What is the largest joint in the body, takes a lot of stress, and is frequently injured?
What is the knee joint classified as?
Synovial Hinge Joint
What are the motions possible at the knee?
Flexion and extension, and some rotation that is an accessory motion
What types of arthrokinetmatic motions are used in the knee?
All three: roll, glide, and spin
Which way does the tibia rotate on the femur during non weight bearing extension and what does this rotation result in?
The tibia rotates laterally on the femur and these last few degrees of motion lock the knee in extension; it is called the screw home mechanism of the knee
With the knee fully extended, what can an individual do?
stand for long periods of time without using any muscles
For knee flexion to occur, what must the knee do?
the knee must be 'unlocked' by laterally rotating the femur on the tibia
What keeps the knee from being a true hinge joint?
the small amount of rotation of the femur on the tibia, or vice versa
What type of motion is the the 'screw home mechanism"?
a companion motion used to lock knee in place
For the knee to achieve full extension, what will the tibia do?
the tibia will have to rotate a little bit laterally in open chain to lock
To unlock the knee, the femur will have to rotate?
a little bit laterally
What is moment arm?
the perpendicular distance between the muscles line of action and the center of the joint
Articulation between the femur and the patella is referred to as?
What are the main functions of the patella?
increasing mechanical advantage of the quadriceps muscle and protecting the knee joint
What is the Q Angle?
aka patellofemoral angle, is the angle between the quadriceps muscle (mainly rectus femoris) and the patellar tendon
How is the Q Angle determined?
by drawing a line from the ASIS to the midpoint of the patella, and from the tibial tuberosity to the midpoint of the patella
In knee extension, what is the normal Q angle?
13 - 19 degrees
Is the fibula part of the knee joint?
No, because it does not articulate with the femur
What are the main ligaments that hold the knee together?
the cruciate and the collateral ligaments
What are the cruciates named for?
their attachment on the tibia
The cruciates provide stability on what plane?
What is the purpose of the anterior cruciate ligament?
prevents anterior movement of the tibia
What is the purpose of the posterior cruciate ligament?
prevents posterior movement of the tibia
What do the collateral ligaments do?
supply stability in the frontal plane, tighten during extension, slacken during flexion
What is the lateral collateral ligament?
round, cordlike ligament that attaches to the lateral condyle of the femur and and inserts at the head of the fibula
What does the lateral collateral ligament do?
protects the joint from stresses to the medial side of the knee; quite strong and not commonly injured
What does the medial collateral ligament do?
provides medial stability and prevents excessive motion if there is a blow to the lateral side of the knee
What is the purpose of bursa?
to reduce friction between tendon and bone
Where is the prepatellar bursa located?
between the patella and the skin
Where is the superficial infrapatellar bursa located?
between tibial tuberosity and skin
Where is the deep infrapatellar bursa located?
between proximal tibia and patellar ligament
Where is the pens anserine bursa located?
deep to sartorius, gracilis, and semitendinosus tendons
The Quadriceps muscles are comprised of what 4 muscles that cross the anterior surface of the knee?
Rectus femoris, Vastis lateralis, Vastus, intermedialis, and Vastus medialis
Which one of the quad muscles crosses the hip?
What are the 1 joint muscles of the knee?
Anterior: Vastus lateralis, Vastus medialis, Vastus intermedialis
Posterior: Biceps femoris (short), Popliteus
What are the 2 joint muscles of the knee?
Anterior: Rectus femoris
Posterior: Biceps femoris (long), Semimembranosus, Semitendinosis, Sartorius, Gracilis, Gastrocnemius
Lateral: Tensor fascia latae
The rectus femoris muscle is a prime mover in?
hip flexion and knee extension
Where does the rectus femoris originate?
Where do all the quad muscles (rectus femoris, vastus lateralis, vastus intermedius, vastus medialis) insert?
Tibial tuberosity via patellar tendon
What action do all the quad muscles have in common?
Knee extension; rectus femoris also does hip flexion
What nerve and spinal cord level do all the quad muscles have?
Femoral nerve, L2, L3, L4
What is the origin for the vastus medius and vastus lateralis?
What is the origin of the vastus intermedialis?
What 3 muscles are known as the Hamstring Muscles?
Semimembranosus, Semitendinosus, and Biceps femoris
What are the main actions of the hamstring muscles?
Extend hip and flex knee
What is the only part of the hamstring muscle group that has a function only at the knee?
short head of the biceps femoris does not extend hip
The Semimembranosus and the Semitendinosis both orginate where?
Where does the biceps femoris originate?
Long head: Ishial tuberosity
Short head: lateral lip of linea aspera
What is the nerve and spinal cord segment for Semimembranosus and Semitendinosus?
Sciatic Nerve: L5, S1, S2
What is the nerve and spinal cord level for the Biceps femoris?
Long Head: Sciatic Nerve: S1, S2, S3
Short Head: Common Peroneal nerve: L5, S1, S2
What is the popliteus muscle credited for?
'unlocking' the knee, it initiates knee flexion
Whats is the origin and instertion of the popliteus muscle?
Origin: Lateral condyle of femur
Insertion: posterior medial condyle of tibia
What is the common area for a 'bakers cyst' or synovial hernia?
What muscles are the knee extensors?
Quadriceps: Rectus Femoris, Vastus Medius, Vastus lateralis, Vastus intermedius
What muscles make up the pens anserine muscle group?
Superior to inferior: Sartorius, Gracilis, Semitendinosis
Why is the gastrocnemius muscle unique?
in closed kinetic chain the thigh become moveable so reversal of muscle action can occur; femur can be pulled posteriorly into knee extension which makes it possible for a person to stand upright without using quad muscles
What is the origin and insteriton of the Gastrocnemius?
Origin: Medial and lateral condyles of femur
Insertion: Posterior calcaneus
What is the action of the gastrocnemius?
knee flexion, ankle plantar flexion
What is the nerve and spinal cord level of the gastrocnemius?
Tibial nerve: S1, S2
What muscles have knee extension?
Quadriceps group: Rectus femoris, Vastus medialis, vastus intermedialis, vastis lateralis
What muscles have knee flexion?
Hamstring Group: semimembranosus, semitendinosus, biceps femoris
What muscles are innervated by the femoral nerve and spinal segment L2, L3, L4?
What muscles are intervated by Sciatic nerve and spinal segment L5, S1, S2?
*exception is short head of biceps femoris: Common Peroneal Nerve
What muscles are innervated by the Tibail Nerve?
Popliteus: L4, L5, S1
Gastrocnemius: S1, S2
What is genu valgum?
aka "knock knees" ankles are positione dmore laterally than normal; lateral potion of meniscus has collapsed; seen in conjuction with coxa varus
What is genu varum?
aka "bowlegged" ankles are positioned more medially that normal; medial portion of meniscus has collapsed; seen in conjunction with coxa valgus
What is "Terrible Triad" or "Unhappy Triad"?
knee injusry casued by a single blow and involves tears to the anterior crucistae ligament, the medial collateral ligament, and the medial meniscus