1. The Knee Joint10-1 Chapter 10 The Knee Joint

2. The Knee Joint10-2 The Knee Joint Knee jointKnee joint –largest joint in body –very complex –primarily a hinge joint

3. The Knee Joint10-3 Bones Enlarged femoral condyles articulate on enlarged tibial condylesEnlarged femoral condyles articulate on enlarged tibial condyles Medial & lateral tibial condyles (medial & lateral tibial plateaus) - receptacles for femoral condylesMedial & lateral tibial condyles (medial & lateral tibial plateaus) - receptacles for femoral condyles Tibia – medialTibia – medial –bears most of weight

4. The Knee Joint10-4 Bones Fibula - lateralFibula - lateral –serves as the attachment for knee joint structures –does not articulate with femur or patella –not part of knee joint

5. The Knee Joint10-5 Bones PatellaPatella –sesamoid (floating) bone –imbedded in quadriceps & patellar tendon –serves similar to a pulley in improving angle of pull, resulting in greater mechanical advantage in knee extension

6. The Knee Joint10-6 Bones Key bony landmarksKey bony landmarks –Superior & inferior patellar poles –Tibial tuberosity –Gerdy’s tubercle –Medial & lateral femoral condyles –Upper anterior medial tibial surface –Head of fibula

7. The Knee Joint10-7 Bones Three vasti muscles of quadriceps originate on proximal femur & insert on patellar superior poleThree vasti muscles of quadriceps originate on proximal femur & insert on patellar superior pole –insertion is ultimately on tibial tuberosity via patella tendon Iliotibial tract of tensor fasciae latae inserts on Gerdy’s tubercleIliotibial tract of tensor fasciae latae inserts on Gerdy’s tubercle Sartorius, gracilis, & semitendinosus insert just below the medial condyle on upper anteromedial tibial surfaceSartorius, gracilis, & semitendinosus insert just below the medial condyle on upper anteromedial tibial surface

8. The Knee Joint10-8 Bones Semimembranosus inserts posteromedially on medial tibial condyleSemimembranosus inserts posteromedially on medial tibial condyle Biceps femoris inserts primarily on fibula headBiceps femoris inserts primarily on fibula head Popliteus originates on lateral aspect of lateral femoral condylePopliteus originates on lateral aspect of lateral femoral condyle Tibial collateral ligament originates on medial aspect of upper medial femoral condyle & inserts on medial tibial surfaceTibial collateral ligament originates on medial aspect of upper medial femoral condyle & inserts on medial tibial surface Fibula collateral originates on lateral femoral condyle very close to popliteus origin & inserts on fibular headFibula collateral originates on lateral femoral condyle very close to popliteus origin & inserts on fibular head

9. The Knee Joint10-9 Joints Knee joint proper (tibiofemoral joint)Knee joint proper (tibiofemoral joint) –classified as a ginglymus joint Sometimes referred to as trochoginglymus joint internal & external rotation occur during flexionSometimes referred to as trochoginglymus joint internal & external rotation occur during flexion Some argue for condyloid classificationSome argue for condyloid classification Patellofemoral jointPatellofemoral joint –arthrodial classification –gliding nature of patella on femoral condyles

10. The Knee Joint10-10 Joints Ligaments provide static stabilityLigaments provide static stability Quadriceps & hamstrings contractions produce dynamic stabilityQuadriceps & hamstrings contractions produce dynamic stability Articular cartilage surfaces on femur & tibiaArticular cartilage surfaces on femur & tibia Menisci form cushions between bonesMenisci form cushions between bones –attached to tibia –deepen tibial fossa –enhance stability

11. The Knee Joint10-11 Joints Medial meniscus forms receptacle for medial femoral condyle, Lateral meniscus receives lateral femoral condyleMedial meniscus forms receptacle for medial femoral condyle, Lateral meniscus receives lateral femoral condyle –Thicker on outside border & taper down very thin to inside border –Can slip about slightly, but held in place by various small ligaments –Medial meniscus - larger & more open C appearance –Lateral meniscus - closed C configuration

12. The Knee Joint10-12 Joints –Either or both menisci may be torn in several different areas from a variety of mechanisms, resulting in varying degrees of problems Tears often occur due significant compression & shear forces during rotation while flexing or extending during quick directional changes in runningTears often occur due significant compression & shear forces during rotation while flexing or extending during quick directional changes in running

