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;