Bone age estimation is important for monitoring growth, puberty, and predicting adult height. The hand wrist radiograph is commonly used, with the Greulich and Pyle (G-P) atlas and Tanner and Whitehouse methods assessing ossification centers. G-P matches radiographs to standard images while Tanner assigns scores to 20 bones. Other sites like the pelvis, elbow and knee can also indicate skeletal maturity through fusion of centers.