Patients with femoral head osteonecrosis can be asymptomatic and the diagnosis can be made from imaging performed for another indication. The vast majority of symptomatic patients complain of progressive pain localized to the groin and general hip region. While pain localized to the groin is most specific for intra-articular pathology, pain in the thigh and buttock is also commonly seen. These symptoms can be exacerbated with weight bearing and with combined flexion and internal rotation. Patients should be asked about prior history of trauma, surgery, corticosteroid use, ethanol use, and personal or family history of blood disorders. Sudden inability to bear weight associated with fevers, chills, weight loss, and/or night sweats warrant further workup for infectious, inflammatory, and or malignant underlying etiologies. Physical examination findings can often be nonspecific. Patients may walk with a mild antalgic gait favoring the affected side, but otherwise the majority of examination findings are normal during early stages of the condition. Any neurovascular deficits or isolated muscular weakness should be further worked up for other underlying etiologies.

All patients with suspected osteonecrosis of the femoral head should undergo a complete radiographic workup including an anterior–posterior (AP) view of the pelvis, an AP view of the affected hip, and a cross-table or frog-leg lateral view of the affected hip. Often, it is the lateral view that best demonstrates subchondral collapse and/or collapse. The most commonly utilized classification systems for osteonecrosis are based on radiographic findings and historically include the Ficat classification [13], and more recently the Steinberg classification (Table 2) [14]. Of note, patients who are diagnosed with AVN in another area of the body (i.e., humeral head) should always get hip radiographs as there is an increased risk of having concomitant (but asymptomatic) femoral head AVN [15]. Radiographs can remain completely normal for months after symptoms begin (Fig. 1). Early radiographic findings of osteonecrosis will show mild density changes within the femoral heads due to micro-infarcts with corresponding calcification. In both of these systems, stage III will show a crescent sign radiographically, indicating subchondral collapse (Fig. 2). Typically, advanced imaging with magnetic resonance imaging (MRI) is also employed if there is a high index of suspicion and/or the patient is at risk (i.e., alcoholic) despite normal radiographs. This modality can reveal changes due to osteonecrosis at earlier stages than plain radiographs are capable of showing. MRI has been shown to have excellent specificity and sensitivity with regard to osteonecrosis and will typically appear bright on T2-weighted images with corresponding dark findings on T1-weighted images. Bone scan is also another modality that can be used to help diagnose and stage osteonecrosis of the femoral head, but is not as specific as MRI [16, 17].

The patient is positioned supine on a traction table with a well-padded perineal post placed in the groin between the legs (Smith and Nephew hip traction system, Smith and Nephew, Andover, MA). Traction is applied with the leg in neutral extension, axially distraction, and adduction to provide a cantilever moment to the operative hip.

The greater trochanter and anterior superior iliac spine borders are palpable landmarks used to identify appropriate portal placement. These are marked on the skin.

Under fluoroscopic visualization, a standard anterolateral (AL) portal is created 1 cm proximal and 1 cm anterior to the AL aspect of the greater trochanter. The 70° arthroscope is inserted over a guidewire. While viewing from the AL portal, needle localization is used to establish an anterior portal, penetrating the capsule at the 2 o’clock position. The anterior portal is approximately 1 cm lateral to the line drawn vertically from the anterior superior iliac spine (ASIS) and a line drawn horizontally from the AL portal.