KNEE JOINT ANATOMY

-DR.JEMI

INTRODUCTION

The structures around the knee have been classified in to three broad categories;

OSSEUS STRUCTURE

EXTRA ARTICULAR STRUCTURES

INTRA ARTICULAR STRUCTURES

OSSEOUS STRUCTURE

It consist of three components : the patella, the distal femoral condyle, and the proximal tibial plateaus or condyles.

The knee is called hinge variety of synovial type of joint.

THE DISTAL FEMORAL CONDYLE are two rounded prominances that are eccentrically curved. Anteriorly, the condyles are some what flattened, which creates a larger surface for contact and wt. transmission.

The groove found anteriorly between the condyles is the PATELLOFEMORAL GROOVE OR TROCHLEA. Posteriorly the condyles are seprated by intercondylar notch. The articular surface of the medial condyle is longer than that of the lateral condyle but lateral condyle is wider.

Long axis of lareral condyle – along the sagittal plane, medial condyle at 22-dgree angle to sagittal plane.

THE PROXIMAL END OF TIBIA forms two rather flat surfaces condyles or plateaus, that articulate with the femoral condyles. Separated in midline by intercondylar eminance with its medial and lateral intercondyler tubercles. Ant. & post. To intercondyler eminance are the areas that serves as attachment sites for the cruciate ligaments and menisci.

THE PATELLA – triangular sesamoid bone wider at proximal pole than distal pole.The articular surface divided by vertical ridge – smaller medial and larger lateral surface.In extension, the distal portion of lateral articular patella facet articulate with the lateral femoral condyle, but medial patellar facet barely articulates with the medial femoral condyle untill complete flexion is approched. During flexion extension the patella moves 7 to 8 cm in relation to the femoral condyle.

EXTRA ARTICULAR STRUCTURESConsists of SYNOVIUM, CAPSULE, COLATERAL LIGAMENTS, AND MUSCULOTENDINOUS UNIT PRINCIPALLY QUADRICEPS MECHANISM, THE GASTROCNEMIUS AND MEDIAL AND LATERAL HAMSTRING GROUPS, THE POPLITEUS, AND ILIOTIBIAL BAND.

QUADICEPS MECHANISM forms three layered quadriceps tendon that insert on patella.The tendon of rectus femoris – ant. Layer, inserts at the ant. Edge of proximal pole.The tendon of vastus intermedius – deepest layer, inserts at post. Edge of proximal pole.The vastus medialis and vastus lateralis – middle layer.The fiber of medial retinaculum – formed from the aponeurosis of the vastus medialis- inserts side of patella- prevent lat. Displcement.Patella tendon – origin distal pole of the patella – inserts in to the tibial tuberosity.

The gastrocnemius – the most powerful calf muscle, span post. Aspect of knee in intimate relationship with post. Capsule, inserts on post. Aspect of , medial and lateral femoral condyles.

Pes anserinus – conjoined insertion of the sartorius, gracilis, and semitendinousus muscles along proximal medial aspect of tibia. Primary flexors of knee and secondery intrenal rotational influence on tibia. protect knee- valgus and rotatory stress.

The biceps femoris – counterpart of pes anserinus on lat. Side of knee insert into fibular head, lateral tibia, and postlat.capsular structers. Provide varus and rotatory stability.

The iliotibial band – post 3rd of ITB inserts proximally into the lateral epicondyle of femur and distally into lateral tibial tubercle (gerdy tubercle)

Popliteus muscle- has three origin 1) lat. Femoral condyle 2) fibula{popliteofibular ligament} 3) post. Horn of lateral meniscus.Femoral and fibular origin – forms arm of oblique Y shaped ligament joined by capsule and meniscal origin.Prime medial rotator of tibia during flexion.

