The purpose of this study is to perform a detailed morphological analysis of the changes that occur at the attachment sites of muscles, tendons, and ligaments on the radius. We consider the osteological, anatomical, and pathological aspects in detail, devising a visual standard for ranking the development of osseous expression at each attachment. We also discuss the etiology, particularly through focus on the relationship with the activity and age variables. In a sample of 148 radii from archeological and contemporary samples, 11 osteological sites were analyzed in each specimen. The osteological sites included nine muscular attachments, the attachment of the interosseous membrane, and the groove of the extensor pollicis longus tendon. The results show that mechanical loading is the main cause of different types of markings appearing and developing on the bone surface. Furthermore, there is a relationship between the osteological appearance of enthesis and its morphological type. It is possible to grade osteological appearance with a visual reference method that establishes an identifiable threshold for each grade and eliminates relying completely on observer experience. This methodology is applicable to the field of physical anthropology and to its forensic subfield, identifying individuals by attributing to them specific work or given activities through the use of skeletal remains. Anat Rec Part A, 288A:794–805, 2006 © 2006 Wiley-Liss, Inc.