Gross Anatomy-Knee

Question 1

Describe the Knee Joint

Answer 1

• Largest, most superficial joint
• Synovial joint
• Function commonly impaired with hyperextension
• Stability depends on:
o Strength and actions of surrounding mm. and tt.
 Most important
 Most important muscle is quadriceps femoris
• Particularly vastus medialis and lateralis mm.
o Ligaments that connect femur and tibia

• Fibula is not involved in this joint
• Permits flexion/extension, slight medial and lateral rotation (with knee flexed)

Question 2

Describe some features of the Knee Joint.

Answer 2

Features
• Hinge type joint
• Consists of 3 articulations:
o 2 femorotibial (lateral and medial)
 Between lateral and medial femoral and tibial condyles
o 1 femoropatellar
 Between patella and femur
• Joint capsule has opening:
o Posterior to lateral tibial condyle
o Allows t. of popliteus to exit joint capsule
• Anteriorly, quadriceps t., patella and patellar ll. replace fibrous joint capsule
• Knee joint cavity extends superior to patella as suprapatellar bursa
o Synovial membrane of capsule is continuous with synovial lining of bursa
o May extend halfway up anterior femur
o Muscle slips from vastus intermedius form articularis genu m.
 Attach to synovial membrane
 Retract bursa during extension of knee

Question 3

How many Bursae are around the knee joint? Name and describe them.

Answer 3

o At least 12
o Subcutaneous prepatellar and infrapatellar –
 Located at convex surface of joint
 Allow skin move freely during movements of knee
o Four bursae communicate with knee joint synovial cavity:
 Suprapatellar
• Infection in it may spread to knee cavity
 Popliteus
 Anserine
 Gastrocnemius

Question 4

Describe the** Extrascapular Ligaments** of the Knee Joint.

Answer 4

o 5 ligaments
o Patellar l. –
 From apex and adjoining margins of patella to tibial tuberosity
 Anterior l. of knee joint
 Laterally it receives medial and lateral patellar retinacula
• Help form joint capsule
• Help keep patella in alignment
o Fibular collateral l. (FCL) –
 Lateral collateral l. of knee
 Taut with extension
 Strong and cord-like
 From lateral epicondyle of femur to lateral surface of fibular head
 t. of popliteus passes deep to FCL
• Separates FCL from lateral meniscus
 Splits t. of biceps femoris into two parts
o Tibial collateral l. (TCL) –
 Medial collateral l. of knee
 Taut with extension
 Strong and flat
• Weaker than FCL
• More often damaged
 From medial epicondyle of femur to medial surface of tibia
 Deep fibers of TCL are firmly attached to medial meniscus o Oblique popliteal l. –

 Recurrent expansion of t. of semimembranosus
 From medial tibial condyle passing superolaterally to lateral femoral condyle
• Spans intracondylar fossa and blends with joint capsule
 Reinforces joint capsule posteriorly
o Arcuate popliteal l. –
 From posterior aspect of fibular head passing superomedially over t. of popliteus
• Spreads over posterior surface of knee joint
 Strengthens joint capsule posterolaterally

Question 5

Describe the Intracapsular (inta-articular) part knee joint

Answer 5

o Cruciate ll. –
 Cross within joint capsule
• Outside synovial cavity
 Located at center of joint
 Cross each other obliquely
• Like the letter X
 During medial rotation of tibia on femur:
• Wind around each other
• Limits MR to about 10 degrees
 LR is possible to nearly 60 degrees
• Especially when knee is flexed 90 degrees
• Movement ultimately limited by TCL
 In every position, one cruciate l. or parts of one or both ll. is tense
 Anterior cruciate l. (ACL) –
• Weaker
• Poor blood supply
• From anterior intercondylar area
• Extends superiorly, posteriorly and laterally
• Attaches to posterior part of medial side of lateral femoral condyle
• Prevents posterior displacement of femur on tibia
• Prevents hyperextension of knee joint
 Posterior cruciate l. (PCL) –
• Stronger
• From posterior intercondylar area
• Extends superiorly, anteriorly and medially
• Attaches to anterior part of lateral side of medial femoral condyle
• Prevents anterior displacement of femur on tibia
• Prevents posterior displacement of tibia on femur
• Helps prevent hyperflexion of knee joint
• Main stabilizing factor of femur when weight-bearing on the flexed knee (e.g. walking down hill)

