120 Synovial Herniation Pit

CASE 120

Synovial Herniation Pit

Anthony G. Ryan and Peter L. Munk

Clinical Presentation

A 26-year-old woman presented with vague hip pain.

Figure 120A

Figure 120B

Radiologic Findings

An anteroposterior radiograph of the hip (Fig. 120A) shows an apparent ill-defined lucency with a surrounding rim of sclerosis projected through the superior aspect of the femoral neck.

A transaxial CT at the level of the lesion (Fig. 120B) on the radiograph confirms the presence of a lucent defect surrounded by a moderate sclerotic margin at the junction of the femoral head and neck.

Diagnosis

Synovial herniation pit (Pitt’s pit)

Differential Diagnosis

Osteoid osteoma
Geode

Discussion

Background

Patients very commonly present with hip pain that often is nonspecific in character. Virtually all of these patients will go on to have radiography. A frequently encountered finding is that of a synovial herniation pit.

Etiology

Although unclear, mechanical stress is thought to be responsible. The level of the herniation appears to be related to the thickest portion of the capsule and the ligaments in the hip joint, where the fibers of the zona orbicularis cross and intermingle with the iliofemoral ligament. This area becomes tightest in extension and internal rotation.