MEDIAL AND POSTEROMEDIAL CORNER OF THE KNEE STABILISER

STATIC - JOINT CAPSULE DYNAMIC -SUPERFICIAL MCL -PES ANSERINUS -DEEP MCL -SEMI MEMBRANOSUS - POSTERIOR OBLIQUE LIG. -MEDIAL HEAD OF GASTROCNEMIUS -VASTUS MEDIALIS

MARSHELL AND WARREN - THREE LAYERS OF MEDIALCAPSULER LIGA.STRUCTURE

LAYER-1:SUPERFICIAL FACIA LAYER-2:SUPERFICIAL MCL LAYER-3THAT INVESTS SARTORIUS PARELLEL FIBERS AND OBLIQUE DEEP MCL - MENISCO&QUDR. PROXIMLLY FIBERS. FEMORAL & MENIS-WITH PES ANSERINUS & COTIBIAL PART.PERIOSTEUM PROXIMALLY.

THE CAPSULE: IT IS SLEEVE OF FIBROUS TISSUE EXTENDING FROM THE PATELLA & PATELLA TENDON ANT. TO MED, LAT, POST, EXPANSION OF JOINT.

CAPSULE AND MED & LAT EXTENSOR EXPANSION OF POWERFUL QUEDS. ARE PRINCIPLE STABILIZING STRUCTURE ANT. TO TRNSVERSE AXIS OF JOINT.THE CAPSULE IS REINFORSED BY COLLATERAL LIGA. , MED & LAT HAMSTRING MUSCLE AS WELL AS BY POPLITEUS & ITB POST TO TRANSVERSE AXIS.

ANTMEDIALLY CAPSULE REINFORSE BY MED RETINACULUM EXPANSION, MPFL & PATELLOTIBIAL LIGA.ANTLATERALLY CAPSULE RENFORSE BY LAT EXPANSION OF RETINACULUM & ITB.

THE MCL – long narrow superficial to medial capsule & capsular ligamentous structure, originating on the medial femoral epicondyle and inserting 7 to 10 cm below the joint line on post. Half of med. Surface of the tibia metaphysis deep to the pes anserinus tendon. DEEP MCL: REINFORCE MIDMEDIAL CAPSULE , ORIGINATED FROM MED FEMORAL EPICONDYLE AND INSERTED ON JUST BELOW THE TIBIAL ARTICULAR MARGIN.

-IT PROVIDES THE PRINCIPAL STABILITY TO VALGUS STRESSES.

ANTERIORLY – layer 2 &3 –discretePOSTERIORLY – layer 2&3 merge to form posteromedial corner.

HUGHSTON AND EILERS described a discrete anatomic structure in the posteromedial capsule called POSTERIOR OBLIQUE LIGAMENT (POL), a thickning of the capsular liga. Attached proximally to adductor tubercle of femur and distally to tibia and post aspect of the capsule. POL THREE ARMS

TIBIAL ARM- ATTACHES SUPERIOR OR CAPSULAR SUPERFICIAL ARM- CLOSE TO POST ARTICULAR ARM-WHICH IS CONTINUOS POORLY DEFINEDSURFACE OF TIBIA. WITH THE POST CAPSULE AND WHICH ATTACHES TO BLEND WITH THE OBLIQUE SEMI M. TENDON AND POPLITEAL LIGAMENT TIBIA.

SEMI MEMBRANOSUS FIVE EXTENSION IN TO POSTMEDIAL CORNER AND CAPSULE1)PARS REFLEXA PASSING BENEATH MCL & INSERTING ON TIBIA2)POSTMEDIAL TIBIAL INSERTION 3)THE OBLIQUE POPLITEAL LIGAMENT INSERTION 4)EXPANSION TO POL5)POPLITEAL APONEUROSIS EXPANSION

KEY POINTSSUPERFICIAL AND DEEP MCL ALONG WITH POSTMEDIAL STRUCTURE WORK IN COORDINATION TO PROVIDE STABILITY- VALGUS AND EXT.ROTATION STRESS.

SUPERFICIAL LIGA. PRIMARY STABILISER AGAINST VALGUS & ER –THEN AFTER DEEP MCL & POL.

QUDRICEPS MOST IMP FOR PROTECTION IN VALGUS STRESS.

KNEE FLEX –SEMI M. CONTRACTS TENSING THREE ARMS OF POL PROVIDING BOTH KINETIC AND STATIC STABILISING EFFECT.

CONTACT SEMI M. TENSE TIBIAL ARM OF POLRETRECT POST. HORN OF MED.MENISCI PREVENT IMPINGMENT OF MENISCUS AS THE KNEE FLEX.

