Ultrasonography is a useful tool in understanding rheumatic conditions and in diagnosis and management. Much of the investigation into the validity of ultrasonography and its clinical use has been undertaken in inflammatory arthritides. Although ultrasonography has been applied to osteoarthritis (OA) in clinical practice, there has been little investigation into the validity of ultrasonography in OA or its utility in clinical trials or routine clinical practice. This review outlines benefits and limitations of imaging OA with ultrasonography. © 2009 Elsevier Inc. All rights reserved.