What type of joint is the hip joint?
Synovial ball and socket joint
What are the articulations of the hip joint?
Head of the femur and the acetabulum of the pelvis
What is the hip joint designed to be? What is sacrificed to achieve this?
A stable, weight bearing joint A large range of movement in exchange for stability is sacrificed to achieve this
What is the acetabulum?
A cup like depression on the lateral side of the pelvis
What are the head of the femur and acetabulum covered in? Where is it thicker?
Both covered in articular cartilage, which is thicker at points of weight bearing
What are the four ligaments that connect thefemur to the pelvis and increase stability?
Ligament of head of femur Pubogemoral ligament Iliofemoral ligament Ischiofemoral ligament
What is the ligament of the head of femur attached to?
The acetabular fossa
What does the ligament of the head of femur enclose?
A branch of the oburator artery which contributes a small proportion of the blood supply to the hip joint
What is A?
The iliofemoral ligament
Where does the iliofemoral ligament attach and what is its function?
The intertrochanteric line Prevents hyperextension of the hip joint
What is B?
What does the pubofemoral ligament prevent?
Excessive abduction and medial rotation
What is C
What does the ischiofemoral ligament prevent?
Excessive medial rotation of the femur at the hip joint
What factors stabilise the hip joint? (4)
The structure of the acetabulum The fibrocartaliginous collar around the acetabulum The iliofemoral, ischiofemoral and pubofemoral ligaments, along with thickened joint capsule Reciprocal support of muscles and ligaments
How does the structure of the acetabulum contribute to stability?
It is deep, and encompasses nearly all of the head of the femur. This decreases the probablity of the head slipping out of the acetabulum, and causing a dislocation.
How does the fibrocartaliginous collar around the acetabulum increase stability?
Increases the depth and articular surface of the acetabulum, and the stability of the joint
How do the iliofemoral, ischiofemoral and pubofemoral ligaments and the thickened joint capsule increase stability?
These ligaments have a unique spiral orientation; this causes them to become tighter when the joint is extended, which adds stability to the joint. Also means less energy is needed to maintain a standing position.
How do muscles and ligaments work in a reciprocal fashion at the hip joint?
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 - the effectively pull the head of the femur into the acetabulum
What movements can occur at hip joint?
flexion, extension, abduction, adduction and medial/lateral rotation
What does the degree to which the hip can flex depend on?
whether the knee is flexed, which relaxes the hamstrings, and increases the range of flexion
What is extension at the hip joint limited by?
The joint capsule, in particular the iliofemoral ligament. The structures become taut during extension to limit further movement
What are the muscles responsible for flexion at the hip?
Iliosoas, rectus femoris, sartorius
What are the muscles responsible for extension at the hip?
Gluteus maximus, semimembranous,semitendinosus and biceps femoris
What are the muscles responsible for abduction at the hip?
Gluteus medius, gluteus minimus and the deep gluteals (piriformis, gemelli etc)
What are the muscles responsible for adduction at the hip?
Adductors longus, brevis and magnus,pectineus and gracillis
What are the muscles responsible for lateral rotation at the hip?
Biceps femoris, gluteus maximus, and the deep gluteals (piriformis, gemelli etc)
What are the muscles responsible for medial rotation at the hip?
Gluteus medius and minimus, semitendinosus and semimembranosus
What does the blood supply to the hip joint come from?
Medial and lateral circumflex femoral arteries Artery to the head of the femur
The disruption of which artery causes avascular necrosis of femoral head and neck and why?
Medial circumflex femoral artery, as it supplies the largest proportion of blood
Why does the lateral circumflex femoral artery supply less blood than the medial?
Has to penetrate through the thick iliofemoral ligament reach hip joint
What is hilton's law?
the nerves supplying the muscles extending directly across and acting at a given joint also innervate the joint
What nerves innervate the hip joint?
Femoral nerve Obturator nerve Nerve to quadratus femoris Superior gluteal nerve
What does the femoral nerve innervate?
: The femoral nerve innervates the flexors of the hip joint, which pass anterior to the hip joint.
What does the obturator nerve innervate?
lateral rotators that pass inferiorly
What does nerve to quadratus femoris innervate
nnervates lateral rotators that pass posteriorly
What does superior gluteal nerve innervate?
Innervates adductor muscles that pass superiorly
Why is the term a "broken hip" often misleading
Because it often refers to a fractured femoral neck
In people below 40 years old, how do femoral neck fractures often occur?
as a result of high energy collisions, with the lower limb extended
In people older than 40, how do femoral neck fractures occur?
Why are women more at risk of femoral neck fractures?
More at risk of osteoporosis in neck of femur
What happens upon a fracture neck of femur?
The affected limb is often laterally rotated. The arteries arising from the medial circumflex femoral artery are usually torn, disrupting the blood supply. This can cause asvascular necrosis of the femoral head and neck.
Outline 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.
Why are hip replacements peformed?
after traumatic injury, or degenerative disease of the joint
What are two types of hip dislocation?
Acquired and congenital
How does a congenital hip dislocation arise?
During development the femoral head is not placed within the acetabulum, resulting in a dislocated joint
What are three common sympotms of a congenital hip dislocation?
inability to abduct at the hip joint - affected limb is shorter - positive Trendelenburg sign
What is trendelenburg sign?
A gait in which during step, instead pelvis being raised on the side of the lifted foot, it drops and pelvis appears to be tilting towards lifted foot. Required flexion at knee on affected side in order for foot to stay clear off the ground
What does congenital hip displacement predispose the patient to?
Arthritis of the hip in later life
Why are aqcuired hip dislocations quite uncommon?
Due to strength and stability of the joint
What are two types of acquired hip dislocation?
Anterior and posterior
Which is the more common type of acquired hip dislocation?
What occurs in an acquired 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. The affected limb becomes shortened and medially rotated.
What nerve is at risk in a posterior hip dislocation?
The sciatic nerve
What occurs if sciatic nerve damaged?
paralysis of the hamstrings, and the muscles distal to the knee
What are anterior hip dislocation a consequence of?
extension, abduction and lateral rotation
What occurs in an anterior hip dislocation?
The femoral head ends up inferior to the acetabulum, and often pulls the acetabular labrum with it.