Hip Flexor Tendinitis

Anatomy

The iliopsoas musculotendinous unit consists of the iliacus muscle, arising from the iliac wing of the pelvis, and the psoas muscle, arising from the vertebrae of the lumbar spine. Tendons from both muscles exit anteriorly over the brim of the pelvis and join into a single tendon, inserting onto the lesser trochanter of the femur. Contraction of these muscles results in the flexion and external rotation of the hip. Extension and internal rotation of the hip places these muscles on stretch. The iliopsoas bursa, a synovial fluid–filled sac, is the largest bursa in the body and separates the iliopsoas tendon from the underlying hip joint capsule and pelvis. Occasionally, the iliopsoas bursa communicates with the capsule of the hip joint.

Etiology

Injury to the iliopsoas musculotendinous unit and the associated bursa can occur as a result of significant trauma, such as a blow to the hip or a sudden forceful extension, or from microtrauma due to repetitive hip flexion/extension activity. The resulting musculotendinous injury can vary from contusion to strain to a tendon tear or avulsion of the tendon at the lesser trochanter. The accumulation of repetitive microinjuries to the tendon results in disordered collagen healing, yielding weaker tissues prone to further injury. In contrast, injury to the bursa causes inflammation and enlargement due to increased synovial fluid production within the bursa and/or hypertrophy of the synovium. The resultant mass effect causes friction between the tendon and the bursa, resulting in secondary [Page 659]inflammation and injury to the musculotendinous unit.

History

Patients present with anterior hip pain associated with activity and may complain of an audible/palpable snapping of the hip. An inguinal mass may also be present.

Pain is characteristically noted in the groin or inguinal region of the hip, is aggravated by hip activity and relieved by rest, and may radiate from the hip to the knee. Patients with a traumatic history may note a snap in the hip at the time of injury, followed by pain and limping. Patients with an insidious onset of symptoms are often involved in work or sports that demand repetitive or vigorous hip activity over a wide range of motions, including running, track-and-field events, ballet, rowing, kicking sports, and strength training. Following injury, patients may experience symptoms with daily activities such as walking, climbing stairs, or standing from a seated position.

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