The hip joint Flashcards
what is the lumbosacral joint and what type of joint is it?
The lumbosacral joint is between the lumbar spine and the sacrum of the pelvis, where the vertebral canal ends and the pelvis begins.
It is the located between L5-S1 spinal segments.
This joint is a synovial zygapophyseal joint.
It is a secondary cartilagenous joint; meaning it is permanent and fibrocartilage holds the joints together.
where is the sacroiliac joint and what type of joint is it?
The sacroiliac joint is between the iliac of the pelvis and the sacrum (top part of the tailbone). It connects the outside of the pelvis to the tailbone.
It is a weight-bearing, synovial joint.
what is the pubic symphysis and where is it?
The pubic symphysis is a secondary cartilaginous joint that joins the two pubic bones together above the groin.
It connects one half of the pelvis to the other half anteriorally.
where is the sacrococygeal joint and what type of joint is it?
The sacrococcygeal joint is the connection between the sacrum and the coccyx at the back of the pelvis above the anus in the tailbone.
what are the features of the lumbosacral joint?
- The s-shape of the joint is formed because of the lumbar lordosis ending and the sacral kyphosis starting. The s-shape enables the joint to bear weight.
- the facets of the lumbosacrak joint are antero-laterally oriented and this prevents the lumbar spine sliding forward off the sacrum (prevent anterior shear forces).
What are the features of the sacroiliac joint?
- The sacroiliac joint is between the auricular surface of the sacrum and ilium of the pelvis.
- There are many ligaments around the sacroiliac joint that help it to bear weight (e.g sacrospinous, sacrotuberous, anterior and posterior sacroiliac etc.)
What is nutation and counter nutation of the pelvis?
nutation is when the sacrum is pushed anteriorally and inferiorally into the pelvis in response to increased body weight.
This causes the pelvic outlet (the hole on top of the pelvis) to open, whilst the pelvic inlet (the hole at the bottom of pelvis) closes.
This is because during nutation, the ligaments within the pelvis and sacrum tighten to pull everything in.
Counter nutation is the opposite. When weight is no longer being placed onto the pelvis, the ligaments loosen, releasing the sacrum and causing it to shoot posteriorly and superiorally, back into its original position.
What is the reverse keystone effect with regards to the pelvis and sacrum?
Typically, the keystone effect refers to the effect when a smaller triangular bone acts as a wedge between two larger bones on either side, holding them both up and preventing them from falling apart.
In the case of the pelvis, we see the reverse effect. This is when two iliac bones act as the wedges on either side of the sacrum, holding up the sacrum and keeping the entire pelvis intact.
When weight is applied, the sacrum enters nutation. The forward and downward movement of the sacrum puts it at risk of moving out from between the iliac bones and the entire pelvis falling apart.
To counteract this, there are very strong interosseous sacroiliac ligaments that strap the sacrum to either ilium, so that even during nutation, the sacrum remains partly within the iliac bones to keep the pelvis together.
what are the features of the pubic symphysis?
- the pubic symphysis is a secondary cartilaginous joint.
- There are ligaments that run accross the pubis in a criss-cross motion. This keeps the two pubic halves together.
- There are also the tendons of the adductor muscles and thigh muscles that attach to both halves of the pubis, holding them together.
- the pubis is able to conduct small, gliding movements at the sacroiliac joint.
what are the features of the sacrococcygeal joint?
- It is secondary cartilaginous
- its found at the between the end of the sacrum and the start of the coccyx.
- There are two main ligaments that support this joint; the anterior and superior sacrococcygeal ligaments.
What is the pretzel concept with regards to fractures of the pelvis?
Like breaking a pretzel, it never breaks in only one place. Breaking a pretzel in one place will cause and equal and opposite fracture somewhere else on the pretzel.
Thus, the same rule applies with a pelvic fracture. Whilst it is rare to fracture, if it happens, a fracture on one side will result in an equal fracture on the opposite side of the pelvis.
Alternatively, the whole spine can break off and slip from the pelvis, because the lumbar spine can slip off the sacrum (spondylolysis).
Where is the hip joint and what kind of joint is it?
The hip joint is a synovial ball and socket joint, that involves the head of the femur inserting into the acetabulum of the pelvis.
The acetabular labrum swallows the entire head of the femur, right up until the intertrochanteric line (neck of the femur). This highly stable joint has very restricted mobility, which is the opposite to the shoulder.
The articular surfaces of the joint are covered in hyaline cartilage.
What are the major ligaments of the hip joint?
- Iliofemoral ligaments (ilium to femur)
- Pubofemoral ligaments (pubis to femur)
- Ischiofemoral ligaments (ischium to femur)
- These three joints attach the femoral head to the three different parts of the pelvis that make up the acetabulum. Together, they form a network of ligaments that act like a towel being wrung out, which tightens and becomes stiff during rotation.
- These ligaments act to prevent too much medial/lateral rotation and hip extension/flexion.
What are the accessory articular structures that the hip joint has?
- Acetabular labrum- deepens socket and tightens joint.
- transverse acetabular ligament- fibres with no elastic in them that form a sheet underneath the femoral head within the acetabulum. It prevents inferior displacement of the head of femur.
- ligament of head of femur- literally a string of fibres that come off the tip of the head of femur within the acetabulum. Provides structural support.
- Psoas bursa and trochanteric bursa. Psoas bursa stops friction between the pubfemora ligaments and the psoas muscle that lies directly on top of it. Trochanteric bursa lies between the greater trochanter and the tendons of the gluteal muscles that attach there, to prevent friction.
What direction is the most common for a hip dislocation?
The hip joint is most likely to be dislocated posteriorally, which is most likely to occur with direct trauma to the hip in the sitting position.
Which muscles act as flexors of the hip (contract to flex the hip)?
Psoas and iliacus within the pelvis (together, they form iliopsoas).
Which muscles are responsible for lateral rotation and fixation?
The deep gluteal muscles- piriformis,superior.inferior gemellus, obturator internus, quadratus femoris.
These muscles act like the rotator cuff of the lower limb.
These muscles connect the posterior tailbone to the greater trochanter of the thigh. So contraction pulls the thigh inside out laterally.
These muscles also act to keep the femoral head inside the acetabulum.
