Abstract: Leg weakness is a regressive locomotory disease associated with osteochondrosis and osteoarthritis. However, there are no marked clinical symptoms and it is difficult to evaluate the prognosis or make a diagnosis before death. In humans joint markers to measure cartilage substances in blood are utilized. In particular, keratan sulfate specifically exists in cartilage. This parameter has been measured in dogs and horses. However, no study has reported measurement in pigs. Furthermore, age-/breed-related or gender differences are unclear. In this study, reserachers clarified the hemodynamics of keratan sulfate in pigs and confirmed that the keratan sulfate level decreased when leg weakness was clinically observed in the sow and growing pigs for breeding. In sows the blood level of keratan sulfate decreased to about 1/10 of that in piglets. This was possibly because a pig-specific breeding form with the stall was employed in sows affecting articular movement and reducing cartilage metabolism.