Standing plain radiography is appropriate for this patient who most likely has osteoarthritis. Osteoarthritis is often clinically identifiable by the presence of bony hypertrophy in a characteristic pattern of joint involvement and the absence of overt inflammatory synovitis. The history generally consists of long-standing and gradually worsening symptoms in middle-aged or older patients. Confirmatory plain radiographs are appropriate to solidify the diagnosis and rule out less common findings such as osteonecrosis, fractures, or malignancies. They are also noninvasive, widely available, and the least expensive radiographic modality. Standing views of the knees can demonstrate a more accurate picture of the joint-space narrowing that is present during functioning, including standing and walking, than radiographs that are obtained supine.

Bone scintigraphy can visualize areas of bone turnover change due to osteophyte formation, subchondral sclerosis, subchondral cyst formation, and bone marrow lesions. However, its limited anatomic resolution and the use of ionizing radiation make it less useful for the diagnosis of osteoarthritis.

MRI is capable of demonstrating numerous findings in soft tissue and cartilage that provide information about the joint as a whole organ. As such, MRI is a critical tool in osteoarthritis research, but its high cost argues against its routine use, particularly because there are no end points apart from joint-space narrowing (easily assessed on plain radiographs as well) visualized on MRI that confer prognostic information.

Although ultrasonography is noninvasive and is appealing because it provides real-time information, its primary use in the management of osteoarthritis is for needle placement in difficult arthrocenteses. Limitations of ultrasonography include that it is an operator-dependent technique and that the physical properties of sound limit its ability to assess deep articular structures and the subchondral bone.