LATERAL AND POSTERO LATERAL CORNER OF KNEEANATOMY IS COMPLEX AND VARIABLE. A) ILIOTIBIAL BAND - Extends proximally from its main distal insertion on Gerdy tubercle composed of four main

structures.

1)Main componant – superficial layer covers large portion of the lat. knee & is the 1st layer encuntered after dissecting through the subcutaneous tissue of lateral knee

2)Iliopatellar band – ant. Expansion of superficial layer attach to lat. Border of patella & are IMP IN PATELLOFEMORAL TRACKING.

3)Deep layer- attaches the medial aspect of superficial layer to distal aspect of lat. Inter muscular septum.

4)capsulo-osseous layer- it begins proximally from region distal lateral intermuscular septum & blends with confluence of facia from short head of biceps femoris & lateral gastrocnemius tendon. This capsulo-osseous layer and deep layer extends distally to attach to ant.lat. Aspect of tibia just post & proximal to gerdy tubercle

CLINICAL SIGNIFICANCE – 2ND STABILISER OF LAT SIDE OF KNEE PX VARUS OPENING OF THE KNEE

B) FIBULAR OR LATERAL COLLATERAL LIGAMENT- primary static stabiliser to varus - Proximal attachment site located in small bony depression slightly proximal &

postto lat. Femoral epicondyle. 1.4mm proximal & 3.1 mm post to lat femoral epicondyle.

- Distally on to head of fibula at the apex of superior &lateral – facing V shaped platue. An avg. 8.2mm post to ant. Aspect of fibular head & 28.4mm distal to fibular styloid process.

- Avg. length 70mm

C) POPLITEUS MUSCLE – TENDON COMPLEX & POPLITEOFIBULAR LIGAMENT- Provide both static & dynamic stability to postlat. Aspect of knee.- Origin: broad muscle insertion at pos.med. Surface of proximal tibia metaphysis.- Insertion: proximally main tendon attachment is at the proximal half ant 1/5th of

popliteus sulcus of femur about 18.5mm ant. & inferior to femoral insertion of FCL.

- Three popliteomeniscal fecicles – ANT.INF, POST.SUP, POSTINF.- Politeo fibular ligament- originates from popletius muscle-tendon complex. - two division – ant. & post. Forms inverted Y . Ant. Division attaches to the down

slope of ant.med. Aspect of fibular styloid process. Post. Division attaches to the apex and downslope of postmed. Fibular styloid process & provide more stability.

• -coronary ligament – distal to the musculotendinous junction of popliteous muscle a broad aponeurotic attachment extend to attach to post.lat. Capsule & post horn of lat. Meniscus, cinically- reinforce and stabilize the lat meniscus and post. Knee capsule.

D) Long and short head of biceps femoris- - two head of origin, long head tuberosity of ischium and sacrotuberous lig. - Short head from lateral lip of the linea aspera between adductor magnus and

vastus lateralis.- The tendon of insertion of this muscle forms the lateral hamstring & inserted

into lat. Side of head of fibula; the common peroneal nerve descend along its medial border.

• - Both long and short head of biceps femoris prove static and dynamic stability to lat and PLC of knee.

• E)Additional structure-- Mid third lat capsular liga, is a thickning of lat capsule, two parts

• Menisco femoral menisco tibial• extend from lat meniscus to lat meniscus to the tibia just post anchorage just post to to gerdy’s tubercle- Lat femoral epicondyle.

-Fabellofibular ligament – distal edge of capsule arm of short head of biceps femoris , it inserts along the lat. Edge of fabella & attaches just lat to fibular styloid.

-KEY POINTS :-POST.LAT & LAT. STRUCTURES ACT IN COMBINATION WITH CRUCIATE LIGAMENTS TO PROVIDE OVERALL STATIC & DYNAMIC STABILITY TO LAT. KNEE.

-THESE STRUCTURES FUNCTION PRIMARILY TO RESIST VARUS ROTATION & POST LAT TIBIAL ROTATION, SECONDARY STABILISER TO ANT. POST. TIBIAL TRANSLATION & IR STABILITY TO TIBIA.

