Book excerpt: Developmental biology of normal bone and cartilage including histogenesis, molecular/gene and biomechanical aspects is updated and expanded. The book outlines the biology of: bone repair with differing mechanical environments; cartilage repair at articular and physeal sites; and distraction osteogenesis. The generously illustrated text provides an in-depth presentation of the interplay between normal developmental biology, abnormal pathologic states and the influence of operative and non-operative orthopedic interventions on childhood orthopedic deformity. Thirty-four principles underlying the development, progression and management of skeletal deformity in the growing child are defined. Orthopedic management including surgical treatment is discussed for: skeletal dysplasias; epiphyseal growth plate fracture-separations; lower extremity length discrepancies; and deformities of joints and epiphyses due to metabolic, inflammatory, infectious, hematologic, and neoplastic disorders. Treatments are related to extent of deformity, remodeling post-surgery and possible recurrence. This 2nd edition of Pediatric Orthopedic Deformities has been expanded to cover more regions and disorders and is being presented in 3 volumes.