From Leopard Gecko Wiki
MBD is the abbreviation for Metabolic Bone Disease. This is a very common disease with the novice owner, because the geckos are not supplemented with calcium. Some of the characteristics of MBD are bowed limbs, spongy jaw bone, lethargy, and sluggish movement. Also, many geckos will slowly lose weight since they are unable to move quickly without pain and unable to bite their food since their jaws are softened by the disease. If you suspect your gecko has MBD, it should be taken to the vet ASAP. The most common treatments include separating the gecko into its own enclosure, vitamin D injections once per week for 2 weeks and administration of liquid calcium. MBD is NOT associated with impaction in any way.