Knee Anatomy Flashcards
List the anatomical structures of the knee
- Femur
- Tibia
- Fibula
- Patella
- Knee Meniscus
- Ligaments
- Capsule
- Hoffa’s Fat Pad
- Plicae, Bursae, Synovial lining
- Musculature
describe the femoral shaft
- inclined ~10º from vertical
- made up of dense compact bone with a medullary cavity
- trabecular bones at proximal and distal ends
What is the Q-angle? What is a normal value for it?
angle formed by
- line from midpoint of patella to tibial tubercle
- line from ASIS to mid point of patella
- normal = 13.5º (+/- 4.5)
describe the distal femur osseous structures
- Patellar surface
- anterior expansion of both condyles
- groove for patella
- Medial condyle
- slightly curved, medial convexity
- Lateral condyle
- Intercondylar fossa
list and describe osseous structures found at the proximal tibia
- Condyles
- Tibial tuberosity
- anterior ridge where anterior surface of condyles meet
- Fibular facet
- posterio-inferior lateral condyle
- Gerdy’s tubercle
- anterio-lateral lateral condyle
- insertion of ITB
- Intercondylar area
- attachments for horns of menisci
- intercondylar eminence is the central, most narrow raised portion and ACL attachment
T/F: the fibular is a good weight bearing bone?
FALSE
patellar orientation
Base = superior
apex = inferior
typically, apex should be slightly proximal to tibiofemoral joint line in extended position
describe the articular surface of the patellar
- vertical ridge fits into intercondylar groove of femur’s patellar surface
- divides patellar articular area into M/L facets
- facets further divided into equal 3rds
- 7th odd facet located on the medial border that contacts the femoral condyle in full flexion
- divides patellar articular area into M/L facets
describe the infrapatellar (Hoffa’s) Fat Pad
- Intra-capsular
- Extra-synovial
- Contacts infrapatellar plica
- Highly vascularized
- Highly innervated
what is the function of Hoffa’s Fat Pad?
- Biomechanical role
- space decreases f/b lateral protrusion of this in increasing flexion
- Reservoir for reparative cells
describe the knee joint capsule
- fibrous sleeve spanning from distal femur to proximal tibia
- cylindrical shape
- blends with PCL posteriorly
- Patella recieved in window of anterior surface
describe the femoral insertion of the knee capsule
- anteriorly forms supratrochlear fossa
- posteriorly condylar plates, distal to gastroc insertions
- Cruciate ligaments blend with capsule at insertion
List the ligaments of the knee
- MCL
- LCL
- ACL
- PCL
describe the structure of the MCL
- origin/insertion
- medial condyle to upper tibia
- posterior horn of medial meniscus and capsule
- general orientation
- obliquely, anteriorly, inferiorly
- taut during extension, slackened during flexion
- least taut at 30º of flexion
what is the function of the MCL
- checks/limits genu valgus
- prevents lateral rotation (with knee in extended position)
describe the structure of the LCL
- Origin/Insertion
- lateral epicondyle to head of fibula (blends with biceps femoris insertion
- Orientation
- inferiorly and posteriorly
- Distinct from capsule
- separated from lateral meniscus by popliteus tendon
what is the function of the LCL?
- checks/limits varus force
- least taut at 30º of flexion
describe the structure of the ACL
- attachment sites
- posterior aspect of the lateral femoral condyle’s medial surface
- anterior and lateral to the medial tibial spine
- courses anteriorly, medially, and distally
- made up of an AMB and PMB
- intermediate bundle described by some authors
what is the vascularization and innervation to the ACL?
- Vascularization = proximal > distal portion
- Innervation:
- branches of the posterior articular branches of the tibial nerve (proprioceptive)
what is the function of the ACL?
- Sagittal plane → stability to the knee joint, resisting anterior tibial translation
- Frontal plane → varus and valgus (minimally)
- Horizontal plane → tibial rotation
describe the structure of the PCL
- thicker and stronger than ACL
- attachment sites
- lateral surface of medial femoral condyle to anterior roof of the intercondylar notch
- Fan-like structure, fiber orientation variable
- anterolateral and posteriomedial bundles
- named to femoral attachments
what is the function of the PCL?
pulls condyles posteriorly during extension
describe the medial meniscus
- broader posteriorly
- nearly semicircle
- anterior horn attached to anterior tibial intercondylar (anterior to ACL)
- posterior horn attached to posterior tibial intercondylar area
- peripheral border attached to capsule and deep MCL
- coronary ligament is the tibial attachment of the meniscus
which menisci moves more?
lateral > medial
describe the lateral meniscus
- 4/5ths of a circle
- anterior horn attached anterior to the intercondylar eminence
- meniscofemoral ligaments often only attachment of the posterior horn
- tendon of popliteus is attached to the lateral meniscus
- no peripheral bony attachment in area of popliteus
how well vascularized are the knee menisci?
- vascularized by middle genicular artery and branches
- peripheral 10-30% vascularized
- rich innervation at horns
- inner portions
- avascular
- non-innervated
what is the function/purpose of the menisci?
- Increase congruency of joint
- spread loading
- physical stability
- provide proprioceptive input
- lubrication
- attenuate loading during extremes of flexion and extension
what/where is the patellar retinaculum?
- expansions form VM and VL that is separated by a plane of vascularized loose CT
- attached to the patellar margins and patellar tendon
- laterally reinforced by ITB
what muscles extend the knee?
- quads
- TFL
what muscles flex the knee?
- Biceps femoris
- Semitendinosus
- Semimembranous
- Gracilis
- Sartorius
- Popliteus
- Gastroc and Plantris (with stationary foot)
list the medial rotators of the knee
- Semimembranosus
- Semitendinosus
- Popliteus
- Gracilis
- Sartorius
list the lateral rotators of the knee
biceps femoris
describe normal osteokinematics and ranges for motion at the knee
- Flexion
- Active → 130
- Passive → 160
- Extension
- 5-10
- IR and ER
- 60-70 (total)
what is the resting pack and close-pack position for the knee?
- resting position → ~30º flexion
- close-pack position → full extension
describe the arthrokinematics of the patella during knee motion
- extended knee
- inferior patella contacts trochlea
- posterior surface points directly posteriorly
- 30º knee flexion
- mid-patella contacts trochlea
- Full flexion
- superior and superiolateral patella contacts trochlea
- posterior surface faces cranially
describe the screw home mechanism
- ER of tibia in terminal knee extension
- bony congruency
- tauted supportive soft tissue structures
