Musculoskeletal Anatomy - Lower Limb Flashcards
Bones, joints, muscles of the pelvic girdle and lower limb
Why are the bones of the lower limb more massive than those of the upper limb?
They are more massive to support the stress of locomotion and greater weight bearing
Why is the pelvis considered a composite structure?
It contains bones of both the axial (sacrum and coccyx) and the appendicular skeleton (hip bones).
Which 3 bones make up each pelvic (aka coxal, innominate, or hip) bone? What cartilage separates them as children?
Ileum, ischium, and pubis. Separated by hyaline cartilage
What differences between the male and female pelvis allow childbirth?
A female pelvis has:
- broader pubic arch, with the angle inferior to the pubic bones generally being greater than 90 degrees
- an enlarged pelvic outlet
- less curvature on the sacrum and coccyx
- wider, more circular pelvic inlet
- relatively broad, low pelvis
- ilia that project more laterally than in the male pelvis
Fully classify the joint between the two pubic bones of the pelvis
Amphiarthrotic cartilaginous symphysis joint
What are 3 functions of the patella
1) strengthen quadriceps tendon
2) protect anterior surface of knee joint
3) serve as anatomical pulley that increases contraction force of quadriceps femoris
Why is the fibula smaller and thinner than other leg bones?
It bears minimal body weight (maybe 10%)
What bony structures make up the ball of the foot?
The phalanges and metatarsal bones
Why does it make sense for the pubic symphysis joint to be partially moveable
Childbirth - the baby’s head and body have to fit through
Fully classify the sacroiliac joint. What cartilage covers the articulating surfaces?
- Diarthrotic synovial multiaxial planar joint
- Hyaline cartilage
Which joint is a common site of lower back pain?
The sacroiliac joint
Fully classify the hip joint and list the movements allowed
Diarthrotic synovial triaxial ball and socket joint
Adduction, abduction, flexion, extension, circumduction, rotation
What are the functions of the medial and lateral menisci of the knee?
1) Act as cushions
2) conform to the shape of articulating surfaces as femur changes position
3) increase surface area of tibiofemoral joint
4) provide lateral stability to the joint
What are the functions of the anterior and posterior cruciate ligaments?
1) limit anterior and posterior movement of femur
2) maintain alignment of femoral and tibial condyles
What is the function of the medial and lateral collateral ligaments and when are they the tightest?
reinforce medial and lateral surfaces of the knee. Tightest when knee is in extension
Fully classify the tibiofemoral joint and list the movements allowed:
- diarthrotic synovial monaxial hinge joint
- flexion, extension, some rotation
Fully classify the talocrural joint and state which movements are allowed:
Diarthrotic synovial monaxial hinge joint
Allows dorsiflexion and plantarflexion.
Fully classify the proximal, middle, and distal tibiofibular joints
Proximal: diarthrotic synovial multiaxial planar joint
Middle: amphiarthrotic fibrous syndesmosis joint
Distal: partial diarthrotic synovial multiaxial planar, partial amphiarthrotic fibrous syndesmosis.
What type of bone is the patella?
Sesamoid
Which two major connective tissues (tendon and ligament) attach at the patella?
- patellar ligament
- quadriceps tendon
Why is it difficult to walk if you fracture your fibula even though it is not part of the knee joint?
The fibula is a site of attachment for many muscles, so when it is broken the muscles cannot attach properly and therefore cannot function properly. The fibula also helps to stabilize the ankle joint.
What is the function of the sacroiliac joint?
To dissipate the load of the torso and pelvis
Approximately how much of the femoral head fits into the acetabulum? What else helps to stabilize this structure?
- approximately 50% of the head
- four broad ligaments: ischiofemoral, iliofemoral, pubofemoral, and transverse acetabular ligaments. The ischio-, ilio-, and pubofemoral ligaments are all regional thickenings of the capsule
The articulate capsule is further deepened by the ___________. This helps stabilize the head in the acetabulum.
- acetabular labrum
What are the two anterior ligaments of the hip joint? In what position are they the most taut?
- pubofemoral and iliofemoral ligaments
- most taut in extension and abduction
Which is the posterior ligament in this capsule? What movement does this ligament limit?
- ischiofemoral ligament
- limits extension and internal (medial) rotation
What is the role of the ligament of the head of the femur?
- minimal role in joint stabilization
- tenses when thigh is flexed and undergoing external rotation
- location of blood vessels to head of the femur
Why are hip dislocations relatively uncommon and what tends to occur instead?
- the head of the femur is enclosed by an almost complete bony socket, a strong articulate capsule, and is surrounded by stout supporting ligaments and dense muscular padding to make it a very stable joint.
- fractures of the femoral neck are more common than hip dislocations
What type of hip dislocation is most common?
- posterior hip dislocation
Why is the knee not a very stable joint compared to the hip?
The hip has lots of muscle mass as well as bone on bone articulation to keep the femur in the socket of the acetabulum. The knee has some support from ligaments and muscles but not to the same extent as the hip
Which joint allows the largest range of motion of the lower limb?
The knee - up to 160 degrees
Fully classify the patellofemoral joint and list the movement(s) allowed:
Diarthrotic synovial multiaxial planar joint. Allows gliding motion
What is the purpose of the fat pads and bursae in the knee joint?
Provide padding around the margins of the knee and reduce friction between the patella and other tissue.
What movements do the medial, lateral, anterior, and posterior ligaments of the knee (respectively) limit?
Medial: limits medial displacement of the tibia relative to the femur
Lateral: limits lateral displacement of the tibia relative to the femur
Anterior: limits anterior displacement of the tibia relative to the femur.
Posterior: limits posterior displacement of the tibia relative to the femur.
When is the ACL tightest? When is the PCL tightest?
ACL: when knee is in extension
PCL: when knee is in flexion
Which ligament is most commonly injured and why?
ACL is more commonly injured because we spend more time standing with our knee in extension.
How do ACL injuries occur and how can we prevent them?
Generally occur in high contact sports due to contact when the foot is planted and there is an impact from the side or when there is a sudden change in direction, sudden deceleration, or awkward landing. These injuries can be prevented by keeping some flexion in the knee so that the ACL is not stretched as extensively.
What is the function of the two popliteal ligaments?
to reinforce the back of the knee joint
How does the knee lock and why does it do this?
The knee locks in extended position when slight lateral rotation of the tibia tightens the ACL and jams the meniscus between the tibia and femur. The knee locks to allow us to stand for prolonged periods of time without using and tiring the extensor muscles.
How does the knee unlock?
Contraction of the popliteal muscle initiates slight medial rotation of the tibia to begin flexion of the knee.
In which position do most ankle injuries occur and why?
Most ankle injuries are due to an excessive amount of inversion during plantar flexion (rolling the ankle). This position uses more of the range of motion of our ankle but this leads to the tradeoff of a loss of stability in the joint. This most often causes damage to the lateral ligaments of the ankle.
Which articulation of the ankle is the primary site for weight bearing?
The tibiotalar joint
Which 3 joints provide medial and lateral stability at the ankle?
1) proximal tibiofibular joint
2) distal tibiofibular joint
3) fibulotalar joint
What is the function of the tibiofibular ligaments?
- primary stabilizer of the ankle
- limit external rotation of the foot and sital fibular motion on the tibia
What is the primary function of the lateral ligaments?
- limit anterior or posterior displacement of the talus and resist inversion
Which ligaments of the ankle are most commonly sprained?
The anterior talofibular ligament is most commonly sprained. When in plantar flexion, this ligament is most taut and therefore most vulnerable.
What is the main function of the deltoid ligament of the ankle?
Reinforce the ankle joint and help resist eversion
