anatomy of Knee

MOB TCD

Knee

Professor Emeritus Moira O’Brien

FRCPI, FFSEM, FFSEM (UK), FTCD

Trinity College

Dublin

Knee Joint

• Synovial condylar joint• Close pack• Full extension• Least pack• 15 degree flexion

MOB TCD

Anatomy of Knee Joint MOB TCD

Bones

• The articular surfaces are the medial and lateral femoral condyles (the intercondylar notch in between)

• The medial condyle has a longer articular surface

• The superior aspect of the medial and lateral tibial condyles

• The posterior aspect of the patella

MOB TCD

Intercondylar Notch

• Average is 17 mm• Narrow notch more likely to tear ACL

MOB TCD

Bones MOB TCD

Patella

• Sesamoid bone • Thickest articular cartilage in body• Smaller medial facet• Q-angle• Controlled by Vastus Medialis

Obliquus (VMO) and Vastus Lateralis Obliquus (VLO)

MOB TCD

• The patella is controlled by the oblique portions of the vastus medialis and vastus lateralis.

• The vastus medialis wastes within 24 hours after an effusion of the knee

• If the oblique fibers of the vastus medialis are wasted, the patella tends to sublux laterally on extension of the knee. This results in retropatellar pain

Patella MOB TCD

Patella MOB TCD

Weak Vastus Medialis Obliquus

• Lower most fibres of vastus medialis• Partly arise adductor magnus• Straightens the pull on the quads

tendon and patella• Controls patella tracking during

flexion extension of the knee • Fibres atrophy quickly after knee

injury• 10-15 ml of effusion inhibit VMO • VMO rehabilitation strength and

timing of contraction

MOB TCD

Deficiency of Lateral Condyle MOB TCD

Capsular Ligaments

• Quadriceps • Retinacular fibres• Patellar tendon• Coronary ligaments• Medial and lateral ligaments• Posterior oblique ligament

MOB TCD

Capsule Attachments

• Quadriceps tendon• The patella • The patellar ligament • Retinacular fibres all form the

anterior part of the capsule• The patellar ligament is the insertion

of the quadriceps tendon

MOB TCD

Patellar Ligament

• Antero-inferiorly is attached to the tuberosity of the tibia

• On either side the retinacular fibres pass upwards from the tuberosity in a V-shaped manner to be attached just below the articular margin

• The deep infrapatellar bursa and infrapatellar pad of fat lie posterior to it, separating it from the tibia

MOB TCD

Capsule Attachments

• Laterally, the attachment is just beyond the articular margin

• Laterally, it is attached above the groove for the popliteus, below the lateral epicondyle

• There is a gap in the capsule to allow the popliteus to emerge

MOB TCD

• Posterior• Superiorly, it is attached just beyond

the articular margin and to the lower border of the popliteal surface of the femur, above the intercondylar notch

Capsule Attachments MOB TCD

• Postero-inferiorly, the capsule is attached to the medial condyle of the tibia

• By a line running above the groove for the semimembranosus tendon

• Below the attachment of the posterior cruciate ligament


• Medially, the capsule is attached to the femur just beyond the articular margin of the condyle

• Below the medial epicondyle


Collateral Ligaments

Netter

MOB TCD

Medial Structures

• Medial ligament• Pes anserinus consists of:

– Sartorius – Gracilis – Semitendinosus

• Tibial inter-tendinous bursa between them

MOB TCD

Medial Collateral Ligament (MCL) or Tibial Collateral Ligament

• Is attached superiorly to the medial epicondyle of the femur

• It blends with the capsule

• Attached to the upper third of the tibia, as far down as the tibial tuberosity

• It has a superficial and deep portion

• The deep portion, which is short, fuses with the capsule

• Attached to the medial meniscus

• A bursa usually separates the two parts

MOB TCD

• The tendons of sartorius, gracilis and semitendinosus cross its tibial attachment where another bursa is situated

