of articular cartilage

“…Using isotropic biphasic or FRPE models, published permeability values are similar to those found by us (Julkunen et al, 2009a(Julkunen et al, , 2009bRoemhildt et al, 2006;Roemhildt et al, 2010;Sah et al, 1997). However, using the FRPE-model, Julkunen et al (Julkunen et al, 2009a) reported values for the fibrillar and non-fibrillar matrix moduli that were about 3 times greater than those reported here.…”

“…Earlier, lapine and canine cartilage samples have been shown to have high dynamic stiffness for femoral condyle and groove cartilage (Jurvelin et al, 1987;Rasanen and Messner, 1996;Roemhildt et al, 2006Roemhildt et al, , 2010. We found femoral groove cartilage to have the highest fibrillar stiffness and the lowest permeability.…”

A Novel Experimental Knee-Pain Model Affects Perceived Pain and Movement Biomechanics

“…These biomechanical alterations would also likely affect articular cartilage health, as articular cartilage health depends upon appropriate knee jointloading patterns. 14,37 An unloading strategy might also result in chronic bilateral strength asymmetry 38 because this potential unloading strategy implies altered loading characteristics for the uninvolved lower extremity. For example, if impulse due to vertical GRF is decreased for the involved lower extremity, the same impulse must increase for the uninvolved lower extremity to adequately support the center of mass during walking.…”

“…If such changes persist, articular cartilage health may be affected, as articular cartilage is sensitive to load characteristics. 14 Some limitations related to these EKP studies [11][12][13] are that perceived pain levels peaked relatively quickly (approximately 2-5 minutes), were not consistent over time, and completely resolved relatively quickly (approximately 15 minutes). It is unknown whether EKP that is maintained over a longer duration (.5 minutes) affects knee biomechanics similarly.…”

Reduction in knee adduction moment via non-invasive biomechanical training: A longitudinal gait analysis study

“…Vast evidence supports the role of biomechanical factors in the pathophysiology of this disease (Radin et al, 1991). Abnormal joint loads have been related to the development and progression of the arthritic process (Radin et al, 1991;Roemhildt et al, 2010).…”