Hip Joint Anatomy is a ball and socket joint that is the point of articulation between the head of the femur and the acetabulum of the pelvis. The joint is a diarthrodial joint with its inherent stability dictated primarily by its osseous components/articulations. The primary function of the hip joint is to provide dynamic support the weight of the body/trunk while facilitating force and load transmission from the axial skeleton to the lower extremities, allowing mobility.[rx][rx][rx]
The hip joint is primarily responsible for providing dynamic support of the weight of the upper body while facilitating force and load transmission from the axial skeleton to the lower extremities. This structure and function allow for ambulation and mobility. It is a ball-and-socket synovial joint that articulates the head of the femur with the acetabulum of the pelvis.
Hip Joint Anatomy
The hip acts as a multi-axial, ball-and-socket joint upon which the upper body is balanced during stance and gait. The balance and stability provided by the hip joint allow motion while supporting forces encountered during daily activities. The congruity of the femoral head with the acetabulum allows the rotational motion required to perform these tasks without any detectable translational motion which would destabilize the joint and increase the risk of dislocation. The inherent stability provided by the osseous anatomy of the joint coupled with the stabilizing forces of the fibrous capsule and neuromuscular anatomy defines the absolute limits of motion of the hip joint before the occurrence of bony impingement.
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Flexion – 120 degrees
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Extension – 10 degrees
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Abduction – 45 degrees
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Adduction – 25 degrees
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Internal Rotation – 15 degrees
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External rotation – 35 degrees
Ischiofemoral ligament – It attaches to the posterior surface of the acetabular rim and labrum and courses circumferentially around the joint to its insertion on the anterior aspect of the femur. The ischiofemoral ligament limits internal rotation and hip adduction with flexion.
Iliofemoral ligament (Y Ligament of Bigelow) – It is a triangle-shaped ligament that attaches along the intertrochanteric line of the femur and converges into its attachment on the anterior inferior iliac spine (AIIS). This is the strongest ligament in the body. The iliofemoral ligament limits extension and external rotation of the hip and assists in the maintenance of a static erect posture with minimal muscular activity[rx] [rx],[rx]
Pubofemoral ligament – Located on the anterior aspect of the hip joint, this ligament extends from the anterior portion of the pubic ramus to the anterior surface of the intertrochanteric fossa often blending with the inferior fibers of the iliofemoral ligament. The pubofemoral ligament limits hip abduction and extension.
Zona orbicularis (annular ligament) – Not visible externally, it encircles the femoral neck like a buttonhole and acts as a biomechanical locking ring wrapped around the femoral neck. The zona orbicular forms a locking ring around the femur which resists distraction forces on the hip.
Ligamentum teres – Located deep in the hip, it has a pyramidal shape with a broad origin from nearly the entire transverse acetabular ligament attaching to the ischial and pubic bases by two bundles, with the posterior bundle being stronger than the anterior bundle. The ligamentum teres’ function prior to puberty has been well-described as it provides a secondary blood supply to the head of the femur. [rx]
Acetabular labrum – This is a fibrocartilaginous rim, composed of circumferential collagen fibers, that spans the entirety of the acetabulum and is continuous with the transverse acetabular ligament. The labrum contributes approximately 22% of the articulating surface of the hip and increases the volume of the acetabulum by 33%. The acetabular labrum limits the extreme range of motion and deepens acetabulum to assist in the dissipation of the large forces across the hip with a stride in athletic activities. It also provides a sealing rim around the joint, enabling increased hydrostatic fluid pressure to facilitate synovial lubrication and resistance to joint distraction. [rx]
Nerves Supply of Hip Joint
- Obturator nerve – Originates from nerve roots L2-L4 and exits through the obturator canal before splitting into an anterior division that runs anterior to obturator externus and a posterior division which runs posterior to obturator externus. The obturator nerve supplies sensory innervation to the inferomedial thigh via the cutaneous branch of the obturator nerve and motor innervation to gracilis (anterior division), adductor longus (anterior division), adductor brevis (anterior/posterior divisions), and adductor Magnus (posterior division).
- Genitofemoral nerve – Originates from nerve roots L1-L2. It pierces the psoas muscle and continues down the anteromedial surface of psoas before dividing into femoral and genital branches. The femoral branch provides sensory innervation to the proximal anterior thigh over the femoral triangle. The genital branch provides sensory innervation to the scrotum/labia. It has no motor function.
- Lateral femoral cutaneous nerve – Originates from nerve roots L2-L3. Crosses inferior to the anterior superior iliac spine (ASIS) and provides sensory innervation to the lateral thigh. It has no motor function. Iatrogenic injury can occur during hip arthroplasty utilizing an anterior approach or when placing the anterior portal for hip arthroscopy.
- The femoral nerve – originates from nerve roots (L2-L4). It lies between the psoas major and iliacus and branches in the femoral triangle. The femoral nerve provides sensory innervation to the anteromedial thigh via anterior cutaneous branches and motor innervation to the psoas, pectineus, Sartorius, quadriceps (rectus femoris, vastus lateralis, vastus intermedius, vastus medialis).
- Sciatic nerve – originates from the sacral plexus and projects through the greater sciatic foramen descending down the posterior thigh deep to the hamstrings and superficial to adductor Magnus. The sciatic nerve has two distinct divisions: tibial division and common peroneal division. The tibial division originates from nerve roots L4-S3 and provides motor innervation to biceps femoris (long head), semitendinosus, and semimembranosus. There is no sensory innervation in the thigh. The common peroneal division originates from nerve roots L4-L2 and provides motor innervation to biceps femoris (short head).