• The anterior part tightens during the first 70–105°of flexion

Medial Collateral Ligament (MCL) or Tibial Collateral Ligament

MOB TCD

• Medial ligament, tightens in extension

• And at the extremes of medial and lateral rotation

• A valgus stress will put a strain on the ligament

• If gapping occurs when the knee is extended, this is due to a tear of posterior medial part of capsule

• If gapping only occurs at 15º flexion, this is due to tear of medial ligament

Medial Collateral Ligament (MCL) MOB TCD

Netter

Medial Ligament MOB TCD

Posterior Medial Structures

• Semimembranosus into the groove on posterior aspect of medial tibial condyle and its extensions

• Upwards and lateral is oblique popliteal ligament

• Downwards and lateral forms fascia covering popliteus

• Downwards and medially fuses with medial ligament

MOB TCD

• Oblique popliteal ligament passes upwards and laterally

• Fuses with the fabella if present• Capsule above lateral femoral condyle• Pierced by middle genicular vessels

and nerve• Posterior division of obturator nerve• Popliteal artery lies on it

Oblique Popliteal Ligament MOB TCD

• Strengthens the posterior portion of the capsule and prevents extreme lateral rotation

• It is an expansion from the semimembranosus tendon close to its insertion to the tibia

• Branch from the posterior division of the obturator nerve, pierces the ligament, supplies cruciates and articular twig to knee (referred pain from pelvic peritoneum to knee)

Oblique Popliteal Ligament MOB TCD

Lateral Structures

Netter

MOB TCD

• Lateral ligament• Iliotibial tract• Arcuate complex

• Fabellofibular ligament• Deep portion of capsule• Meniscotibial ligaments

Lateral Knee MOB TCD

Poster Lateral Corner

• Posterior horn of lateral meniscus

• Arcuate complex • Popliteus• Lateral head of

gastrocnemius

MOB TCD

• Deep in interval between iliotibial band and biceps

• Lateral epicondyle of femur• Midpoint superior surface of

fibula and the styloid process of the fibula

• It is a cord-like structure that is separated from the capsule by the tendon of the popliteus

• Surrounded by bicepsFabbriciani & Oransky, 1992

Lateral Ligament MOB TCD

Lateral Collateral Ligament (LCL)

• Deep to lateral collateral ligament • Popliteus • Inferolateral genicular vessels and

nerve

MOB TCD

Lateral Collateral Ligament (LCL) or Fibular Collateral Ligament

• Taut in extension• 20°flexion, lateral ligament complex

more lax than medial• Primary lateral restraint to varus

loading• Arcuate ligament is the edge of

capsule that arches above the popliteus

MOB TCD

Arcuate Ligament

• Passes from the tip of the styloid process

• Just posterior to the lateral ligament• Blends origin of the lateral head of

gastrocnemius and oblique popliteal ligament

• Edge of capsule arches over popliteus and may give partial origin to popliteus

MOB TCD

Fabella

• Fabella lies at point on the poster lateral side of knee

• Where multidirectional collagenous tensile stress meet

• 8% - 10% osseous• 90% - 92% cartilagenousFabbricani & Oransky, 1992

MOB TCD

Coronary Ligament

• Connects the periphery of the menisci to the tibia

• They are the portion of the capsule that is stressed in rotary movements of the knee

MOB TCD

Popliteus

• Origin inferior, popliteal surface of tibia, above the soleal line, fascia of semimembranosus

• Deep to arcuate popliteal ligament• Enters capsule• Crosses lateral surface of lateral

meniscus• Attached by popliteal-meniscal fibres

which bound hiatus

MOB TCD

• Enters hiatus• Crosses femoral condyle • Deep to lateral collateral

ligament• Inserts into anterior part of

groove• Superior popliteal recess

communicates joint

Popliteus MOB TCD

• Femoral condyles rotate medially around taut ACL during the locking mechanism of the knee

