Hip Joint Flashcards
What kind of joint is the hip?
Ball and socket synovial type joint
What is the hip joint between?
The head of the femur and acetabulum of the pelvis
What does the hip joint join?
The lower limb to the pelvic girdle
What is the hip joint designed to be?
A stable weight bearing joint
What is the result of the hip being a stable weight bearing joint?
A large range of movement is sacrificed for stability
What does the hip joint consist of?
An articulation between the head of the femur and the acetabulum of the pelvis
What is the acetabulum?
A cup-like depression in the lateral side of the pelvis
What shape is the head of the femur?
Hemispherical
How does the head of the femur fit into the acetabulum?
Fits completely into the concavity
What are the acetabular and head of femur covered in?
Articular cartilage
Where is the articular cartilage on the acetabulum and head of femur thicker?
At places of weight bearing
What do the ligaments of the hip joint act to do?
Increase stability
How can the ligaments of the hip joint be divided?
Into two groups, intracapsular and extracapsular
What is the intracapsular ligament?
The ligament of the head of the femur
Where does the ligament of the head of the femur run?
From the acetabular fossa to the fovea of the femur
What does the ligament of the head of the femur enclose?
A branch of the obturator artery
What does the branch of the obturator artery comprise?
A small proportion of the hip joint blood
What are the extracapsular ligaments?
Iliofemoral
Pubofemoral
Ischiofemoral
What are the extracapsular ligaments continuous with?
The outer surface of the hip joint capsule
Where is the iliofemoral ligament located?
Anteriorly
What does the iliofemoral ligament originate from?
The ilium, immediately inferior to the anterior inferior iliac spine
Where does the iliofemoral ligament attach?
To the intertrochanteric line in two places
What does the attachment of the iliofemoral ligament give?
The Y shaped appearance of the ligament
What does the iliofemoral ligament prevent?
Hyperextension of the hip joint
Where is the pubofemoral ligament located?
Anteriorly and inferiorly
Where does the pubofemoral ligament attach?
At the pelvis, to the iliopubic eminance and obturator membrane
What does the pubofemoral ligament blend with?
The articular capsule
What does the pubofemoral ligament do?
Prevents excessive abduction and extension
Where is the ischiofemoral ligament located?
Posteriorly
Where does the ischiofemoral ligament originate from?
The ischium of the pelvis
What does the ischiofemoral ligament attach to?
The greater trochanter of the femur
What does the ischiofemoral ligament prevent?
Excessive extension of the femur at the hip joint
How is vascular supply to the hip joint achieved?
Via the medial and lateral circumflex femoral arteries, and the artery to the head of the femur
What are the circumflex arteries branches of?
The profunda femoris artery
Where do the circumflex arteries anastomose?
At the base of the femoral neck
What is formed when the circumflex arteries anastomose?
A ring, from which smaller arteries arise to supply the joint itself
What is responsible for the majority of the arterial supply to the hip joint?
The medial circumflex femoral artery
Why is it the medial, rather than lateral, circumflex femoral artery that provides the majority of the arterial supply to the hip joint?
The lateral circumflex femoral artery has to penetrate through the thick iliofemoral ligament to reach the hip joint
What can damage to the medial circumflex artery result in?
Avascular necrosis of the femoral head
What is the hip joint innervated by?
The femoral nerve, the obturator nerve, superior gluteal nerve, and the nerve to the quadratus femoris
What is the primary function of the hip?
To bear weight
What structures increase the stability of the hip joint?
Acetabulum
Acetabular labrum
Ligaments
Muscles
How does the acetabulum of the hip increase its stability?
It is deep, encompasses nearly all of the head of the femur, decreasing the probability of the head slipping out of the acetabulum and causing dislocation
What is the acetabular labrum?
The fibrocartilaginous collar around the acetabulum
What does the acetabular labrum do?
Increases its depth
What does the increase in depth produced by the acetabular labrum do?
Provides a large articular surface, thus improving the stability of the joint
What ligaments stabilise the hip joint?
Iliofemoral, pubofemoral and ischiofemoral
What do the hip ligaments stabilise the joint in conjunction with?
The thickened joint capsule
What features of the ligament contribute to their role of strengthening the hip?
