SUMMARY:LSTVs are common within the spine, and their association with low back pain has been debated in the literature for nearly a century. LSTVs include sacralization of the lowest lumbar vertebral body and lumbarization of the uppermost sacral segment. These vertebral bodies demonstrate varying morphology, ranging from broadened transverse processes to complete fusion. Low back pain associated with an LSTV may arise from the level above the transition, the contralateral facet when unilateral, and/or the anomalous articulation when present. Although this association is still somewhat controversial, beyond dispute is the importance of identifying an LSTV in patients in whom a surgical or interventional procedure is planned. This is essential to avoid an intervention or surgery at an incorrect level. In this article, each of these issues will be addressed with attention to identifying and correctly numbering LSTVs as well as detecting imaging findings related to the genesis of low back pain.ABBREVIATIONS: AP ϭ anteroposterior; LSTV ϭ lumbosacral transitional vertebra L STVs are congenital spinal anomalies defined as either sacralization of the lowest lumbar segment or lumbarization of the most superior sacral segment of the spine. LSTVs are common in the general population, with a reported prevalence of 4%-30%.1-15 The degree of morphologic variation of these segments ranges from L5 vertebrae with broadened elongated transverse processes to complete fusion to the sacrum. Conversely, the S1 vertebral segment can show varying degrees of lumbarization, such as the formation of an anomalous articulation rather than fusion to the remainder of the sacrum, well-formed lumbar-type facet joints, a more squared appearance in the sagittal plane, as well as a well-formed fully-sized disk, rather than the smallersized disk typically seen between S1 and S2.

Epicondylitis commonly affects the elbow medially or laterally, typically in the 4th or 5th decade of life and without predilection with regard to sex. Epicondylitis is an inflammatory process that may be more accurately described as tendinosis. In the lateral epicondylar region, this process affects the common extensor tendon; in the medial epicondylar region, the common flexor tendon is affected. The condition is widely believed to originate from repetitive overuse with resultant microtearing and progressive degeneration due to an immature reparative response. Advances in understanding of the anatomy and pathophysiology of epicondylitis have shaped current treatment practices. Conservative measures are undertaken initially, because symptoms in most patients improve with time and rest. Those who fail to respond to conservative therapy are considered for surgical treatment. When surgery is contemplated, magnetic resonance imaging or ultrasonography is useful for evaluating the extent of disease, detecting associated pathologic processes, excluding other primary sources of elbow pain, and planning the surgical approach. Familiarity with the normal anatomy, the pathophysiology of epicondylitis and its mimics, and diagnostic imaging techniques and findings allows more accurate diagnosis and helps establish an appropriate treatment plan.

The elbow, a synovial hinge joint, is a common site of disease. Ultrasonography (US) has become an important imaging modality for evaluating pathologic conditions of the elbow. This powerful imaging tool has the advantages of outstanding spatial resolution, clinical correlation with direct patient interaction, dynamic assessment of disease, and the ability to guide interventions. Unlike most other imaging modalities, US allows the contralateral elbow to be imaged simultaneously, providing an internal control and comparison with normal anatomy. A useful approach to US evaluation of the elbow is to divide it into four compartments: anterior, lateral, medial, and posterior. US of the elbow has varied clinical applications, including evaluation and treatment of lateral and medial epicondylitis, imaging of biceps and triceps musculotendinous injuries, evaluation of ulnar collateral ligament laxity, diagnosis of joint effusions and intraarticular bodies, and evaluation of peripheral nerves for neuropathy and subluxation. US can also be used to evaluate soft-tissue masses about the elbow. Knowledge of the normal US anatomy of the elbow, familiarity with the technique of elbow US, and awareness of the US appearances of common pathologic conditions of the elbow along with their potential treatment options will optimize radiologists' diagnostic assessment and improve patient care. Supplemental material available at http://radiographics.rsna.org/lookup/suppl/doi:10.1148/rg.334125059/-/DC1.

Delamination tears occur most often in the supraspinatus tendon, and in our series always involved the articular surface of the tendon. Only half of these tears have a visible cleavage plane in the interstitium, but this cleavage plane is not necessary for diagnosis if the torn edge is retracted.

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