13. The Knee Joint10-13 Joints Anterior & posterior cruciate ligamentsAnterior & posterior cruciate ligaments –cross within knee between tibia & femur –vital in respectively maintaining anterior & posterior stability, as well as rotatory stability Anterior cruciate ligament (ACL) injuriesAnterior cruciate ligament (ACL) injuries –one of most common serious injuries to knee –mechanism often involves noncontact rotary forces associated with planting & cutting, hyperextension, or by violent quadriceps contraction which pulls tibia forward on femur

14. The Knee Joint10-14 Joints Posterior cruciate ligament (PCL) injuriesPosterior cruciate ligament (PCL) injuries –not often injured –mechanism of direct contact with an opponent or playing surface Fibular (lateral) collateral ligament (LCL)Fibular (lateral) collateral ligament (LCL) –infrequently injured

15. The Knee Joint10-15 Joints Tibial (medial) collateral ligament (MCL)Tibial (medial) collateral ligament (MCL) –maintains medial stability by resisting valgus forces or preventing knee from being abducted –injuries occur commonly, particularly in contact or collision sports –mechanism of teammate or opponent may fall against lateral aspect of knee or leg causing medial opening of knee joint & stress to medial ligamentous structures

16. The Knee Joint10-16 Joints Synovial cavitySynovial cavity –supplies knee with synovial fluid –lies under patella and between surfaces of tibia & femur –"capsule of the knee” Infrapatellar fat padInfrapatellar fat pad –just posterior to patellar tendon –an insertion point for synovial folds of tissue known as “plica” an anatomical variant that may be irritated or inflamed with injuries or overuse of the kneean anatomical variant that may be irritated or inflamed with injuries or overuse of the knee

17. The Knee Joint10-17 Joints BursaeBursae –more than 10 bursae in & around knee –some are connected to synovial cavity –they absorb shock or prevent friction

18. The Knee Joint10-18 Joints Extends to 180 degrees (0 degrees of flexion)Extends to 180 degrees (0 degrees of flexion) Hyperextension of 10 degrees or > not uncommonHyperextension of 10 degrees or > not uncommon Flexion occurs to about 140 degreesFlexion occurs to about 140 degrees With knee flexed 30 degrees or >With knee flexed 30 degrees or > –internal rotation 30 degrees occurs –external rotation 45 degrees occurs

19. The Knee Joint10-19 Joints Knee “screws home” to fully extend due to the shape of medial femoral condyleKnee “screws home” to fully extend due to the shape of medial femoral condyle –As knee approaches full extension tibia must externally rotate approximately 10 degrees to achieve proper alignment of tibial & femoral condyles –In full extension close congruency of articular surfacesclose congruency of articular surfaces no appreciable rotation of kneeno appreciable rotation of knee –During initial flexion from full extension knee “unlocks” by tibia rotating internally, to a degree, from its externally rotated position to achieve flexionknee “unlocks” by tibia rotating internally, to a degree, from its externally rotated position to achieve flexion

20. The Knee Joint10-20 Movements FlexionFlexion –bending or decreasing angle between femur & leg, characterized by heel moving toward buttocks ExtensionExtension –straightening or increasing angle between femur & lower leg

21. The Knee Joint10-21 Movements External rotationExternal rotation –rotary movement of leg laterally away from midline Internal rotationInternal rotation –rotary movement of lower leg medially toward midline Neither will occur unless flexed 20-30 degrees or >Neither will occur unless flexed 20-30 degrees or >

22. The Knee Joint10-22 Muscles Quadriceps muscle groupQuadriceps muscle group –extends knee –located in anterior compartment of thigh –consists of 4 muscles rectus femorisrectus femoris vastus lateralisvastus lateralis vastus intermediusvastus intermedius vastus medialisvastus medialis

23. The Knee Joint10-23 Muscles Q angleQ angle –Central line of pull for entire quadriceps runs from ASIS to the center of patella –Line of pull of patella tendon runs from center of patella to center of tibial tuberosity –Angle formed by the intersection of these two lines at the patella is the Q angle –Normally, angle will be 15 degrees or less for males & 20 degrees or less in females –Generally, females have higher angles due to a wider pelvis

24. The Knee Joint10-24 Muscles Q angleQ angle –Higher Q angles generally predispose people in varying degrees to a variety of potential knee problems including lateral patellar subluxation or dislocation, patellar compression syndrome, chondromalacia, and ligamentous injuries –For people with above normal Q angles, it is particularly important to maintain high levels of strength & endurance in vastus medialis so as to counteract lateral pull of vastus lateralis

25. The Knee Joint10-25 Muscles Hamstring muscle groupHamstring muscle group –responsible for knee flexion –located in posterior compartment of thigh –consists of 3 muscles semitendinosus - medial, internal rotatorsemitendinosus - medial, internal rotator semimembranosus - medial, internal rotatorsemimembranosus - medial, internal rotator biceps femoris - lateral, external rotatorbiceps femoris - lateral, external rotator Popliteus assist medial hamstrings in knee internal rotationPopliteus assist medial hamstrings in knee internal rotation