Very strong
Spiral orientation
What is the result of the spiral orientation of the ligaments stabilising the hip?
It causes them to become tighter when the joint is extended, which adds stability to the joint and means less energy is needed to maintain a standing position
How do muscles and ligaments work at the hip joint?
In a reciprocal fashion
How do the muscles and ligaments of the hip joint work anteriorly?
Here the ligaments are strongest, and the medial flexors (located anteriorly) are fewer and weaker
How do the muscles and ligaments of the hip joint work posteriorly?
Here the ligaments are weakest, and the medial rotators are greater and stronger- they effectively ‘pull’ the head of the femur into the acetabulum
What movements can be carried out at the hip?
Flexion Extension Abduction Adduction Medial/lateral rotation
What does the degree to which flexion at the hip can occur depend on?
Whether the knee is flexed
Why does hip flexion depend on knee flexion?
Because knee flexion releases the hamstrings, and so increases the range of flexion
What is extension at the hip joint limited by?
The joint capsule and, in particular, the iliofemoral ligament
How do the joint capsule and iliofemoral ligament limit hip extension?
They become taut during extension to limit further movement
What produces flexion at the hip?
Iliosoas
Rectus femoris
Sartorius
What produces extension at the hip?
Gluteus maximus
Semimembranosus
Semitendinosus
Biceps femoris
What produces abduction at the hip?
Gluteus medius
Gluteus minimis
Deep gluteals (piriformis, gemelli etc)
What produces adduction at the hip?
Adductors longus, brevis and magnus, pectineus and gracillis
What produces lateral rotation at the hip?
Biceps femoris
Gluteus maximus
Deep gluteals (piriformis, gemelli etc)
What produces medial rotation at the hip?
Gluteus medius and minimus
Semitendinosus
Semimembranosus
How do fractures to the neck of the femur occur?
In 40 year olds, more likely to occur from balls
Who are fractures to the neck of the femur more likely to occur in?
Women
Why are fractures to the femoral neck more likely to occur in women?
They generally have more brittle necks from osteoporosis
What often happens to the affected limb in a femoral neck fracture?
It is often laterally rotated
The arteries arising from the medial circumflex artery are usually torn, disrupting the blood supply
What can the disruption of the blood supply in femoral neck fractures cause?
Avascular necrosis of the femoral head and neck
What happens in a surgical hip replacement?
A plastic socket is cemented to the hip bone to replace the acetabulum, while a stainless steel femoral stem and head replaces the femur
When are hip replacements usually performed?
After traumatic injury or in degenerative disease of the joint
What are the types of hip dislocation?
Acquired and congenital
Who is congenital dislocation of the hip joint more common in?
Girls (8x more likely)
How common is congenital dislocation of the hips?
Relatively common
What causes congenital dislocation of the hip?
During development, the femoral head is not placed within the acetabulum, resulting in a dislocated joint
What are the common symptoms of congenital hip dislocation?
Inability to abduct at the hip joint
Affected limb is shorter
Positive Trendelenburg sign
What does having congenital displacement of the hip predispose to?
Arthritis of the hip later in life
How common are acquired dislocations of the hip joint?
Quite uncommon
Why are acquired dislocations of the hip joint quite uncommon?
Because of the strength and stability of the joint
What are acquired dislocations of the hip usually due to?
Traumatic accidents
What are the types of acquired hip dislocation?
Posterior and anterior
What is the more common type of acquired hip dislocation?
Posterior
What happens in a posterior hip dislocation?
The femoral head is forced posteriorly (backwards), and tears through the inferior and posterior part of the joint capsule, where it is at its weakest
What are the signs of a posterior hip dislocation?
The limb becomes shortened and medially rotated
What can be damaged in a posterior hip dislocation?
The sciatic nerve
Why can the sciatic nerve be damaged in a posterior hip dislocation?
Because it runs posteriorly to the hip joint
What would sciatic nerve damage cause?
Paralysis of hamstrings, and muscles distal to the knee
What are anterior hip dislocations a consequence of?
Extension, abduction and lateral rotation
What is the result of an anterior hip dislocation?
The femoral head ends up anterior and inferior to the acetabulum, and often pulls the acetabular labrum with it
