LOWER EXTREMITY KINES Flashcards
Function of collateral ligaments
prevent frontal plane movement of the knee (abduction and adduction)
Medial Collateral Ligament
restraint against VALGUS stress and thus prevents abduction of the knee
Lateral Collateral Ligament
restraint against VARUS stress and thus prevents adduction of the knee
Anterior Cruciate Ligament (ACL)
APEX: runs anterior to posterior and externally
- fibers are taut in extension; primary restraint against hyperextension of the knee
Function of ACL
Limits ANTERIOR translation of tibia on the femur or POSTERIOR translation of femur on the tibia
- also limits axial rotation of the knee, especially external rotation
Posterior Cruciate Ligament (PCL)
PAIN- runs Posterior to Anterior and Internally
- All fibers taut in flexion
Function of PCL
Limits posterior translation of the tibia on the femur or anterior translation of the femur on the tibia
- prevents the femoral condyles from sliding off the anterior edge of the tibia
Primary extensors of the knee
QUADS
- isometric activation helps to stabilize and protect the knee
- eccentric activation helps to dampen loading and acts as a brake or decelerator of knee flexion during walking, squatting, sitting..ect
- concentric activation accelerates the tibia or femur into extension during walking or standing
Eccentric vs Concentric
Stand to sit=eccentric
STAND TO SIT IS EASIER
sit to stand=concentric
SIT TO STAND REQUIRES MORE CONCENTRATION?
The Patella on the quadriceps
- Patella displaces the quads tendon away from the joint axis, thus increasing the moment arm of the quads
- provides substantial augmentation of extensor torque
Knee flexor-rotator muscles
- with exception of the gastrocnemius, all muscles that cross posterior to the knee joint have the ability to flex and axially rotate the knee
includes HAMSTRINGS, SARTORIUS, GRACIALIS, AND POPLITEUS
Primary flexors of the knee
THE HAMSTRINGS
- medial hamstrings (semitendinosus) internally rotate the knee
- lateral hamstring (biceps femoris) externally rotates the knee
The hamstrings and gait
- active eccentrically to decelerate the advancing tibia at the late swing phase
- active concentrically to accelerate knee flexion in order to shorten the lower limb during early swing phase
Other knee flexor-rotator muscles
sartorius, gracilis (flexors and internal rotators of the knee)
- added effect of providing significant dynamic stability to medial knee
Popliteus
- flexes and internally rotates the knee
- “key to the knee” provides the necessary internal rotation torque to mechanically unlock the knee
To maximally stretch the quads you would
extend hip and flex knee
the quads will
flex the hip joint and extend the knee joint!
All of the following are capable of flexing the hip EXCEPT
Semitendinosus (a hamstring muscle) WE KNOW HAMSTRING EXTEND THE HIP JOINT
SARTORIUS, RECTUS FEMORIS, AND ILLIACUS CAN FLEX THE HIP
Dropping of the pelvis on the right side during single limb support over the left leg most likely indicates weakness of
THE LEFT GLUTEUS MEDIUS
The sartorius muscle can perform all of the following except
KNEE EXTENSION
- sartorius can flex hip, flex knee and internally rotate knee
Which of the following muscles can produce movement at both the hip and knee
RECTUS FEMORIS
To maximally stretch HAMSTRING you would
flex hip, extend knee, anterior pelvic tilt
to maximally stretch hip FLEXORS the pelvis should be
Posteriorly tilted
Psoas major
hip flexion
semitendinous
knee internal rotation
biceps femoris
knee external rotation
obturator externus
hip external rotation
pectineus
hip adduction
the knee joints
tibial-femoral joint (medial and lateral articulations)
patello-femoral joint
knee moves in what plane
sagittal and horizontal
Function of menisci
reduce compressive stress SHOCK ABSORPTION and reduce stress on cartilage
- supports 1/2 load across the knee
How is knee joint stabilized?
articular surfaces, quads, retinacular fibers
locking of the knee
Locking of the knee in terminal extension requires 10 degrees of external rotation
Before flexion can occur
the knee must be unlocked by internally rotating the knee
- driven by the popliteus muscle
internal/external rotation of the knee can only occur
AFTER the knee has been unlocked (out of terminal extension)
Ligaments of the hip
- illiofemoral
-ischiofemoral - pubofemoral
limits extremes of all movements of the hip, all three are partially taut in full extension of the hip