Hypothesis 3: Congenital Deformity The fact that the foal is only a few days old strongly supports the hypothesis that the problem could be congenital. Equine congenital deformities have a wide range of possible etiologies, including abnormal intrauterine positioning, chemical insults, hormonal imbalances, nutritional imbalances, unfavorable conformation, trauma, or immature musculoskeletal tissues. The deformities typically manifest within the first few days of life, typically presenting as lameness. The deformities can be due to laxity of the periarticular supporting structures. As the foal develops strength of the musculotendonous and ligamentous structures, the deformities resolve. The deformity could also be caused by incomplete ossification of the tarsal bones. In foals with incomplete ossification, the ossification centers of tarsal bones are smaller and more spherical than normal. The stresses of normal weight bearing usually results in angular limb deformities. Deformities can also be caused by asymmetric growth of the metaphysis/epiphysis. Trauma in the form of asymmetric pathiologic compressive forces on the growth cartilages has been implicated as a major cause of asymmetric growth. Any of the above deformities can cause inappropriate pressure on the joint and limb, resulting in inflammation. Inflammatory mediators such as cytokines and leukotrienes are attracted to the site, and result in pain. Pain also occurs from direct nociceptor stimulation caused by the inappropriate pressure in the area. This pain is consistent with the physical exam. Radiographs and/or ultrasound can be used to detect the bone abnormalities, and will either confirm or rule-out this hypothesis.