Osteoarthritis is one of the most common disorders of joints. The joints most affected are the hip, knee, shoulder, the great toe and the base of the thumb. Degeneration of articular cartilage, leading to osteoarthritis, can occur without any predisposing factors or can be secondary to an associated condition, including a traumatic event or repetitive occupational-related trauma. Articular cartilage degeneration is a gradual process and the findings on radiographic imaging are dependent on the stage. The description and gradation of osteoarthritis (e.g. localized or diffuse and mild, moderate or severe ) is used by the referring physician in determining treatment options. Treatments include conservative therapy (e.g. physical therapy, alteration in precipitating event, oral medications, or intraarticular steroid injections), or surgical treatment (e.g. osteotomies or joint replacement).
Conventional Radiographs - Routine X-ray Examinations
Regardless of the joint, osteoarthritis has characteristic findings on conventional radiographs (X-rays) distinctive from other joint disorders such as rheumatoid arthritis. Osteoarthritis presents with localized nonuniform joint space narrowing. The joint narrows secondary to localized cartilage loss. Cysts or fluid-filled cavities can form in the bone secondary to chronic impaction of bone on bone contact. Osteoarthritis is the result of the body's response to cartilage destruction and the bodies attempt to stabilize the joint. In the absence of an effective cartilage buffer, there is chronic friction on the narrowed joint space. Sclerosis (increased bone density) results as the body lays down bone in response. The localized cartilage wear or loss results in incongruous joint surfaces and osteophytes (bone spurs) around the joint margins form in an attempt to stabilize the joint. There are basic routine X-ray views for imaging each joint an AP (anterioposterior, or a frontal view), one or two oblique views, and a lateral view are standard. At Hospital for Special Surgery, special X-ray views that are designed to increase the sensitivity of the conventional radiographic study in detecting early changes are typically used in place of or in addition to the standard views.
Specialized Diagnostic Imaging Examinations
Clinical signs of osteoarthritis may be evident before they are observed on conventional radiographic views. At Hospital for Special Surgery, MRI, CT and Ultrasound and are used in certain conditions because they are more sensitive for the detection of early osteoarthritis.
The Faculty of the Department of Radiology and Imaging at HSS are board certified radiologists with fellowship specialty training in musculoskeletal imaging and cross section (CT/MR/US) imaging. While various subspecialty physicians perform these procedures, Radiologists are physicians trained in the use of all forms of imaging and have specific training in the physics behind imaging and the safe use of ionizing radiation (fluoroscopy/CT) as well as MR and ultrasound safety.
Anesthetic and/or steroids injected into a painful osteoarthritic or joint can help reduce the pain. The advantage of having these injections performed using image guidance is that the needle tip is visualized and can confirm it is in the joint space. Direct visualization can be performed using fluoroscopy, CT or ultrasound guidance. A joint injection performed under fluoroscopy, which is real-time X-ray, or under CT guidance, is called an arthrogram. The radiologist will inject a small amount of contrast agent into the joint to confirm accurate needle placement. With ultrasound, the radiologist directly visualizes the needle in the joint, as well as neighboring muscles, arteries and veins.
At Hospital for Special Surgery, the frontal view is usually obtained with the patient weight bearing. A Merchant view of the patellofemoral joints (kneecaps) is also usually obtained.
Reviewed by Helen Pavlov, MD, FACR