Introduction
DISEASE
A major step forward in designing effective exercise therapy interventions for knee OA patients is to better understand the mechanisms why exercise therapy helps to alleviate OA symptoms, including a better understanding of the direct effect exercise therapy has on the cartilage turnover of the knee joint [A direct effect of exercise-related joint loading is believed to have a significant effect on cartilage turnover [Aggrecan and type II collagen are the two most abundant extracellular matrix proteins of the cartilage. In healthy subjects, there is a delicate balance between the remodeling of these components ensuring cartilage tissue homeostasis. In OA, a hallmark of the disease is the degradation of cartilage due to increased proteolytic activity. This activity results in the release of specific extracellular degradation fragments. In the VIDEX study, the a disintegrin and metalloproteinase with a thrombospondin type 1 motif (ADAMTS) generated aggrecan marker huARGS was used to quantify aggrecan degradation. Formation and degradation of type II collagen were assessed with the biomarkers PRO-C2 and C2M, respectively. These three biomarkers have previously been measured in serum samples from clinical OA trials and have shown to reflect changes in cartilage tissue turnover [The objective of this study was to investigate cartilage tissue turnover in patients with knee OA in response to a supervised 12-week exercise-related joint loading training program followed by a 6-month period of unsupervised gym training. A second objective was to study the difference in cartilage tissue turnover between HI and LI resistance training.