This paper describes the role of sceletal system in animals, its composition, structure and anatomy of bones. Terms osteoblast, osteocyte, osteoclast and extracellular matrix are explained as well as types of bone tissue and classification of bone based on shape, function and localization. The biomechanics of bone fracture describes the mechanical and structural characteristics of healthy bone and the forces acting on it, and the knowledge of biomechanical force and the mechanical principles used to stabilize fractures in bone healing. Subsequently, the classification of the bone fracture is divided according to the cause of fracture occurrence, the extent of changes, the complexity of the fractures, the integrity of the surrounding soft tissues, the continuity line, the location of the fracture, the number and characteristics of the fractured fragments, and the ratio and position of the fragments. Each is individually described. Bone fracture diagnostics highlights radiological diagnostics as the best method for testing skeletal disorders and provides indications for its use. The appearance of the bone on the X-ray is also described with respect to the type of bone and age of the animal. The processes of primary and secondary bone healing and the impact of implant on bone healing are explained. Also listed and described are complications that can occur during bone healing, which are: delayed healing and incoordination, irregular healing, osteomyelitis, sequestration, and healing complications in places touching the implants. Finally, a mnemonic interpretation of osteosynthesis is described and defined, and examples of the evaluation of the outcome of osteosynthesis by the A4 system are presented.