Application—Application of Infrared Thermography as a Diagnostic Tool of Knee Osteoarthritis

Application of Infrared Thermography as a Diagnostic Tool of Knee Osteoarthritis

   Through its involvement in the activities of most humans, the knee is likely to be the seat to many diseases and injuries like osteoarthritis. Osteoarthritis is a degeneration of the cartilage without infection or special inflammation. This multi-factorial disease led to a more or less rapid destruction of cartilage that coats the ends of bones. Anatomically, this destruction is accompanied by a proliferation of bone under the cartilage. During cartilage destruction, small pieces of cartilage may break off and "float" in the articular pocket: then they trigger inflammatory attacks that result in mechanical hyper-secretion of fluid and swelling of the joint.

   Osteoarthritis is a chronic disease and a major cause of pain. 7-11% of the populations in developed countries are suffering from symptomatic OA. Over the last twenty years, many studies have focused in part on the effect of certain risk factors such as sport, age, overweight and partly on the different diagnostic techniques like radiography, arthroscopy, the method of Lechman (CT) and magnetic resonance imaging (MRI). However, little research has been devoted to the thermal aspects associated with osteoarthritis of the knee before and after exercise.

Figure 1. Infrared thermography of right and left knees.

   However, interest in IRT is up today because of improved devices and methods of calculation. The special characteristic of IRT studies is that we can get additional information about the skin's thermal aspect and about the complex thermoregulatory process. IRT gives a possibility to evaluate the effect of the sporting activity and to detect possible trauma or dysfunctions, which cannot be shown by present conventional methods, it can measure skin temperature over inflamed joints.

   Infrared thermography is a diagnostic method providing information on the normal and abnormal sensory and nervous systems, trauma, or inflammation locally and globally. Infrared thermography shows physiological changes rather than anatomical changes and could be a new diagnostic tool to detect the pathology of the knee.

Figure 2. Infrared thermography of right and left knees before and after race for a participant with right knee OA.

   This paper aimed to study the feasibility of application of infrared thermography to detect osteoarthritis of the knee and to compare the distribution of skin temperature between participants with osteoarthritis and those without pathology. Ten participants with knee osteoarthritis and 12 reference healthy participants without OA participated in this study. The participants with osteoarthritis of the knee were selected on clinical examination and a series of radiographs. The level of pain was recorded by using a simple verbal scale (0-4). Infrared thermography reveals relevant disease by highlighting asymmetrical behavior in thermal color maps of both knees. Moreover, a linear evolution of skin temperature in the knee area versus time has been found whatever the participant group is in the first stage following a given effort. Results clearly show that the temperature can be regarded as a key parameter for evaluating pain. Thermal images of the knee were taken with an infrared camera. The study shows that with the advantage of being noninvasive and easily repeatable, IRT appears to be a useful tool to detect quantifiable patterns of surface temperatures and predict the singular thermal behavior of this pathology.

Reference

Ahlem ARFAOUI, Mohamed Amine BOUZID, Hervé PRON, et al. Application of Infrared Thermography as a Diagnostic Tool of Knee Osteoarthritis. Journal of Thermal Science and Technology. 7(1):227-235, 2012.