Module 9: Biomechanics of the Lower Extremity Flashcards
Name the bones that form the pelvic girdle.
Sacrum, ilium, pubis, ischium
Name the bones that form the lower limb.
Femur, patella, tibia, fibula, tarsals, metatarsals, phalanges
What are the functions of the pelvic girdle?
Support the body (weight bearing/posture)
Allow for locomotion
Name the joints of the pelvic girdle.
Sacroiliac joint and symphysis pubis
Name the axis and planes of movement that are possible in the hip joint.
Anteroposterior axis | Frontal plane | Abduction/adduction
Frontal axis | Sagittal plane | Flexion/extension
Vertical axis | Transverse plane | Rotation/circumduction
What type of joint is the pubic symphysis?
Cartilaginous, amphiarthrosis, little to no movement
What type of joint is the sacroiliac joint?
Synovial plane joint
Describe the movement of nutation of sacrum and when it occurs
A forward tilt of the sacral base with the apex moving posteriorly, occurring during lumbar flexion and weight-bearing activities
Describe the movement of counternutation of the sacrum and when it occurs.
A backward tilt of the sacral base with the apex moving forward, occurring during lumbar extension and hip extension.
What are the pelvic movements?
The pelvic girdle moves as a unit to facilitate the positioning and function of the hip joint and vertebrae. Movements include anterior and posterior pelvic tilts
Describe the movement of anterior pelvic tilt and which muscles are responsible for this movement.
The ASIS moves downward and the PSIS moves upward. This movement is produced by the hip flexors (iliopsoas = iliacus + psoas)
Describe the movement of posterior pelvic tilt and which muscles are responsible for this movement?
The ASIS moves upward and the PSIS moves downward. This movement is produced by the hip extensors (gluteus maximus)
List 2 differences between the hip and shoulder joint that impact the stability of the joints.
The hip joint has a deeper socket (acetabulum) enhancing stability
The femoral head has more contact with its acetabulum (~70%), while the shoulder has less, enhancing mobility
List 2 similarities between the hip and shoulder joint.
Both have a labrum (fibrocartilage that deepens the joint socket) and gravity aids in coaptation, or stability, especially when upright
What is the function of the labrum in the hip joint?
Increase joint congruency, stabilizing the hip by providing a more secure fit for the femoral head within the acetabulum.
What effect does unilateral movement of the lower limb in the sagittal plane have on the pelvis?
Causes pelvic rotation towards the stepping leg to facilitate fluid and balanced walking
What effect does bilateral movement of the lower limbs in the sagittal plane have on the pelvis?
Aids in pelvic stabilization during symmetrical lower limb movements (squatting)
Which muscle is the primary abductor of the thigh?
Gluteus medius and gluteus minimus
Which joint of the lower limb is most susceptible to injuries and why?
The knee joint due to high mechanical demands and a heavy reliance on soft tissue
How many degrees of freedom does the knee joint have?
Two: flexion/extension and minimal rotation (screw-home mechanism) to lock in
What is the patellofemoral joint?
The joint between the patella and the femur.
What structure is found on the knee joint that helps to increase congruency between the femur and the tibia?
The meniscus
How many degrees of freedom does the ankle joint have?
Two in total from the:
Subtalar joint for inversion / eversion
Talocrural joint for dorsiflexion / plantarflexion
Name the tarsal bones.
Calcaneus, navicular, talus, cuboid, and the medial, intermediate and lateral cuneiforms
What is the angle of inclination of the femur?
The angle (~125*) formed by the neck and shaft of the femur.
What happens if the femoral angle of inclination exceeds 125*?
Coxa valga: the femoral neck becomes more vertical, lengthening the limb, reducing hip abductor efficiency, increasing joint compression, and impairing muscle function and stability. This affects posture, movement, and may lead to compensatory adjustments in the lower limb.
What happens if the femoral angle of inclination is less than 125*?
Coxa vara: The angle between the femoral neck and shaft decreases, making the femoral neck more horizontal. This shortens the limb, improves hip abductor efficiency, increases shear forces on the femoral neck, and changes muscle alignment, affecting walking, posture, and causing compensatory adjustments in the lower limb.
What is the angle of anteversion of the femur?
The degree of forward rotation (~14*) of the femoral neck relative to the shaft in the transverse plane
What happens if the angle of anteversion of the femur is greater than 14 degrees?
It results in internal rotation (anteversion) of the femur (toeing in)
What happens if the angle of anteversion of the femur is less than 14 degrees?
It results in external rotation (retroversion) of the femur (toeing out)
What is the definition of the Q-angle?
The angle formed between the line connecting the ASIS to the patella and the line from the patella to the tibial tuberosity.
What happens if the Q-angle is greater than 15 degrees?
Suggests genu valgum (knock-knees)
What happens if the Q-angle is less than 15 degrees?
Suggests genu varum (bowlegs)
Name the 3 arches of the foot.
Lateral longitudinal, medial longitudinal, anterior transverse
Give 2 strengthening exercises for the quadriceps in a closed kinetic chain and 1 exercise for the same in an open kinetic chain.
CKC – Step ups and lunges
OKC - Knee extensions
What is the definition of pes cavus?
A higher-than-normal arch of the foot
What is the definition of pes planus?
The foot has little to no arch, resulting in a flat foot.
During the movement of sitting to stand, what needs to happen to the COG?
COG must shift forward during the transition from sitting to standing.
During the movement of sitting to stand, when is the movement of greatest torque on the knee joint?
Occurs immediately after lifting off from a chair.
Which muscles are mostly active during the movement of sitting to stand?
The quadriceps and the hip extensors.