• Popliteus laterally rotates the femur to unlock the knee so flexion can occur

Popliteus MOB TCD

Iliotibial Tract

• The iliotibial tract is a thickening of the deep fascia of the thigh, fascia lata

• The tract is attached to Gerdy’s tubercle on the anterolateral aspect of the lateral tibial condyle

• The superficial three quarters of the gluteus maximus end in a thick tendinous lamina which is inserted into the iliotibial tract

• The tensor fascia lata is also inserted into the tract

• Gives origin to the oblique fibres of the vastus lateralis that help to stabilise the patella

MOB TCD

• In full knee extension the tract lies anteriorly to the line of flexion of the knee,

• As it is free of bony attachments between the lateral femoral epicondyle and Gerdy’s tubercle

• It is free to move posteriorly to this axis on flexion of the knee

Standish & Wood, 1996.

• As the tract crosses the lateral epicondyle of the femur a bursitis may develop as the result of a ‘long-leg syndrome’

Iliotibial Tract MOB TCD

• The iliotibial band acts as an extensor of the knee when the knee is flexed from 0°to 30°and as a flexor when the knee is flexed more than 40°, due to the change in the transverse axis which occurs at 30–40°flexion.

• The pelvic tilt is a mechanism for tightening the iliotibial band. The pull of the band stabilises the knee in extension, as well as helping to resist extension and adduction of the hip of the weight-bearing leg

Iliotibial Tract MOB TCD

Movements of the Knee Joint

• Flexion and extension take place between the femoral condyles and the upper surface of the menisci

• Rotation occurs between lower surface of the menisci and upper surface of the tibia

MOB TCD

Extension Screw Home

• Contraction of the quadriceps results in extension

• The anterior cruciate becomes taut• And medial rotation of the femur

occurs around the taut anterior cruciate to accommodate the longer surface of the medial condyle

MOB TCD

Flexion

• Femoral condyles rotate medially around taut ACL during the locking mechanism of the knee

• Popliteus laterally rotates the femur to unlock the knee

• So flexion can occur • Then the hamstrings flex the

knee

MOB TCD

Functional Anatomy of Patellofemoral Joint (PFJ)

MOB TCD

Functional Anatomy of PFJ MOB TCD

Anterior and Posterior Cruciates

• Anatomically named by their tibial attachments

• Clinically femoral are called origin

• Covered by synovial membrane on anterior and on both sides which is reflected from capsule,

• I.e. oblique popliteal ligament• Bursa between them on lateral

aspect

anterior

lateral

MOB TCD

• Synovial membrane covers the anterior and sides of the cruciates

• Not covered on posterior aspect

Anterior and Posterior Cruciates Ligament

MOB TCD

• Anterior cruciate is attached to anterior aspect of the superior surface of the tibia behind

• Anterior horn of medial meniscus in front of the anterior horn of the lateral meniscus

• Passes upwards and laterally to the posterior aspect of medial surface of lateral femoral condyle

Anterior Cruciate MOB TCD

PCL

Anterior cruciate ligament

Posterior meniscofemoral ligament

Superior Aspect of Tibial Plateau Menisci

MOB TCD

• Three dimensional fan shaped• Multiple non-parallel interlacing

collagenous fascicles

Anterior Cruciate Ligament (ACL) MOB TCD

anterior

Anterior Cruciate Ligament MOB TCD

• Tibial attachment is in antero-posterior axis of tibia

• Femoral attachment is in longitudinal axis of femur

• Forms 40°with its long axis• 90°twist of fibres from extension

to flexion


• Anteromedial fibres have the most proximal femoral attachment

• Contribute to anteromedial stability

• Intermediate to straight and anteromedial

• Posterolateral aids in anteromedial stability


• ACL are vertical in extension

• 90°flexion are horizontal• PCL are more vertical in

90°flexion


• At 0°of flexion the fibres of the ACL are more vertical

• At 90°flexion they are in the horizontal plane

• Fibres of the PCL are more vertical with flexion and increasing flexion, > 90°becomes pivot

