Atraumatic Instability

Due to a lack of a discrete acute event, the etiology of hip pain in the absence of trauma may be more difficult to determine. Furthermore, the differential diagnosis of hip pain is quite broad (Table 1). Based on the history and physical examination, various categories can be eliminated and the differential diagnosis further narrowed. The history should assess the timing of the onset of symptoms, the qualitative nature of the discomfort (pain, clicking catching, instability, stiffness, weakness), the specific location of the discomfort, and the precipitating cause of the symptoms [1,7].

Atraumatic instability can occur due to overuse or repetitive motion. This is a common complaint in athletes who participate in sports involving repetitive hip rotation with axial loading (ie, figure skating, gold, football, baseball, martial arts, ballet, gymnastics, and so forth). The history provides the greatest clues to the diagnosis because patients can usually describe the motion that causes the pain such as swinging a golf club during a drive or throwing a football toward the sideline. These repetitive stresses may directly injure the iliofemoral ligament or labrum and alter the balance of forces in the hip. These abnormal forces cause increased tension in the joint joint capsule, which can lead to capsular redundancy, painful labral injury, and subsequent microinstability. On physical examination, patients will usually experience anterior hip pain while in the prone position with passive hip extension and external rotation [1,7].

Once the static stabilizers of the hip including the iliofemoral ligament and labrum are injured, the hip must rely more on the dynamic stabilizers for stability. It is hypothesized that when capsular laxity is present, the psoas major, a dynamic stabilizer of the hip, contracts to provide hip stability. Over time, this condition can lead to stiffness, coxa saltans, or flexion contractures of the hip [14]. In addition, due to the origin of this muscle from the lumbar spine, a chronically contracted or tightened psoas major may be a major contributor to low back pain. Thus, hip instability or capsular laxity can trigger a whole spectrum of disorders that the physician must take into consideration when considering various treatment options.

In addition to screening plain radiographs, an MRI is critical for the further workup of unexplained hip pain. An MRI allows for high-resolution imaging

Table 1

Differential diagnosis of hip pain

Primary labral pathology

Non-musculoskeletal causes

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