- Posterior femoral cutaneous nerve – Originates from nerve roots S1-S3 and passes through the greater sciatic foramen medial to the sciatic nerve. The posterior femoral cutaneous nerve provides sensory innervation to the posterior thigh and has no motor function.
Blood Supply of Hip Joint
The arterial blood supply of the hip joint is complex and comes from multiple sources. The following list includes the branches of the anterior trunk of the internal iliac artery:
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Obturator artery
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Umbilical artery, which branches to form the superior vesical artery
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Inferior vesical artery
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Vaginal artery (female)
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Uterine artery (female)
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Middle rectal artery
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Internal pudendal artery
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Inferior gluteal artery
The following list includes the branches of the posterior trunk of the internal iliac artery
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Superior gluteal artery
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Lateral sacral arteries
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Iliolumbar artery
Most of the arteries of the hip region originate from the external iliac artery and include
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Femoral artery
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Superficial circumflex iliac artery
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External pudendal artery
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Superficial femoral artery
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Profunda femoral artery (the deep artery of the thigh)
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Lateral femoral circumflex artery
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Medial femoral circumflex artery
Muscles Attachment of Hip Joint
Understanding the synchronization of muscle contractions that facilitate balanced gait is critical when evaluating pathology of the hip’s articular surface.
Hip Flexors
Psoas major
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Origin: T12-L5 vertebrae
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Insertion: Lesser trochanter
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Innervation: Femoral nerve
Psoas minor (present in 50% of the population)
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Origin: T12-L1 vertebrae
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Insertion: Iliopubic eminence
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Innervation: L1 ventral ramus
Pectineus (flexes and adducts thigh)
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Origin: Pectineal line of pubis
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Insertion: Pectineal line of femur
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Innervation: Femoral nerve
Iliacus
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Origin: Iliac fossa/ Sacral ala
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Insertion: Lesser trochanter
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Innervation: Femoral nerve
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Hip Extensors and External Rotators-
Gluteus maximus
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Origin: Ilium, dorsal sacrum
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Insertion: ITB, gluteal tuberosity
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Innervation: Inferior gluteal nerve
Obturator externus
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Origin: Ischiopubic rami, obturator membrane
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Insertion: Trochanteric fossa
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Innervation: Obturator nerve
Short External Rotators
Piriformis
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Origin: Anterior sacrum
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Insertion: Superior greater trochanter
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Innervation: Nerve to Piriformis (S2, posterior division of lumbosacral plexus)
Superior gemellus
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Origin: Ischial spine
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Insertion: Medial greater trochanter
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Innervation: Nerve to obturator internus (L5-S2, anterior division of lumbosacral plexus)
Obturator internus
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Origin: Ischiopubic rami, obturator membrane
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Insertion: Medial greater trochanter
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Innervation: Nerve to obturator internus (L5-S2, anterior division of lumbosacral plexus)
Inferior gemellus
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Origin: Ischial tuberosity
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Insertion: Medial greater trochanter
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Innervation: Nerve to quadratus femoris (L4-S1, anterior division of lumbosacral plexus)
Quadratus femoris
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Origin: Ischial tuberosity
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Insertion: Intertrochanteric crest
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Innervation: Nerve to quadratus femoris (L4-S1, anterior division of lumbosacral plexus)
Hip Abductors
Tensor fascia latae
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Origin: Iliac crest, ASIS
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Insertion: Iliotibial band/proximal tibia
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Innervation: Superior gluteal nerve
Gluteus medius
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Origin: Ilium between anterior and posterior gluteal lines
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Insertion: Greater trochanter
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Innervation: Superior gluteal nerve
Gluteus minimus
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Origin: Ilium between anterior and posterior gluteal lines
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Insertion: Greater trochanter
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Innervation: Superior gluteal nerve
Hip Adductors
Adductor magnus
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Origin: Pubic ramus, ischial tuberosity
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Insertion: Linea aspera, adductor tubercle
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Innervation: Obturator nerve, sciatic nerve
Adductor longus
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Origin: Body of pubis
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Insertion: Linea aspera
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Innervation: Obturator nerve
Adductor brevis
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Origin: Body and inferior pubic ramus
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Insertion: Pectineal line, linea aspera
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Innervation: Obturator nerve
Gracilis
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Origin: Body and inferior pubic ramus
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Insertion: Proximal medial tibia (pes anserinus)
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Innervation: Obturator nerve
Movement of Hip Joint Anatomy
Muscles of the hip joint can be grouped based upon their functions relative to the movements of the hip.[rx]
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Flexion – Primarily accomplished via the psoas major and the iliacus, with some assistance from the pectineus, rectus femoris, and the sartorius.
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Extension – Primarily accomplished via the gluteus maximus as well as the hamstring muscles.
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Medial rotation – Primarily accomplished by the tensor fascia latae and fibers of the gluteus medius and minimus.
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Lateral rotation – Primarily accomplished by the obturator muscles, the quadratus femoris, and the Gemelli with assistance from the gluteus maximus, sartorius, and piriformis.
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Adduction – Primarily accomplished by the adductor longus, brevis, and magnus with assistance from the gracilis and pectineus
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Abduction – Primarily accomplished by the gluteus medius and minimus with assistance from the tensor fascia latae and sartorius.
References
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Adductor Brevis Muscle – Origin, Nerve Supply, Function
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Peroneus Tertius Muscle – Anatomy, Nerve Supply, Function
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