The Hip Joint Flashcards
What type of joint is the Hip Joint?
A ball and socket synovial joint
What are the articulations of the hip joint?
The hip joint is formed by an articulation between the pelvic acetabulum and the head of femur
What is the Hip Joint designed for?
It’s a connection from the lower limb to the pelvic girdle, and thus is designed for stability and weight-bearing rather than a large range of movement
What is the acetabulum?
A cup-like depression located on the inferolateral aspect of the pelvis. Its cavity is deepened by the presence of a fibrocartilaginous collar called the acetabular labrum.
The head of femur is hemispherical, and fits completely into the concavity of the acetabulum.
Both the acetabulum and head of femur are covered in articular cartilage, which is thicker at the places of weight bearing.
What are the two groups in which the ligaments of the hip can be divided in to?
Intracapsular
Extracapsular
Name the intracapsular ligaments of the hip joint
The only intracapsular ligament is the ligament of head of femur. It’s a relatively small structure, which runs from the acetabular fossa to the fovea of the femur.
It encloses a branch of the obturator artery (artery to head of femur), a minor source of arterial supply to the hip joint.
Name the extracapsular ligaments of the hip joint
There are three main extracapsular ligaments, continuous with the outer surface of the hip joint capsule:
- Iliofemoral ligament - spans between the anterior inferior iliac spine and the intertrochanteric line of the femur. It has a Y shaped appearance and prevents hyperextension of the hip joint
- Pubofemoral - spans between the superior pubic rami and the intertrochanteric line of the femur. It has a triangular shape and prevents excessive abduction and extension
- Ischiofemoral - spans between the body of the ischium and the greater trochanter of the femur. It has a spiral orientation and prevents excessive extension
Describe the vascular supply of the hip joint
The arterial supply to the hip joint is largely via the medial and lateral circumflex femoral arteries - branches of the deep femoral artery. They anastomose at the base of the femoral neck to form a ring, from which smaller arteries arise to supply the hip joint itself.
The artery to head of femur and the superior/inferior gluteal arteries provide some additional supply.
Which of the circumflex femoral arteries is responsible for the majority of the arterial supply?
The medial circumflex femoral artery is responsible for the majority of the arterial supply (the lateral circumflex femoral artery has to penetrate through the thick iliofemoral ligament). Damage to the medial circumflex femoral artery can result in avascular necrosis of the femoral head.
Describe the nerve supply to the hip joint
The hip joint is innervated by the femoral nerve, obturator nerve, superior gluteal nerve and nerve to quadratus femoris
What are the stabilising factors of the hip joint?
The primary function of the hip joint is to weight-bear. There are a number of factors that act to increase stability of the joint.
The first structure is the acetabulum. It’s deep and encompasses nearly all of the head of the femur. This decreases the probability of the head slipping out of the acetabulum (dislocation).
The acetabular labrum increases the depth of the acetabulum, providing a larger articular surface, further improving stability of the joint.
The iliofemoral, pubofemoral and ischiofemoral ligaments are very strong, and along with the thickened joint capsule, provide a large degree of stability. These ligaments have a unique spiral orientation; this causes them to become tighter when the joint is extended.
The muscles and ligaments work in a reciprocal fashion, anteriorly where the ligaments are strongest, the medial flexors (located anteriorly) are fewer and weaker. Posteriorly, where the ligaments are weakest, the medial rotators are greater in number and stronger - they effectively pull the head of the femur into the acetabulum.