26. The Knee Joint10-26 Muscles Two-joint musclesTwo-joint muscles –Most effective when either origin or insertion is stabilized to prevent movement in direction of the contacting muscle –To a degree, muscles are able to exert greater force when lengthened than when shortened –Hamstring muscles & rectus femoris are biarticular (two-joint) muscles

27. The Knee Joint10-27 Muscles Ex. sartorius muscleEx. sartorius muscle –increases its total length & becomes a better flexor at knee when pelvis is rotated posteriorly & stabilized by abdominal muscles exemplified by trying to flex knee & cross the legs in the sitting positionexemplified by trying to flex knee & cross the legs in the sitting position one usually leans backward to flex legs at kneesone usually leans backward to flex legs at knees –Football kicker invariably leans well backward to raise & fix the rectus femoris origin to make it more effective as a knee extensor

28. The Knee Joint10-28 Muscles Gracilis, sartorius, & semitendinosus join together distally to form pes anserinusGracilis, sartorius, & semitendinosus join together distally to form pes anserinus –attaches to anteromedial aspect of proximal tibia below the level of tibial tuberosity –Their attachment & posteromedially line of pull enable them to assist with knee flexion particularly once the knee is flexed & hip is externally rotated Medial & lateral gastrocnemius heads attach posteriorly on medial & lateral femoral condylesMedial & lateral gastrocnemius heads attach posteriorly on medial & lateral femoral condyles –assist with knee flexion

29. The Knee Joint10-29 Muscles Knee joint muscles location Anterior - primarily knee extensionAnterior - primarily knee extension –Rectus femoris –Vastus medialis –Vastus intermedius –Vastus lateralis

30. The Knee Joint10-30 Muscles Knee joint muscles location Posterior - primarily knee flexionPosterior - primarily knee flexion –Biceps femoris –Semimembranosus –Semitendinosus SartoriusSartorius GracilisGracilis PopliteusPopliteus GastrocnemiusGastrocnemius

31. The Knee Joint10-31 Nerves Femoral nerves innervates the knee extensors (quadriceps)Femoral nerves innervates the knee extensors (quadriceps) –rectus femoris –vastus medialis –vastus intermedius –vastus lateralis

32. The Knee Joint10-32 Nerves Sciatic nerveSciatic nerve –tibial division semitendinosus, semimembranosus, biceps femoris (long head)semitendinosus, semimembranosus, biceps femoris (long head) –common peroneal (fibular) division biceps femoris (short head)biceps femoris (short head)

33. The Knee Joint10-33 Quadriceps Muscles Quadriceps muscles - vital in jumpingQuadriceps muscles - vital in jumping –functions as a decelerator when decreasing speed to change directionwhen decreasing speed to change direction when coming down from a jumpwhen coming down from a jump –eccentric contraction during decelerating actions –controls slowing of movements initiated in previous phases of the sports skill

34. The Knee Joint10-34 Quadriceps Muscles Rectus femoris (two-joint), vastus medialis, vastus intermedius, vastus lateralis (largest)Rectus femoris (two-joint), vastus medialis, vastus intermedius, vastus lateralis (largest) All attach to patella then to tibial tuberosity via patellar tendonAll attach to patella then to tibial tuberosity via patellar tendon All superficial & palpable except vastus intermedius (under rectus femoris)All superficial & palpable except vastus intermedius (under rectus femoris) Strength or power may be indicated by vertical jump testStrength or power may be indicated by vertical jump test Generally desired to be 25% to 33% stronger than hamstring groupGenerally desired to be 25% to 33% stronger than hamstring group

35. The Knee Joint10-35 Quadriceps Muscles Strength & endurance is essential for maintenance of patellofemoral stabilityStrength & endurance is essential for maintenance of patellofemoral stability –often a problem –quads are particularly prone to atrophy when injuries occur –may be developed by resisted knee extension activities from a seated position –functional weight bearing activities such as step-ups or squats are particularly useful for strengthening & endurance

36. The Knee Joint10-36 Rectus Femoris Muscle Flexion of hip Extension of knee Anterior pelvic rotation

37. The Knee Joint10-37 Vastus Lateralis Muscle Extension of knee

38. The Knee Joint10-38 Vastus Intermedius Muscle Extension of knee

39. The Knee Joint10-39 Vastus Medialis Muscle Extension of knee

40. The Knee Joint10-40 Hamstring Muscles Hamstring muscle groupHamstring muscle group –Semitendinosus –Biceps femoris –Semimembranosus

