Gait alterations increase friction of degenerated articular cartilage: A tribological study

To investigate the effect of gait alterations associated with osteoarthritis (OA) on the frictional properties of porcine articular cartilage (AC) in intact and degenerative conditions.

Forty-eight cylindrical AC samples were harvested from 12 porcine femur condyles and equally divided between four groups with n = 12 samples each: fresh intact control (Ctr^fresh), mechanical surface damage (OA^mech), enzymatically degraded with chondroitinase ABC to mimic OA-related glycosaminoglycan depletion (OA^enzym) and a buffer-incubated control (Ctr^buffer). Friction experiments were performed in a dynamic tribometer with a cartilage-against-glass configuration. Four gait-like loading profiles were applied for 10 min in a randomised order: normal gait, reduced walking speed with physiologic stance phase loading, altered stance phase loading with normal walking speed and OA specific gait with both, altered stance phase loading and reduced walking speed. Friction coefficients were calculated both at the beginning (µ₀) and end of testing (µ_end) for both the stance- and swing phase conditions. Statistical analyses were carried out with linear mixed models.

In intact AC samples (Ctr^fresh, Ctr^buffer), friction did not differ between the four gait patterns. In both OA groups (OA^mech, OA^enzym), the OA-specific gait resulted in the highest friction (µ_end > 0.03), which was always significantly higher (p < 0.05) than the values assessed under normal gait (µ_end > 0.01).

OA gait increased friction only in degenerated AC. The combination of altered stance phase loading and reduced walking speed characteristic of OA gait may disrupt biphasic lubrication mechanisms, thereby contributing to increased friction. This might be important because it is assumed that altered friction is involved in OA pathogenesis. From a tribological perspective, gait retraining should be considered in OA prevention and its conservative management to mitigate the effect of alterations in gait on the tribological functionality of the AC.

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