Final answer:
When the site of a lesion is unknown and the leg doesn't fit on one IR, include the joints proximal and distal to the suspected area in radiographs. Arthrography can be used to diagnose joint conditions effectively, such as RA, by visualizing soft tissue structures with a contrast agent.
Step-by-step explanation:
When the site of a lesion is unknown in leg radiography, it's important to include the joints proximal and distal to the suspected area of injury or disease. If the leg is too long to fit on one image receptor (IR) for radiographs, both the knee and ankle joints should be included for the lower leg, and the hip and knee joints should be included for the thigh. This is important to check for pathologies such as fractures or degenerative changes that may not be localized to one specific area but could involve joint surfaces or articulate with other bones.
Arthrography could be an alternative imaging method used to diagnose conditions such as rheumatoid arthritis (RA). This technique uses a contrast agent to visualize soft tissue structures of joints, allowing for early detection of degenerative changes in cartilage before bone structures are affected. For comprehensive analysis, radiographs should target both the site of symptoms and potential adjacent areas of pathology, to ensure a thorough examination when the exact location of a lesion is unknown.