INTRA ARTICULAR STRUCTURES

THE PRINCIPLE INTRAARTICULAR STRUCTURES ARE- MEDIAL AND LATERAL MENISCI AND ANTERIOR AND POSTERIOR CRUCIATE LIGAMENTS.

MENISCI FUNCTION AND ANATOMY: -FUNCTIONS:-Act as a joint filler, compensating for gross incongruity between femoral and tibial articular surfaces.-They prevent capsular & synovial impingment during flexion and extension.-Joint lubrication function-Distribute synovial fluid through out the joint and aiding the nutrition of articular cartilage.-Provide stability in all plane but are especially imp. Rotatory stabilizer.-Shock absorption -Loadbearing or weight bearing function.

ANATOMY:- The menisci are crescents ,roughly triangular in cross section that cover half to

one third of articular surface of tibia.

- They are composed of dense tightly woven collagen fibers arranged in a circumferential and radial pattern providing great elasticity and ability to with stand to compression.

- Peripheral edge- convex, attached to the inner surface of joint capsule except where the popliteus is interposed laterally, also attached to the border of the tibial plateau by coronary liga.

- Inner edge- concave, thin unattached.

- The menisci are largely avascular except near their peripheral attachment.

- Inferior surface is flat where as the sup. Surface is concave corresponding to the femoral condyle.

Medial meniscus -C shaped, larger diameter, thinner periphery, narrower body, post horn wider than ant.

-Ant horn- attach to tibia ant to inter condylar eminance

-POST. Horn- attach in front of PCL post. To the inter condylar eminance .

-Entire peripheral border is firmly attached to medial capsule & coronary ligament

-Does not attach either of cruciate liga.

Lateral meniscus-More circular, more mobile than MM , smaller in DM , thicker periphery, wider body.

-Ant horn – attached to tibia medially in front of intercondyler eminance.-Post horn – insert in to the post. Aspect of intercondylar eminance in front of post attacment of MM.

-Post horn receive anchorage to femur by ligament of wrisberg and liga. Of humphery & from facia covering the popliteus , arcuate complex at post.lat. Corner of knee.

-The tendon of the popliteus seprate the post.lat. Periphery of lat meniscus from joint capsule.

KEY POINTS:

- THE MENISCI FOLLOW THE TIBIAL CONDYLE DURING FLEX-EXT, BUT DURING ROTATION THEY FOLLOW THE FEMUR MOVE ON TIBIA.

- ITS ANT AND POST ATTACHMENT FOLLOW THE TIBIA BUT ITS INTERVENING PART FOLLOW THE FEMUR THUS ITS LIKELY TO BE INJURED DURING ROTATIONS.

- LATERAL MNISCUS FIRMLY ATTACHED TO THE LIGA. WRISBERG & HUMPHERY AND POLITEOUS TENDON FOLLOWS THE LATERAL FEMORAL CONDYLE DURING ROTATIONS & THEREFORE IS LESS LIKELY TO BE INJURED .

- ARNOCZKY AND WARREN SHOWED THAT THE VASCULAR SUPPLY TO M.M & L.M. ORIGINATES PREDOMINANTLY FROM LAT. AND MED. GENICULAR VESSELS BOTH INF. AND SUP.BRANCHES FROM THESE VESSELS GIVE RISE TO PERIMENISCAL CAPILLARY COMPLEX THAT SUPPLIES THE PERIPHERAL BORDER OF MENISCUS.

- THREE ZONE OF MENISCAL VASCULARITY 1.RR- RED-RED IS FULLY WITHIN VASCULAR AREA 2.RW, RED-WHITE ZONE IS AT BORDER OF VASCULAR AREA 3. WW, WHITE-WHITE ZONE IS WITHIN AVASCULAR AREA.

ANTERIOR CRUCIATE LIGAMENT(ACL)- ORIGINATES- from medial wall of lateral femoral condyle –course ant. & med. Across the

knee joint insert on tibial articular surface consist of anteromedial & posterolateral bundle after their tibial insertion on on the tibial plataue , medial to the insertion of ant. Horn of L.M. ant.lat to the ant. Tibial spine.

- Primary role – provide stability against ant. Translation of tibia.- Secondery role – rotatory stability

- Length – 31-35mm & 31.3mm2 in cross section.

