The acetabular fossa constitutes the inferior portion of the acetabulum and is surrounded by the lunate surface in its superior and lateral aspects ( Fig. 54.1 ).

Bony anatomy of the hip.

When performing hip arthroscopy, it is critical to understand the location of the pathology. To locate chondrolabral hip lesions more easily, the socket is considered a clock, wherein 12 o’clock represents the most superior aspect of the acetabulum, continuing anteriorly with successive hours. Unlike the knee, the 3 o’clock position is always anterior for both right and left hips.

Several bony landmarks have been described to help the surgeon with an accurate location during arthroscopy:

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  The superior extent of the anterior labral sulcus (psoas-u) indicates the 3 o’clock position on the acetabular rim; anteriorly, it corresponds to the location of the iliopsoas tendon.

  
  
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  The stellate crease is located superior to the apex of the acetabular fossa and corresponds to the 12 : 30 position (see Fig. 54.1 ).

The abduction angle of the acetabulum relative to the horizontal plane averages 45 degrees with 20 degrees of anteversion.

The femoral head forms roughly two-thirds of a sphere whose surface is completely articular except for the fovea capitis femoris where the ligamentum teres (ligament of the head of the femur) is attached (see Fig. 54.1 ).

On an average, the neck shaft angle averages 130 degrees and the femoral neck is anteverted 14 degrees relative to the bicondylar axis at the knee.

The labrum is a fibrocartilaginous structure attached to the acetabular rim.

It is responsible for guaranteeing the suction seal, a key function in fluid dynamics, ensuring wider coverage of the femoral head and providing negative intra-articular pressure that provides stability to the hip joint.

Labral pathology is normally observed in the anterosuperior area of the socket (12 to 2 o’clock position); this area correlates with the location where impingement normally occurs ( Fig. 54.2 ).

Arthroscopic image of a left hip demonstrating a tear in the superolateral aspect of the labrum.

Note also the inflammation of the labrum confirming a pathologic process.

The hip capsule is formed by the iliofemoral ligament anteriorly, the ischiofemoral ligament posteriorly, and the pubofemoral ligament inferiorly (see Fig. 54.1 ).

Near the acetabular origin, the superior and superolateral aspect of the capsule is the thickest portion (3.7–4.0 mm) ( Fig. 54.3 ).

Left Hip With an Intraportal Capsulotomy.

Note the thickness of the capsule at several locations (thickest at its superolateral portion).

The capsule is inserted at a mean of 26.2 mm distal to the chondral head–neck junction of the proximal femur. The capsule has a spiral configuration that tightens in terminal extension and external rotation.

Gluteal group: Gluteal muscles include the gluteus maximus, gluteus medius, gluteus minimus, and tensor fasciae latae.

The gluteus medius muscle stabilizes the hip and controls hip motion, particularly during weight bearing. Weakness or insufficiency of this muscle leads to the Trendelenburg gait.

Adductor group: Adductor brevis, adductor longus, adductor magnus, pectineus, and gracilis muscles; the adductors originate on the pubis and insert on the medial, posterior surface of the femur, with the exception of the gracilis, which inserts distally on the pes anserine on the tibia. There is a pubic aponeurosis that is a confluence of the adductor and gracilis origins; it is also referred to as rectus abdominis/adductor aponeurosis . There is a clinical association between FAI and sports hernia and adductor tendinopathy, also known as athletic pubalgia .

Iliopsoas group: Composed of the iliacus and psoas major muscles; the iliacus originates on the iliac fossa of the ilium and joins the psoas major muscle that runs from the lumbar bodies (2, 3, 4) and inserts distally into the lesser trochanter.

The rectus femoris is a weaker flexor with the knee in extension. However, owing to its proximity to the capsule and its complex anatomy, it serves as an important differential diagnosis for hip pain.

The direct head of the rectus femoris attachment has a shape of a “tear drop” occupying the entire footprint of the superior facet of the anterior inferior iliac spine (AIIS). The indirect head has a broad insertion over the rim ( Fig. 54.4 ).

Muscles and insertions of pelvis, hip, and thigh.

This group consists of the obturator externus and internus, the piriformis, the superior and inferior gemelli, and the quadratus femoris (see Fig. 54.4 ). The piriformis muscle originates in the anterior surface of the sacrum and inserts into the superior boundary of the greater trochanter; the gemellus superior goes from the ischial spine and joins the piriformis tendon in its insertion at the greater trochanter. The obturators (internus and externus) insert on the medial and lateral surface of the obturator membrane and then travel to the medial surface of the greater trochanter and the trochanteric fossa, respectively. The gemellus inferior muscle inserts on the superior aspect of the ischial tuberosity and inserts distally into the piriformis tendon (indirectly to the greater trochanter). Last, the quadratus femoris muscle goes from the lateral edge of the ischial tuberosity to the intertrochanteric crest.

Acute onset of hip pain is more likely to be due to a specific pathology, which may be diagnosed through physical examination and imaging.

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  These injuries are typically easier to treat and carry a more favorable prognosis.

Gradual onset of hip pain is likely to be due to (i) chronic disease or (ii) pain syndromes, which may be difficult to diagnose.

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  These injuries typically carry a worse prognosis and require more complex methods of treatment.

Examine patient’s gait and stance.

Examine patient’s posture in supine and seated positions, looking for internal or external rotation of the injured limb at rest, or a flexion contracture of the hip joint.

Check for asymmetry in leg length, muscle atrophy, or pelvic obliquity.

When performing these measurements, it is important to assess if the range of motion (ROM) is limited or excessive; this will help differentiate between two different pathologies (impingement vs. dysplasia).

Clinically, leg length can be measured from the ASIS to the medial malleolus.

ROM should be measured bilaterally to compare the injured and noninjured sides. Hip flexion, extension, abduction, adduction, and internal and external rotation should be measured. Internal and external rotation should be assessed both with the patient supine, at 90 degrees of hip flexion, and prone with the hip at neutral. This last position will help define the patient’s femoral version. Patients with excessive anteversion of the femur will have excessive internal rotation (IR) when they are prone and with the hip neutral.

The patient should be asked to point to the single most painful location; this will provide helpful clues as to the potential diagnoses.

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  Patients with hip pain will normally do the “ C sign,” grabbing their hip in a C -shape with their hand.

  
  
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  Patients with posterior pelvic pain may also have associated groin pain, lateral thigh pain, or anterior thigh pain.

  
  
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  Posterior pelvic pain may be associated with labral tear, developmental dysplasia of the hip (DDH), and/or FAI.

Palpation should begin away from the source of the patient’s pain and progressively move closer to the painful location.

The following anatomic sites should be palpated to assess for significant pain: lumbar vertebrae, sacroiliac (SI) joint, ischium, iliac crest, greater trochanter, trochanteric bursa, muscle bellies of the thigh and hamstrings, and pubic symphysis.