Kinesiology chapter 19: Knee Joint
menisci
2; medial and lateral; cartilaginous structures that increase stability; attached to tibia, deepen tibial fossa, enhance stability, acts as shock absorbers; form cushions between bones
lateral collateral ligament (LCL)
attaches from lateral epicondyle of femur to fibular head; prevents knee hyperextension; provides lateral stability when a varus stress is applied; infrequently injured
medial collateral ligament (MCL)
attaches from medial epicondyle of femur to medial tibia; provides medial stability when a valgus stress is applied; prevents excessive motion if there is a blow to the lateral aspect of knee; injuries occur commonly, particularly in contact or collision sports; mechanism of teammate or opponent may fall against lateral aspect of knee joint and stress to medial ligamentous structures
posterior cruciate ligament (PCL)
attaches from posterior lateral tibia to anterior medial condyle of femur; prevents hyperflexion of knee; prevents posterior displacement of tibia relative to femur; prevents anterior displacement of femur relative to tibia; not often injured
anterior cruciate ligament (ACL)
attaches from the anterior medial tibial to posterior lateral condyle of femur; prevents hyperextension of knee; prevents anterior displacement of tibia relative to femur; prevents posterior displacement of femur relative to tibia
tibia
bears most of the weight
popliteal space
behind knee; contains important nerves (tibial and common peroneal) and blood vessels (popliteal artery and vein)
flexion
bending or decreasing angle between femur and leg; characterized by heel moving towards buttocks
knee external rotator
biceps femoris
knee flexors
biceps femoris, semimembranosus, semitendinosus (sartorius, gracilis, popliteus, gastrocnemius); located posteriorly
Q angle
central line of pull for entire quadriceps runs from ASIS to center of patella; line of pull of patella tendon runs from center of patella to center of tibial tuberosity; angle formed by intersection of these 2 lines at patella; females have higher angles
action of vastus medius, lateralis, intermedius
extension of knee
action of rectus femoris
flexion of hip, extension of knee anterior pelvic rotation
action of biceps femoris
flexion of knee; extension of hip; external rotation of hip; external rotation of flexed knee; posterior pelvic rotation
action of semitendinosus and semimembranosus
flexion of knee; extension of hip; internal rotation of hip; internal rotation of flexed knee; posterior pelvic rotation
action of popliteus
flexion of knee; internal rotation of flexed knee
frontal axis
in which axis does the knee move
sagittal plane
in which plane does the knee move
knee joint
largest joint in body; uniaxial joint = 2 motions: flexion/extension; very complex = has a lot of ligaments; primarily a hinge joint; most commonly injured joint in body
bursae
more than 13 in and around knee; some are connected to synovial cavity; purpose is to reduce friction
tibial nerve
nerve that innervates muscles that cause knee flexion; gastrocnemius and popliteus
femoral nerve
nerve that innverates muscles that cause knee extension; quadriceps; branches: saphenous and cutaneous
ACL injury
one of most common serious injuries to knee; mechanism often involves noncontact rotary forces associated with planting and cutting, hyperextension, or by violent quadriceps contraction which pulls tibia forward on femur
pes anserinus
provides additional stability medially knee; sartorious, gracilis, semitendinosus; all cross knee joint posteriorly and medially; inserts at anteromedial tibia
muscles of quadriceps
rectus femoris, vastus medialis, vastus intermedius, vastus lateralis; all attach to patella the to tibial tuberostiy via patellar tendon, all superficial and palpable except vastus intermedius, strength or power may be indicated by vertical jump test, stronger than hamstrings
knee extensors
rectus femoris, vastus medialis, vastus intermedius, vastus lateralis; located anteriorly
external rotation
rotary movement of lower leg laterally away from midline
internal rotation
rotary movement of lower leg medially toward midline
knee internal rotators
semitendinosus; semimembranosus; popliteus
fibula
serves as the attachment for knee joint structures; does not articulate with femur or patella; not part of knee joint
patella
sesamoid bone; floating; imbedded in quadriceps & patellar tendon; serves similar to a pulley in improving angle of pull, resulting in greater mechanical advantage in knee extension
extension
straightening or increasing angle between femur and lower leg
hamstring muscles
strains very common; running muscles function in acceleration; antagonists to quadriceps at knee; named for cordlike attachments at knee; all originate on ischial tuberosity of pelvis; semitendinosus (inserts on anteromedial tibia), biceps femoris (inserts on lateral tibial condyle & head of fibula), semimembranosus (inserts on posteromedial tibia)
valgus stress
stress that comes laterally; patient walks with knees touching; feet are at a greater angle than knees; affects MCL
varus stress
stress that comes medially; patient walks bow-legged; knees are at a greater angle than feet; affects LCL
quadriceps muscles
vital in jumping; functions as a decelerator (when decreasing speed to change direction; when coming down from a jump); eccentric contraction during decelerating actions; controls slowing of movements initiated in previous phases of sports skill;