- Pathology – composed of bundle of type-3 collagen fibril ensheathed by connective tissue called enotendineum, together called subfacicular unit.this unit surrounded by another layer of connective tissue called epitendineum and whole unit called faciculus. Faciculus surrounded by pera tendon.

- Blood supply- middle genicular artery & inf med and lat. Genicular artery both are branch of popliteal artery.

- Innervation- post. Articular nerve branch of tibial nerve.

POSTERIOR CRUCIATE LIGAMENT(PCL)- Technically its extra articular structure.- Synovium that reflect from post. Capsule surround ant. Med. Lat. Side

where as post. Border of PCL intimate with capsule and periosteum.- ATTACHMENT

TIBIA FEMORAL LAT TO MED ON TIBIA ADJUSCENT TO ANT. CARTILAGE AT FOVEA ABUOT MARGIN OF MED FEMORAL 1-1.5 CM BELOW CONDYLE IN ANT-POST JOINT LINE. DIRECTION.

PCL COMPONANT

ANTEROLTERAL BUNDLE POSTEROMEDIAL BUNDLE MENISCOFEMORAL LIGA.Taut in flexion Taut in extension & deep flexion ANT. LIG. POST OF HUMPHERY WRISBERG BOTH ARISE FROM POST HORN L.M. SANDWITCH PCL ANT& POST

AVG. LENGTH – 32-38 MM

CROSS SECTION AREA 31.2MM

BLOOD SUPPLY : MIDDLE & INF. GENICULAR ARTERY

INNERVATION : POSTERIOR ARTICULAR NERVE.

PROVIDE PRIMERY STABILITY TO POST. TRANSLATION OF TIBIA & ER.

SUMMERY:

VARUS STABILITY- PRIMARY BY LCL & SECONDARY BY PCL

VALGUS STABILITY- PRIMARY BY MCL & SECONDARY BY ACL

AGAINST ANT TIBIAL TRANSLATION – ACL

AGAINST POST TIBIAL TRANSLATION- PCL

IR – PRIMARY BY ACL SECONDARY BY PLC

ER- PRIMARY BY PCL SECONDARY BY PMC

POPLITEAL ARTERY: - IS DEEPLY PLACED CONTINUATION OF FEMORAL ARTERY . IT COURSE THROUGH THE POPLITEAL FOSSA AND ENDS AT LOWER BORDER OF THE POPLITEUS MUSCLE WHERE IT TERMINATE IN TO ANT & POST TIBIAL ARTERY.

RELATIONS:ANT: THE POPLITEAL SURFACE OF THE FEMUR, THE KNEE JOINT, POPLITEUS MUSCLE.POST : POPLITEAL VEIN, TIBIAL NERVE, FASCIA AND SKIN.

POPLITEAL ARTERY

SUP GENICULAR ARTERY MIDDLE GEN. ART. INF. GENI ARTERY

MED .SUP LAT .SUP MED.INF LAT.INF

- MIDDLE GENICULAR ART. PROVIDE MAJOR BLOOD SUPPLY TO CRUCIATE LIG AND POST CAPSULE & SYNOVIUM.

- MED.SUP.GEN. RUNS IN FRONT OF SEMI.M & SEMI.T ABOVE MED HEAD OF GASTROCNEMIUS.

- LAT.SUP.GEN. - PASSES ABOVE THE LAT CONDYLE OF FEMUR BENETH THE TENDON OF BICEPS FEMORIS.

- MED.INF.GEN.- FIRST DESCEND ALONG THE UPPER MARGIN OF POPLITEUS, THEN PASSES BELOW THE MED TIBIAL CONDYLE BENEATH THE MCL, AT ANT BORDER OF WHICH IT ASCEND IN FRONT AND MED SIDE TO SUPPLY KNEE JOINT & UPPER END OF TIBIA.

- LAT.INF.GEN. - RUNS LATERALWARDS ABOVE THE HEAD OF THE FIBULA TO THE FRONT OF KNEE JOINT PASSING IN ITS CORSE BENEATH THE LAT. HEAD OF GASTROCNEMIUS FCL & TENDON OF BICEPS FEMORIS.

THANK YOU