• PCL is least affective at 30°flexionHunziker et al 1992, Covey 2001

Cruciate MOB TCD

ACL in Extension and 45° MOB TCD

• PCL • Provides 94% of restraint

to posterior displacement

• ACL• Provides 86% of restraint

to anterior displacement

Anterior and Posterior Cruciate MOB TCD

• Middle genicular artery• Inferior medial genicular• Inferior lateral genicular

arteries via infrapatellar fat pad

• Only one main artery• Middle genicular enters

upper third

Anterior Cruciate LigamentBlood Supply

MOB TCD

• Strongest ligament• Shorter• More vertical• Less oblique• Twice as strong as ACL• Posterior

Posterior Cruciate MOB TCD

• PCL is the strongest ligament of the knee

• It is shorter • More vertical• Less oblique • Twice as strong as ACL • Closely applied to the

centre of rotation of knee• It is the principal stabiliser Hunziker et al.,1992


Attachment of PCL

• The tibial attachment of the PCL was on the sloping posterior portion of the tibial intercondylar area

• Anterior to tibial articular margin

• Blends with periosteum and capsule

• Extended 11.5-17.3 mm distal to the tibial plateau

Javadpour & O’Brien, 1992

MOB TCD

Frazer, 1965

Tibial Attachment of the PCL MOB TCD

• Anatomically the fibres pass anteriorly and medially and proximally

• It is attached on the antero-inferior part of the lateral surface of the medial femoral condyle

• The area for the PCL is larger than the ACL

• It expands, more on the apex of the intercondylar notch than on the inner wall

Hunziker et al.1992

.


• Three functional bands• Names vary • Anterior or anterolateral is larger• Central• Taut in flexion• Posterior or posteromedial taut in

extension• Posterior oblique bundleHunziker et al 1992

Posterior Cruciate Ligament MOB TCD

• Insertions of the PCL • Passes through four zones• Ligament• Fibrocartilage • Tidemark of mineralised

fibrocartilage • Bone in less than 1 mm Cooper & Misol, 1970; Fabbriciani & Oransky, 1992

Attachment of PCL MOB TCD

• Posterior oblique bundle• Most posterior fibres• Attached to posterosuperior part

of femur• Posterior medial part on

intercondylar area of tibia• Longest fibres• Tense in full extensionFredrick & O’Brien, 1992; Hunziker et al.,1992

Posterior Cruciate Ligament MOB TCD

• Proximal fibres on femur• Posterior fibres on the tibia are

longest• Undergo least change


• The PCL is located near the longitudinal axis of the knee

• Medial to the centre of the knee

• Vertical in frontal plane• 30°to 35°in sagittal• More horizontal in sagittal

with increased flexion


• PCL provides 94% of restraint to posterior displacement of the tibia

• Prevents external rotation of tibia more at 90°than at 30°

• ACL 86% of restraint to anterior displacement


Blood Supply of Cruciates MOB TCD

• Posterior cruciate is supplied by four branches

• Distributed fairly evenly over its course

• Subcortical vascular network at bony attachments

• Don’t contribute much to ligaments

Sick & Koritke, 1960

Blood Supply of Cruciates MOB TCD

• Main is middle genicular artery enters upper third of PCL

• Synovium surrounding PCL also supplies the PCL

• Contributions inferior medial, inferior lateral genicular arteries via infrapatellar fat pad

• Periligamentous and intra-ligamentous plexus• Very little from bony attachmentArnoczky 1987

