Lymph is protein rich fluid in the interstial space (tissue around the cells) and in the soft tissue. The lymphatic system is designed to move the lymph from the interstial space through delicate lymphatic channels, with interspersed lymph nodes, back to the heart. If the lymphatic system becomes damaged or becomes overwhelmed, the lymph accumulates and creates swelling in the soft tissue called lymphedema. Lymphedema most commonly occurs in the legs, but can occur in all parts of the body where there is soft tissue. Lymphedema is a very complicated condition with numerous causes.