Knee Joint Anatomy PDF

Proximal End of the Tibia Consists of: • Lateral and medial condyles of the tibia • Two flattened boney masses • Not rounded like the femur • Overhang the shaft of the tibia • Articular surface is located superiorly • Broad oval shape • Clinically, the superior surface is often referred to as the...

Proximal End of the Tibia Consists of: • Lateral and medial condyles of the tibia • Two flattened boney masses • Not rounded like the femur • Overhang the shaft of the tibia • Articular surface is located superiorly • Broad oval shape • Clinically, the superior surface is often referred to as the tibial plateau • Tibial tuberosity • Large triangular shaped boney prominence anteriorly • Apex points inferiorly Tibial Tuberosity • Insertion site of the patellar ligament • Lateral border Tibial tuberosity MC LC Tibial tuberosity MC • Sharp, distinct • Continuous with sharp anterior border of tibial shaft • Strongest attachment site for the patellar ligament • Epiphyseal line divides the tuberosity into two regions • Superior – smooth • Deep infrapatellar bursa • Inferior – rough Right Tibia Anterior border • Subcutaneous • Contacts the ground when kneeling Medial Tibial Condyle Superior view right tibia • Larger than the lateral tibial condyle • Bears 60% of the weight Medial condyle • Larger articular facet Intercondylar eminence, medial and lateral tubercles • Oval in shape • Longest in the AP direction • Medial femoral condyle is longer and narrower • Shallow concavity • Deepened by the medial meniscus • Extends onto the medial tubercle of the intercondylar eminence groove • Groove for insertion of semimembranosus • Hamstring muscle Posterior view, right Lateral tubercle of the Intercondylar eminence Lateral Tibial Condyle Medial tubercle • Smaller than the medial condyle • But overhangs the shaft to a greater extent • Articular surface (facet) is also smaller Gerdy’s tubercle Lateral facet Gerdy’s tubercle • Located superiorly • Round in shape • Extends onto the lateral tubercle of the intercondylar eminence • Gerdy’s tubercle • Flattened area for insertion of iliotibial band (IT band) • Anterior aspect Fibular facet • Fibular facet • Posterior aspect, under the overhang • Not part of the knee joint • Groove for popliteus tendon Right Tibia • Superior to the fibular facet Intercondylar Area of the Tibia Lateral meniscus posterior horn PCL Medial meniscus posterior horn • Non-articular area between the two articular facets • Intercondylar eminence • Boney prominence in the center • Medial and lateral tubercles • Narrowest part of the intercondylar area Medial facet Lateral facet • Slopes downward from the eminence anteriorly and posteriorly • Attachment site for: ACL Lateral meniscus anterior horn Tibial tuberosity Medial meniscus anterior horn • Anterior and posterior cruciate ligaments • Horns of the medial and lateral menisci Superior Aspect of the Tibia Lateral meniscus posterior horn PCL Medial meniscus posterior horn • Intercondylar area • PCL is the most posterior attachment • Anterior horn of the medial meniscus is the most anterior attachment Middle facet Lateral facet • Synovial membrane attachment ACL Lateral meniscus anterior horn Tibial tuberosity Medial meniscus anterior horn • Attaches to the bone at the edges of the facets and bone in the intercondylar area • Creates 2 spaces • Envelops the cruciate ligaments Fibrous Capsule of Knee Joint • The fibrous capsule is deficient anteriorly • Reinforced by ligaments Fibrous Intercondylar line • Medially, laterally and posteriorly • Attaches along the margins of the articular surfaces of the femur, patella and tibia except: • Anteriorly, it extends superiorly and inferiorly • Posteriorly, its attached to the intercondylar line of the femur Fibrous Posterior right knee Fibrous Joint Capsule • What replaces the fibrous joint capsule anteriorly? • Inferior part of quadriceps tendon • Patellar ligament • Medial and lateral patellar retinacula • Extend from the side of the patella • Travel inferoposteriorly to blend with the respective collateral ligament • Reinforced anterolaterally by the iliotibial band insertion Quadriceps tendon IT band Medial patellar retinaculum Lateral patellar retinaculum Patellar ligament • Gerdy’s tubercle Anterior right knee Coronary Ligaments of Fibrous Joint Capsule • Deep parts of the fibrous joint capsule • Attach the inferior edges of the menisci to the periphery of the tibial plateau • Meniscotibial ligaments • “coronary” = crown Medial Extrinsic (Extracapsular) Ligaments of the Knee Joint • Anteriorly • Patellar ligament • Continuation of quadriceps tendon • Strong, flattened band from apex of patella to tibial tuberosity • Sides of the joint • Medial (tibial) collateral ligament (MCL) • Lateral (fibular) collateral ligament (LCL) • Posteriorly: • Popliteal ligaments IT band MCL LCL Patellar ligament Oblique Popliteal Ligament • Expansion of the tendon of the