Blood Supply of PCL MOB TCD

• Branches of tibial and obturator nerves

• Mechanoreceptors• Proprioceptive action

Posterior Cruciate Ligament Nerve Supply

MOB TCD

• Branches of tibial nerve• Middle genicular nerve • Obturator nerve (post)• Branches of the tibial nerve

enter via the femoral attachment of each ligament

• Nerve fibres are found with the vessels in the intravascular spaces

Nerve Supply of Cruciates MOB TCD

Mechanoreceptors

• Three types• Found near the femoral attachment• Around periphery• Superficially, but well below the

synovial lining.• Where maximum bending occurs• Ruffini endings• And ones resemble golgi tendon

organs• Paccinian• Proprioceptive function

MOB TCD

• Mechanoreceptors resembling golgi tendons

• Running parallel to the long axis of the ligament

• Found near the femoral attachment

• Around the periphery, where maximum bending occurs

• Posterior division of obturator nerve

Mechanoreceptors MOB TCD

• There is a gradual change in stiffness between the flexible ligamentous tissue and bone

• There is a transitional zone of fibrocartilage between collagen and bone

• This helps to prevent the concentration of stress at the attachment site

Beynnon, 2000; Hunziker et al.,1992

Posterior Cruciate LigamentBony Attachment

MOB TCD

Anatomy of Menisci

• Menisci are made of fibro cartilage

• Wedge shaped on cross section

• Medial is comma shaped with the wide portion posteriorly

• Lateral is smaller, two horns closer together round

• They are intracapsular and intra synovial

anterior

MOB TCD

• Anterior to posterior• Medial, anterior horn is

attached to the intercondylar area in front of the ACL and the anterior horn of the lateral meniscus

• Posterior horn of lateral, posterior horn of medial and PCL

• Medial is more fixed• Lateral more mobile

anterior

Anatomy of Menisci MOB TCD

• Medial is attached to the deep portion of medial collateral ligament

• Lateral is separated from lateral ligament by the inferolateral genicular vessels and nerve

• The popliteus, which is attached to lateral meniscus

• Posterior horn gives origin to meniscofemoral ligament


• Coronary ligaments are the portion of the capsule attached to the periphery of meniscus, which connects it to the tibia

• Synovial membrane, stops at the upper border of the meniscus

• Lines the deep aspect of the coronary ligament


• Blood supply at the periphery only

• Flexion and extension takes place at the upper surface of the menisci

• Rotation occurs between the lower surface of the menisci and the tibia

anterior


• Shock absorption • Redistributes forces• Spread synovial fluid • Minimal effect on stability • On rotation menisci move with femur • Lateral moves 20 - 24 mm • Medial less mobile 10 -15 mm • Lateral meniscus bears more load

Function of Menisci MOB TCD

Meniscofemoral Ligaments

• Anterior and posterior arise from posterior horn of lateral meniscus

• Anterior attached to femur anterior to PCL

• Posterior attached posterior to PCL• More variations in posterior

MOB TCD

• The Anterior meniscofemoral (Humphrey) is attached to lateral aspect of the medial femoral condyle in front of the PCL

• The posterior (Wrisberg) is attached posterior to the PCL

• The posterior meniscofemoral ligament is usually present

• Vary in size

Meniscofemoral Ligaments MOB TCD

Vessels and Nerves MOB TCD

Articular Fat Pads

• Increase with age• Compact lobules• With fibro-elastic interlobular septa• Septa well vascularised• Provide firmness, deformability and

elastic recoilWilliams & Warick,1980

MOB TCD

Infrapatellar Fat Pad (IFP)

• Superiorly • Fills the space between the inferior

pole of the patella• The ligamentum patella and deep

infrapatella bursa• Attached to intercondylar notch via

ligamentum mucosumWilliams & Warick,1980

MOB TCD

• Posteriorly • Covered by synovial

membrane• Forms alar folds• Femoral condyles• Intercondylar notch by

ligamentum mucosum• Attached to anterior

horns of menisci• Proximal tibiaWilliams & Warick,1980

Infrapatellar Fat Pad MOB TCD

• Blood supply inferior genicular arteries

• Also supply the lower part of the ACL from network of synovial membrane of fat pad

