Chondroitin sulphate: an effective joint lubricant?

Objective: The effect of chondroitin sulphate (CS) treatment on the friction and deformation characteristics of native and glycosaminoglycan (GAG) deficient articular cartilage was investigated. Methods: Friction tests were conducted at 0.4 MPa load, in Static and Dynamic models, to determine the startup coefficient of friction (COF) and dynamic COF, respectively. Native cartilage: For each cartilage pin and plate couple, the COF was determined under three consecutive tests - (1) baseline COF in PBS (2) COF in CS lubricant and (3) COF again in PBS, after 24 h CS treatment. GAG deficient cartilage: For each cartilage pin and plate couple, the baseline COF was determined in PBS initially and again following enzymatic treatment to deplete GAGs. The specimens were then soaked in CS solution for 24 h and the COF determined again in PBS. In a similar manner, friction tests were replaced with indentation tests to study the deformation of the tissue. Results: CS at 50 mg/ml significantly lowered the startup COF of native cartilage both as a lubricant and a treatment solution. In the dynamic model, where the fluid load support is sustained at a high level, CS failed to have any effect on the COF of native cartilage. GAG depletion raised the friction and deformation levels of cartilage, and subsequent CS treatment failed to lower them to their native levels. Conclusion: CS proved to be an effective lubricant for cartilage under mixed-mode lubrication conditions. However, supplemental CS that diffused into the specimens had no influence on the fluid load support of cartilage.