Anatomy
The Hip

Hip Anatomy

Where does the hip capsule run from?

Anteriorly – runs from the acetabular rim to the intertrochanteric line
Posteriorly – runs from acetabular rim to 1.5cm proximal to the intertrochanteric line

What ligaments surround the hip joint?

Three key ligaments surround the hip joint:

Pubofemoral
Iliofemoral
Ischiofemoral

The ligamentum teres sits within the hip joint running from the apex of the femoral head to the acetabular notch

Which of these ligaments is the strongest?

The iliofemoral ligament is a Y-shaped ligament that is the strongest ligament

Runs from rim of acetabular (from ileum) to the inter-trochanteric line
Resists hyperextension of the hip joint and is taut when standing - aiding in the maintenance of posture

Describe the blood supply to the femoral head?

Blood Supply to Femoral Head

Retinacular vessels
- Majority of blood supply comes via the retinacular arteries
- These provide a retrograde blood supply via an arterial anastomosis from the medial and lateral circumflex femoral arteries  originate from the profunda femoris artery
Nutrient vessels from medullary canal
Artery of ligament teres
- Branch of the obturator artery and runs within the ligamentum teres

What are the stabilisers of the hip joint?

Static

Ball and socket joint
Acetabular labrum
Ligaments
- Ligamentum teres
- Iliofemoral / Ischiofemoral / Pubofemoral ligaments

Dynamic

Muscles surrounding hip joint

Muscles Surrounding the Hip

Name the hip flexors and their innervations

Iliopsoas
Sartorius
Rectus Femoris
Pectineus

All of the above muscles are supplied by the femoral nerve. Psoas major is innervated directly by branches of the lumbar plexus which passes through it (L1-L3)

What are the hip abductors and their origin / insertions? Which nerve innervates these muscles?

Gluteus Medius
- Origin: between anterior and posterior gluteal line
- Insertion: lateral surface of greater trochanter
Gluteus Minimus
- Origin: between anterior and inferior gluteal line
- Insertion: anterior surface of greater trochanter (inserts deep to gluteus medius)
Tensor Fascia Lata
- Origin: anterolateral aspect of iliac crest
- Insertion: Iliotibial band

What is the cause of a Trendelenburg gait?

The superior gluteal nerve innervates all of the primary hip abductors above. The hip abductors stabilise the pelvis during walking when the contralateral leg is in the air - preventing the pelvis from dropping. Weakness to abductor mechanism / superior gluteal nerve palsy leads to a Trendelenburg gait

What is the iliotibial band and what is its function?

The iliotibial band is a longitudinal band of fibres that is a reinforcement of the fascia lata

Origin: Anterolateral part of iliac crest
Insertion: Lateral condyle of tibia (Gerdy’s tubercle)
Action: Lateral stabiliser of knee joint in extension - contributes to extension, abduction and external rotation of the femur

Both the gluteus maximus and tensor fascia lata insert onto the iliotibial band. The iliotibial band is important for stability in walking and running - overuse can lead to pain on the lateral aspect of the knee - called iliotibial band syndrome

What is the origin, insertion, action and innervation of gluteus maximus?

Origin: Posterior surface of iliac crest, sacrum and coccyx
Insertion:
- Gluteal Tuberosity (posterior femur) - 25% of muscle fibres inserts here
- Iliotibial band - 75% of muscle fibres insert here
Action: External rotation + extension of hip
Innervation: Inferior gluteal nerve

What are the short external rotators of the hip joint?

The short external rotators can be remembered by "P-GO-GO-Q"

Piriformis
Superior Gemellus
Obturator internus
Inferior Gemellus
Obturator Externus
Quadratus Femoris

What are the deforming forces during a subtrochanteric fracture?

Proximal Fragment
- Abduction - gluteus medius / minimus
- Flexion - Iliopsoas
- External Rotation - short external rotators
Distal Fragment
- Adduction + Shortening - adductor compartment muscles

Neurovascular Structures

Describe the route of the sciatic nerve

The sciatic nerve has both tibial and common peroneal divisions that arise from L4-S3 nerve roots

It leaves the pelvis via the greater sciatic foramen

90% of time exits BELOW piriformis
10% through piriformis
<1% above piriformis

In the gluteal region the sciatic nerve lies beneath gluteus maximus. Running on the posterior surface of quadratus femoris. Its surface landmark is halfway between the ischial tuberosity and greater trochanter of the femur. It then passes down the posterior compartment of the thigh on the posterior surface of adductor magnum. Reaching the popliteal fossa and dividing into the tibial nerve + common peroneal nerve

What muscles does the sciatic nerve supply in the thigh?

Motor

Biceps Femoris
- Long head (tibial division)
- Short head (common peroneal division)
Semi-membranous
Semi-tendinous
Hamstring portion of abductor magnus
All muscles below the knee - via common peroneal and tibial nerves

What sensory areas does the sciatic nerve supply?

Sensory

Posterior aspect of thigh
Lateral aspect of lower leg
Dorsal surface of foot - superficial peroneal nerve
Plantar aspect of foot - medial + lateral plantar nerve (via tibial neve)

What structures exit through the greater sciatic foramen?

The greater sciatic foramen lies between the greater sciatic notch and the sacrospinous ligament. It transmits 10 structures (7 nerves + 3 vessels). The piriformis is a key anatomical landmark for reference

Above Piriformis (2)
- Superior gluteal nerve
- Superior gluteal vessels
Below Piriformis (8)
- Inferior gluteal nerve
- Inferior gluteal vessels
- Pudendal nerve
- Internal pudendal vessels
- Sciatic nerve
- Posterior femoral cutaneous nerve
- Nerve to obturator internus
- Nerve to quadratus femoris