Imaging of the Acromioclavicular Joint: Anatomy, Function, Pathologic Features, and Treatment.

The acromioclavicular joint is an important component of the shoulder girdle; it links the axial skeleton with the upper limb. This joint, a planar diarthrodial articulation between the clavicle and the acromion, contains a meniscus-like fibrous disk that is prone to degeneration. The acromioclavicular capsule and ligaments stabilize the joint in the horizontal direction, while the coracoclavicular ligament complex provides vertical stability.

Adult Acquired Flatfoot Deformity: Anatomy, Biomechanics, Staging, and Imaging Findings.

Adult acquired flatfoot deformity (AAFD) is a common disorder that typically affects middle-aged and elderly women, resulting in foot pain, malalignment, and loss of function. The disorder is initiated most commonly by degeneration of the posterior tibialis tendon (PTT), which normally functions to maintain the talonavicular joint at the apex of the three arches of the foot. PTT degeneration encompasses tenosynovitis, tendinosis, tendon elongation, and tendon tearing.

Layered Approach to the Anterior Knee: Normal Anatomy and Disorders Associated with Anterior Knee Pain.

Anterior knee pain is a common complaint that can be caused by a wide spectrum of disorders affecting the many varied tissues at the anterior knee. The anatomy and pathologic conditions of the anterior knee can be approached systematically by organizing the region into four layers: (a) superficial layer of fat, fascia, and bursae; (b) functional layer composed of the extensor mechanism and patellar stabilizers; (c) intracapsular extrasynovial layer containing the fat pads; and (d) intra-articular layer. The superficial layer is composed of delicate tissues that are predisposed to blunt and penetrating trauma, irritation, and infection.

MR Imaging of Atraumatic Muscle Disorders.

Atraumatic disorders of skeletal muscles include congenital variants; inherited myopathies; acquired inflammatory, infectious, or ischemic disorders; neoplastic diseases; and conditions leading to muscle atrophy. These have overlapping appearances at magnetic resonance (MR) imaging and are challenging for the radiologist to differentiate. The authors organize muscle disorders into four MR imaging patterns: (a) abnormal anatomy with normal signal intensity, (b) edema/inflammation, (c) mass, and (d) atrophy, highlighting each of their key clinical and imaging findings.

MR Imaging of Muscle Trauma: Anatomy, Biomechanics, Pathophysiology, and Imaging Appearance.

Muscle is an important component of the muscle-tendon-bone unit, driving skeletal motion through contractions that alter the length of the muscle. The muscle and myotendinous junction (MTJ) are most commonly injured in the young adult, as a result of indirect mechanisms such as overuse or stretching, direct impact (penetrating or nonpenetrating), or dysfunction of the supporting connective tissues. Magnetic resonance (MR) imaging is widely used for assessment of muscle injuries.