Week 3: Hip Joint & Femur Flashcards
What are the 3 main functions of the hip joint?
- Links the free lower limb to the pelvic girdle
- Allows movement of the hip and therefore the lower limb during weight-bearing activities such as walking
- Predominantly designed for stability, but also allows motion
What is the shape of the articular surface of the head of the femur? And what is the functional relevance of this shape?
- 2/3 of a sphere
- Formation for a ball and socket joint – with the acetabulum
What are the osteokinemtic movements of the hip in the 3 different planes?
- Sagittal: Coronal axis - flexion & extension
- Coronal: Sagittal axis - abduction & adduction
- Transverse: Longitudinal axis - internal & external rotation
What arthrokinematic movements are present at the hip joint?
Glide, spin, roll
Why is the acetabular notch present?
To allow vessels and nerves to enter the acetabulum
Describe the form of the acetabular labrum:
Fibrocartilaginous lip that is attached to the bony rim of the acetabulum
What is the function of the acetabular labrum?
- Increases the extent (surface area) of the acetabular socket
- The femoral head is maintained in the acetabulum even after the capsule and muscle have been severed - largely due to the labrum
What are the 2 intracapsular ligament of the hip joint?
- Transverse acetabular ligament
- Ligamentum teres (ligament of the head)
What is the function of ligamentum teres?
- Connects the femoral head and acetabulum
- The artery to the head of the femur runs along or within the ligament
Describe the morphology of the hip joint capsule:
- Thick fibrous capsule of the hip joint (reinforced by the capsular ligaments)
- Lined with synovial membrane and encloses a voluminous joint cavity containing both the head and neck of femur
What is the proximal attachment of the hip joint capsule?
Bony rim of the acetabulum
Describe the femoral attachment of the hip joint capsule:
Far beyond the articular margins - anteriorly the intertrochanteric line and posteriorly the base of the neck of the femur
On a radiograph of a normal hip joint what fills the apparent joint space?
Articular cartilage, the ligamentum teres and a pad of fat
What are the 3 capsular ligaments of the hip joint capsule and their attachment sites?
- Iliofemoral ligament: AIIS to intertrochanteric line
- Ischiofemoral ligament: Ischial portion of acetabulum superior portion of neck medial to the root of greater trochanter
- Pubofemoral ligament: Pubic part of acetabular rim to neck of femur
Why is the iliofemoral ligament the chief structure that counterbalances gravitational force during relaxed standing?
Because the line of gravitational force falls behind the transverse axis of the hip, the force tends to tilt the pelvis backwards on the femoral heads
- This is resisted by the iliofemoral ligament
In which positions of the hip joint does the iliofemoral ligament become maximally taut?
Extension, external rotation, adduction (superior band)
In which positions of the hip joint does the ischiofemoral ligament become maximally taut?
Extension, internal rotation, abduction
In which positions of the hip joint does the pubofemoral ligament become maximally taut?
Extension, external rotation, abduction
In what position are all 3 capsular ligaments of the hip joint capsule relaxed?
Hip joint flexion
What are the key factors in maintaining stability at the hip joint?
- Deeply molded articular surfaces (femoral head within acetabulum), extended by the labrum
- Strong ligaments and surrounding muscles
- The joint is constructed so that the body weight can be supported on the femoral heads with minimal or no expenditure of muscle energy
Is it easy to dislocate your hip joint?
- No - traumatic dislocation is not common
- May occur in a car-accident (posterior dislocation) or in conjunction with a fracture to the neck of femur as is often seen in elderly people following a fall
Describe the pattern of innervation of the hip joint:
Femoral nerve, obturator nerve, superior gluteal nerve, nerve to quadratus femoris
Describe the arterial supply to the hip joint:
- Medial and lateral circumflex femoral arteries - from deep femoral artery
- Retinacular arteries - branches of the MCFA & LCFA
- Artery to head of femur - branch of obturator artery
What are the clinical implications of a fracture to the neck of the femur?
- Most arteries to the neck and head of femur go through the capsule of the joint at its attachment to the femur and then run proximally along the neck
- Fractures of the neck will often tear the vessels and so hinder healing of the fracture
What is the function of the relationship between the femur and acetabulum?
Important for stability and mobility of the hip joint
What are 2 features of the femoral neck and shaft that are important for function?
- The neck-to-shaft angle (frontal plane)
- The angle of anteversion (transverse plane)
Describe the inclination of the shaft of the femur:
- Inclines downward and inward
- The shaft makes an angle of about 10° with the vertical line dropped from the head of the femur
Why does the femur have this inclination?
- It reflects the greater breadth of the body at the hips than at the knees (larger in women due to wider pelvis)
- The femur is also angled so the condyles are aligned at the knee joint (as the medial condyle projects further distally than lateral)
Where is the neck-to-shaft angle?
Between the axis of the shaft of the femur and the axis of the head and neck
What is the average neck-to-shaft angle in adults?
~135°, but this varies a little between individuals and males/females.
What happens when the angle of inclination decreases (<125 degrees)?
Results in a condition known as coxa vara
What happens when the angle of inclination increases (>125 degrees)?
Results in a condition known as coxa valga
What is the angle of anteversion?
- Refers to the rotation of the neck and head of the femur in relation to the shaft
- Measured in the transverse plane between the axis of the femoral neck and the axis
of the femoral condyles - The angle is approximately 10-15°, but varies between individuals
What happens if the angle of anteversion is greater than 10-15°?
Leads to internal rotation of the lower limb when walking - pigeon-toed
What happens if the angle of anteversion is less than 10-15°?
Retroversion - tendency towards external rotation with gait
On the anterior aspect of the femur, what bony structure runs between, or links the greater and lesser trochanters?
Intertrochanteric line (intertrochanteric crest is on posterior surface of femur)
Where does ossification of the femur occur?
- Shaft
- Head
- Greater trochanter
- Less trochanter
- Distal end