41. The Knee Joint10-41 Hamstring Muscles Hamstring muscle strains very commonHamstring muscle strains very common “Running muscles” function in acceleration“Running muscles” function in acceleration Antagonists to quadriceps muscles at kneeAntagonists to quadriceps muscles at knee Named for cordlike attachments at kneeNamed for cordlike attachments at knee All originate on ischial tuberosity of pelvisAll originate on ischial tuberosity of pelvis Semitendinosus inserts on anteromedial tibiaSemitendinosus inserts on anteromedial tibia Semimembranosus inserts on posteromedial tibiaSemimembranosus inserts on posteromedial tibia Biceps femoris inserts on lateral tibial condyle & head of fibulaBiceps femoris inserts on lateral tibial condyle & head of fibula

42. The Knee Joint10-42 Semitendinosus Muscle Flexion of knee Extension of hip Internal rotation of hip Internal rotation of flexed knee Posterior pelvic rotation

43. The Knee Joint10-43 Semimembranosus Muscle Flexion of knee Extension of hip Internal rotation of hip Internal rotation of flexed knee Posterior pelvic rotation

44. The Knee Joint10-44 Biceps Femoris Muscle Flexion of knee Extension of hip External rotation of hip External rotation of flexed knee Posterior pelvic rotation

45. The Knee Joint10-45 Popliteus Muscle Flexion of knee Internal rotation of flexed knee

46. The Knee Joint10-46 Knee Extension AgonistsAgonists –Rectus Femoris –Vastus Lateralis –Vastus Intermedius –Vastus Medialis

47. The Knee Joint10-47 Knee Flexion AgonistsAgonists –Biceps Femoris (Long & Short Head) –Semitendinosus –Semimembranosus

48. The Knee Joint10-48 Knee Internal Rotation AgonistsAgonists –Semitendinosus –Semimembranosus –Popliteus

49. The Knee Joint10-49 Knee External Rotation AgonistsAgonists –Biceps Femoris

50. The Knee Joint10-50 Web Sites University of Arkansas Medical School Gross Anatomy for Medical Students http://anatomy.uams.edu/anatomyhtml/gross.html – –Dissections, anatomy tables, atlas images, links, etc. Loyola University Medical Center: Structure of the Human Body www.meddean.luc.edu/lumen/meded/grossanatomy/index.htm – –An excellent site with many slides, dissections, tutorials, etc. for the study of human anatomy Arthroscopy.com www.arthroscopy.com/sports.htm – –Patient information on various musculoskeletal problems of the lower extremity Wheeless’ Textbook of Orthopaedics www.wheelessonline.com/ – –This site has an extensive index of links to the fractures, joints, muscles, nerves, trauma, medications, medical topics, lab tests, and links to orthopedic journals and other orthopedic and medical news.

51. The Knee Joint10-51 Web Sites Human Anatomy Online www.innerbody.com/image/musc08.html – –Interactive musculoskeletal anatomy American Academy of Orthopaedic Surgeons http://orthoinfo.aaos.org/category.cfm?topcategory=Knee – –Patient education library on the knee The Physician and Sportsmedicine www.physsportsmed.com/issues/1997/05may/bach.htm – –Acute Knee Injuries: When to Refer The Physician and Sportsmedicine www.physsportsmed.com/issues/1999/10_01_99/laprade.htm – –Acute Knee Injuries: On-the-Field and Sideline Evaluation Virtual Hospital www.vh.org – –Numerous slides, patient information, etc.

52. The Knee Joint10-52 Web Sites The Hip and Knee Institute www.hipsandknees.com/knee/index.html – –Arthritis of the Knee Joint Adam Healthcare Center http://adam.about.com/surgery/100088.htm# – –Knee joint replacement Edheads Activities www.edheads.org/activities/knee/ – –Allows you to perform virtual knee surgery Gross Anatomy: The Functional Anatomy of the Knee Joint www.upstate.edu/cdb/grossanat/limbs8.shtml – –Functional Anatomy of the Knee Knee Ligament Anatomy and Injury www.orthoassociates.com/knee_lig.htm – –Anatomy and injuries of the Knee and its ligaments

53. The Knee Joint10-53 Web Sites Smart Play: The Knee www.smartplay.net/ouch/bodybits/b_bitsknee.html – –Anatomy, functions, injuries, etc. of the knee Chiroweb.com www.chiroweb.com/archives/21/24/03.html – –Abnormal Q Angle and Orthotic Support