Final answer:
The first step in the musculoskeletal assessment of a 2-year-old by a student nurse should be to visually inspect the child's body for obvious signs of abnormality before moving on to more direct forms of examination.
Step-by-step explanation:
When a student nurse is performing a musculoskeletal assessment on a 2-year-old, the most appropriate step to begin with is to inspect the body visually. This non-invasive approach provides an initial assessment of the child's overall physical condition, looking for any obvious signs of injury, deformities, or asymmetries in the body's structure. Moreover, starting with a visual inspection helps in gaining the trust of a young child and can guide subsequent parts of the physical examination such as palpation and range of motion exercises.