Human studies evaluating dGEMRIC as a prognostic tool for knee osteoarthritis

Abstract: Osteoarthritis (OA) is the most common joint disorder worldwide, causing joint pain and stiffness. The current gold standard for diagnosing knee OA is radiography. However, the disease has often progressed well beyond the point of no return once radiographic cartilage changes become visible. Identifying changes in cartilage at an early stage of OA would allow curative or prophylactic treatment to be instigated much earlier than today. Early in the progression of the disease, the articular cartilage is depleted of glycosaminoglycans (GAGs), which are responsible for cartilage load distribution and compressive stiffness. Delayed gadolinium-enhanced magnetic resonance imaging of cartilage, abbreviated dGEMRIC, can be used to estimate the GAG content of cartilage. A contrast medium is used, the concentration of which in the cartilage is inversely proportional to the amount of GAG. The purpose of this work was to evaluate dGEMRIC as a prognostic tool for knee cartilage changes and knee OA in humans. It was found that dGEMRIC could be used to predict the development of radiographic knee OA in patients at risk of developing OA. An association was also found between dGEMRIC values and important features of knee OA, such as joint space narrowing and osteophytes (bony changes). Unloading of joints has previously been shown to affect the constituents of cartilage. The knees of patients with ankle fractures, prescribed unloading of the injured leg for six weeks, were investigated. Unloading resulted in a measurable effect on the constituents of the knee cartilage, seen as a decrease in GAG content and an increase in the range of dGEMRIC values. These findings should be taken into account when considering treatment of patients involving an unloading regimen. Anterior cruciate ligament (ACL) injury has previously been shown to be an important risk factor for the development of OA. Patients who had sustained an ACL injury 20 years earlier, who had not undergone ACL reconstruction, were investigated. Notably, these patients showed good cartilage quality and subjective knee function, similar to that in healthy reference groups. This is an important finding and should be considered when recommending treatment for patients with ACL injuries.