Leaky gut syndrome is when the lining of the digestive tract known as the intestinal mucosa becomes weakened. Its usual job is to allow nutrients into the bloodstream and protect the body from larger, harmful particles. With leaky gut, the mucosal gut lining will allow things like bad bacteria, undigested food particles and toxic waste to leak into the blood stream. This can damage the immune system and cause overall inflammation in the body. Joint disease can be just one of many possible leaky gut symptoms.