o Menisci –
 Crescentic plates of fibrocartilage
 Deepen tibial plateau
 Act as shock absorbers
 Thicker at external margins
 Unattached at interior of joint
 Firmly attached at ends to intercondylar area of tibia
 Coronary ll. – portions of joint capsule
• Extend between margins of menisci and periphery of tibial condyles
 Transverse l. of knee –
• Joins anterior edges of menisci
• Crosses anterior intercondylar area
• Tethers menisci to each other
 Medial meniscus –
• C shaped
• Adheres to deep surface of TCL
• Less mobile on tibial plateau
• More prone to injury
 Lateral meniscus –
• Nearly circular
• Smaller and more freely moveable
• t. of popliteus passes between it and FCL
**• Posterior meniscofemoral l. **
o Joins lateral meniscus to PCL and medial femoral condyle

Question 6

Describe Knee Joint Injuries

Answer 6

• Most common injuries are ligament sprains
• Occur when foot is fixed on the ground
o Force applied to knee when foot is fixed tears ligaments
• Blow to lateral side of extended knee or excessive lateral twisting of flexed knee causes the following:
o Rupture of TCL
o Concomitant tearing of medial meniscus – due to attachment of TCL
o Tearing of ACL may also occur
o Known as “unhappy triad”
• Hyperextension and force directed anteriorly when knee is semi-flexed cause ACL ruptures
o ACL may tear away from tibia or femur, but commonly occur midpoint
o Also common during skiing accidents
o Causes free tibia to slide anteriorly under fixed femur
 Anterior drawer sign
 Tested using Lachman test
• PCL ruptures usually occur in conjunction with FCL or TCL tears
o Occur when knees strike dashboard in car accident
o Allow free tibia to slide posteriorly under fixed femur
 Posterior drawer sign

Question 7

Describe Meniscal Tears

Answer 7

• Most occur in conjunction with TCL or ACL tears
• Usually involved medial meniscus
• Lateral meniscus less likely to be torn due to mobility
• Pain with lateral rotation of tibia on femur indicates lateral meniscus tear
• Pain with medial rotation of tibia on femur indicates medial meniscus tear
• Menisci may be removed
o No loss of mobility
o May be less stable
o Tibial plateau often undergoes inflammatory reactions

Question 8

Describe Exaggerated Knee Angles

Answer 8

• Femur is placed diagonally in thigh, whereas tibia is almost vertical in leg
o Creates angle at knee between long axes of bones
 Known as “Q-angle”
• Angle is typically greater in adult females due to wider pelves
• Assessed by drawing line from ASIS to middle of patella
• A second vertical line passes through middle of patella to tibial tuberosity
o Normal angle of femur in thigh places middle of knee directly inferior to head of femur when standing
 Centers weight-bearing line in intercondylar region of knee
• Genu varum (bowleg)
o Medial angulation of leg in relation to thigh
o Femur is abnormally vertical and Q-angle is small
 Line of weight-bearing falls medial to center of knee
 Results in arthrosis (destruction of knee cartilage)
 Stresses FCL
• Genu valgum (knock-knee)
o Lateral angulation of leg in relation to thigh
o Larger Q-angle
 Line of weight-bearing falls lateral to center of knee
 Results in arthrosis
 Stresses TCL
 Also causes abnormal articulation with patella
• Pulls it further laterally
• Eventually these conditions lead to osteoarthritis (degenerative joint changes)