How exercise influences equine joint homeostasis

Abstract

The maintenance of joint homeostasis is integral to joint health. Knowledge of the influence of exercise on joint homeostasis is not only relevant for determining sustainable levels of equine athletic training, but also for the study of early development of osteoarthritis or cartilage repair in animal models. This review provides an overview of findings derived from in vivo studies and postmortem analyses investigating exercise effects on various joint tissue components in the horse, supplemented where appropriate with data from small animal models. The concept of joint homeostasis and possible methods to quantify this are also discussed, with special attention to the potential benefits and pitfalls of biomarker analysis in synovial fluid. The main conclusion is that biomechanical loading in the form of deliberate exercise has a major influence on the delicate homeostatic balance within the tissues constituting the diarthrodial joint and on their interactions, which is crucial for proper and durable joint function. The amount and intensity of exercise can have a lasting effect on tissue characteristics in juvenile animals, but affects joint homeostasis in mature animals and can affect the delicate balance between physiologic adaptation and development of pathology. Biomarkers in synovial fluid can be helpful in assessing joint homeostasis, but their use and interpretation require caution and are often far from straightforward.