• Centre of fat pad limited blood supply

• Lateral arthroscopic approach to avoid injury

Kohn et al., 1995; Eriksson et al., 1980


• Can only expand anteriorly• Inflammation of IFP• Bulges on either side of patellar

tendon• Synovial membrane is compressed

by femoral condyles• Pain and inflammation


Clinical Conditions Affecting Infrapatellar Fat Pad

• Intrinsic• Hoffa’s disease• Intracapsular chondroma• Localised nodular synovitis• Post-arthroscopy / post-surgery fibrosis• Shear injury• Torsion

MOB TCD

Hoffa’s DiseaseFat Pad Impingement

• Hyperextension injury• Genu recurvatum and tilted inferior

pole of patella • Tenderness distal to patella• Beyond margins of the patellaBrukner & Khan, 2000; Garret et al., 2000

MOB TCD

Clinical Conditions Affecting IFP

• Anterior extra capsular disorders

• Patellar fracture• Patellar tendon rupture• Deep infrapatellar bursitis• Patellar tendonosis

MOB TCD

Osgood-Schlatter Disease Sinding-Larsen Johanssen Disease

Clinical Conditions Affecting IFP MOB TCD

Infrapatellar Fat Pad

• ACL repair with patellar tendon may result in fibrosis of fat pad and pain

• Delays rehabilitation• Inflammation of IFP may be process

leading to fibrosisMurakami et al., 1995

MOB TCD

Synovial Membrane MOB TCD

• The synovial membrane is very extensive

• It lines the inner aspect of the capsule and the non-articular structures inside the capsule, except posteriorly where it is carried forwards to cover the anterior and sides of the cruciate ligaments


• It covers the infrapatellar pad of fat, forming the alar folds

• The ligamentum mucosum is attached to the intercondylar notch at the apex of the alar fold

• The alar folds increase the surface area of the synovial membrane via the infrapatellar pad of fat,

• Which fill the changing spaces during movement of the joint and help to redistribute the synovial fluid


• The synovial membrane is continuous with:

• The suprapatellar bursa which extends a hand’s breadth above the patella. This bursa always appears distended when there is a haemarthrosis or traumatic synovitis in the knee joint

• Many other bursae, e.g. around the popliteus and under the medial head of the gastrocnemius


Plica

• A suprapatellar plica may separate the suprapatellar bursa from the synovial membrane of the knee joint

• Plicae folds may also be found on either side of the patella

MOB TCD

Bursa MOB TCD

Pathological Anatomy of AKP

Patellar Tendinitis / SLJ

Fat pad impingement

Infrapatellar Bursitis

Traction Apophysitis

Fractures & Instability

Patellofemoral syndrome

Prepatellar bursitis

Synovial plica

MOB TCD

Abnormal Lower Limb Biomechanics

• Anatomical anomalies • Femoral torsion• Genu valgum• Increased Q-angle • High (alta) patella• Tibial torsion• Overpronation

Q Angles

Males 140 Females 170

> 200 greater problems

MOB TCD

Knee Injuries

• Anterior cruciate tear• Bone bruising• Posterior cruciate tear• Osteochondritis• Synovial plica

MOB TCD

Traumatic• Meniscal tears• Ligament tears• Cruciates• Collaterals• Patellar dislocations• Fractures• Patella• Tibial plateau• Articular cartilage damage

Atraumatic

• Patellofemoral syndrome• Malalignment• Dislocations• Subluxations• Iliotibial band syndrome• Popliteus tendinopathy• Patellar tendinitis• Osgood-Schlatter’s• Fat pad impingement

Knee Injuries MOB TCD

O’Donoghue’s Triad

• Medial ligament tear• Anterior cruciate tear• Torn medial meniscus

MOB TCD

Mechanisms of Injury

• Valgus / External rotation • Posterior horn of medial meniscus

trapped by posterior condyles

MOB TCD

Osteochondritis MOB TCD

Meniscal Tears

• Medial meniscus has higher incidence but less morbidity • Traumatic tears• Twisting on a planted, flexed knee• Atraumatic tears• Degenerative wear and tear

MOB TCD

anatomy of Knee

Health & Medicine

Transcript of anatomy of Knee