Lecture 12: MSK 3 Flashcards
General function of lower extremity
Responsible for stability (posture) and locomotion
Concentric and Eccentric (muscles shorten and lengthen)
Three regions of lower extremity
Pelvic region: between iliac crest and gluteal fold
Thigh: between hip and knee
Lower leg: below the knee
How are bones arranged in pelvic girdle?
Bones form a complete ring: basin
See figure
Role of pelvic girdle
Weight bearing
Bipedal movement (upright walking)
Protects reproductive organs
What is the hip bone composed of?
aka innominate bone
Three bones that fuse together (Y shape in acetabulum)
Ilium
Ischium
Pubis
See figure
Ilium (shape, location, role)
Large fan shape
Makes up proximal portion of innominate bone
Protects lower abdominal contents
Provides surface area for attachment of large powerful muscles
Ischium location
Posterior and inferior aspect of innominate bone
Pubis location
Anterior/inferior aspect of the innominate bone
Where is the sacroiliac joint?
Between the auricular surface of the ilium and the auricular surface of the sacrum
See figure
Sacroiliac joint type
Partly synovial (anterior)
Partly fibrous (posterior)
Movement allowed by sacroiliac joint
Some flexion/extension
Important in walking and full forward flexion
How is the sacroiliac joint supported?
Very strong ligaments
- Sacroiliac ligaments (ant/post)
- Sacrospinous ligament
- Sacrotuberous ligament
Where is the symphysis pubis?
Point where the two pubic bodies join anteriorly
See figure
How are the pubic bones joined?
Two very strong ligaments superiorly and inferiorly
Dense fibrocartilagenous disc in between which allows minimal movement
What does pregnancy do to the pubic symphysis?
Softens and loosens the pubic symphysis
Hip joint type
Ball and socket
Synovial and multi-axial
What bones articulate in the hip joint?
head of the femur and the acetabulum of the innominate bone
It is one of the most secure, yet very mobile joints
What is the acetabulum?
Incomplete ring on the lateral surface of the innominate bone
See figure
What closes the acetabulum?
transverse acetabular ligament
What is the acetabular fossa?
Deepest part of the acetabulum
Does not articulate with the femur
What is the lunate surface of the acetabulum?
Horseshoe shaped articular
(hyaline) cartilage
Articulates with the head of the femur
Parts of femur (proximal end) and functions
Neck: joins the head to the shaft of the long bone
Greater and lesser trochater: prominences for muscle attachments
Intertrochanteric line: joint and ligaments attach here
See figure
Characteristics of hip joint and capsule
Tight, strong, extensive
Where doe the hip joint capsule extend from? What is it reinforced by?
Extends from just beyond the outer edge of the acetabulum over femur to attach to level area around intertrochanteric line.
Reinforced by 3 strong thick ligaments which all resist excessive abduction: Ilio-femoral, Ischio-femoral, Pubo-femoral
What bones form the knee joint?
Femur, patella, tibia
Fibula is not part of knee joint
See figure
What is the largest and most complex joint in the human body?
Knee joint
Knee joint type?
Synovial
Modified hinge
Stability of knee joint
Lacks bony stability
Stability is dependent on soft tissue structures (muscles, tendons and ligaments)
What bones form the patellofemoral joint (PFJ)?
Articulation between the trochlea of the femur and the posterior surface of the patella.
What is the centerpiece of the extensor mechanism?
PFJ
Knee movements
Modified Hinge Joint: “Screw Home Mechanism”: rotates when it comes into
full extension
Primary: Flexion / Extension (approx. 135 degrees)
Secondary: Medial / Lateral Rotation when flexed
(Approx. 45 degrees when knee flexed to 90 degrees)
Ligamentous support of the knee
Medial collateral ligament (MCL)
Lateral collateral ligament (LCL)
Anterior cruciate ligament (ACL)
Posterior cruciate ligament (PCL)
Meniscus
Shape of MCL
Fan shaped
What does the MCL attach to?
medial femoral epicondyle proximally and medial surface of the tibia distally
Also attached to the medial meniscus
Role of MCL
Resists valgus force
See figure
Shape of lateral collateral ligament (LCL)
Cord like
Easily palpated
What is LCL attached to?
From lateral epicondyle of the femur to fibular head
Role of LCL
Resists varus force
Where are cruciate ligaments of knee found?
Contained in thin, vascularized envelope formed by synovial lining
Blood supply of cruciate ligaments
Poor blood supply
Inadequate ability to heal
Function cruciate ligaments
1° restraint: Tibial translation (TT)
2 ° restraint: Int / Ext rotation and Varus / Valgus angulation
Location/attachments of ACL
APEX
Attaches to the Anterior portion of the intercondylar eminence.
Runs in a Posterior / Superior direction
Runs towards the External aspect of the joint
Note: medial surface of the lateral femoral condyle
Location/attachment of PCL
PAIN
Attaches to the Posterior aspect of the intercondylar eminence
Runs in and Anterior direction toward the front of the knee joint
Runs inward towards the Internal aspect of the
Note: lateral surface of the medial femoral condyle