insertion of semimembranosus Joint capsule attachment at intercondylar line Tendon of adductor magnus • Hamstring muscle located medially in posterior thigh • Attachments • Posterior medial condyle of tibia • Posterior aspect of the lateral condyle of femur, intercondylar line • Reinforces the joint capsule posteriorly Tendon of semi membranosus Oblique popliteal ligament Joint capsule attachment Posterior right knee: Arcuate Popliteal Ligament Shaped like a “Y” • Stem attaches to the head of the fibula • Two arms attach to: • Lateral epicondyle of the femur • Often absent, poorly developed • If present, blends with lateral head of gastrocnemius Arcuate popliteal ligament • Posterior intercondylar area • More constant of the two • Passes superficial to the tendon of popliteus muscle • Arcuate and oblique popliteal ligaments help to prevent hyperextension of the knee Popliteus muscle, cut Head of the fibula Medial (Tibial) Collateral Ligament (MCL) • Broad, flat ligament • Attachments: • Medial epicondyle of femur • Medial condyle of tibia MCL • Extending onto the medial shaft LCL • Blends with the capsule and medial meniscus posteriorly • If you tear your MCL, it’s common to also tear the medial meniscus • The ACL may also tear, creating an “unhappy triad” of injuries Tendon of semimembranosus Biceps femoris tendon Lateral (Fibular) Collateral Ligament (LCL) (MCL) (LCL) • Strong, rounded cord-like ligament • Does not blend with the capsule or lateral meniscus • About 5 cm long • Palpable • Attachments: • Lateral epicondyle of femur • Head of the fibula Anterior view left knee Collateral Ligaments of Knee • Provide additional stability to the knee joint • Prevent side to side movements of the tibia and femur relative to one another • Permit more movement during flexion than extension • More posterior location • Tight during extension • Relatively loose during flexion Anterior view left knee Left posterior knee Popliteus Muscle • Proximal attachment (origin): Posterior MFL Popliteus tendon Anterior MFL • Inferior to lateral epicondyle of femur • Lateral meniscus, posteriorly • Travels • Deep to the LCL • Deep to arcuate popliteal ligament • Inside the fibrous knee joint capsule Popliteus • Distal attachment (insertion): • Posterior surface of tibia • Superior to soleal line Popliteus Muscle Right posterior knee LCL • Action: • Medial rotation of the tibia • When non weight-bearing (NWB) • “Unlocks” the extended knee at the beginning of knee flexion • Pulls posteriorly on the lateral meniscus Arcuate popliteal ligament Popliteus muscle, cut • Prevents meniscus from slipping anteriorly and getting caught between the articular surfaces Lateral View of the Left Knee LCL Posterior Right Knee Joint PCL MM LM Popliteus Capsule and synovial membrane removed Synovial Membrane of Knee Joint • Quite extensive and complex • Continuous with several bursae • Divides the knee joint into two separate synovial cavities posteriorly • Does not attach to: • Articular surfaces of bones • Superior and inferior surfaces of menisci • Patellar ligament • Posterior surfaces of ACL, PCL Lateral femoral condyle ACL, PCL Medial femoral condyle Lateral meniscus Medial meniscus patella Fat pad deep to synovial membrane Synovial Membrane of Knee Joint What does it attach to? Quadriceps tendon and femur • Inner surface of the fibrous joint capsule ACL, PCL (sides & anteriorly) • Anterior surface of femur • Margins of the articular surfaces • Infrapatellar fat pad Synovial membrane attaching to intercondylar fossa • Including the deep surface of quadriceps tendon • Located deep to patellar ligament • Outermost edges of the two menisci • Superiorly and inferiorly • Intercondylar notch of the femur • Sides and anterior aspect ACL, PCL • Intercondylar area of tibia Synovial membrane lining the infrapatellar fat pad Synovial Membrane Formations of Knee Joint Suprapatellar bursae • Ligamentum mucosum • Central fold of synovial membrane • From the infrapatellar fat pad to the intercondylar notch of the femur • Partially separates the right and left sides of the joint posteriorly • ACL and PCL are extrasynovial • Not in the synovial cavity • But they are within the knee joint capsule Subpopliteal recess Ligamentum mucosum Alar folds Synovial Membrane Formations of Knee Joint Suprapatellar bursa • Alar folds (plicae) Popliteus tendon • Folds of synovial membrane coming off the patella • Suprapatellar (recess) bursa • Between the femur and the quadriceps femoris tendon • Most superior recess of the synovial cavity • Not a true bursa • Subpopliteal recess • At posterolateral aspect of the knee joint • Separates the tendon of popliteus from the lateral tibial condyle Subpopliteal recess Ligamentum mucosum Alar folds (plicae) Sometimes the plica located in the middle of your knee becomes irritated. This is called plica syndrome and it's characterized by pain, swelling and instability Medial patellar retinaculum IT band reinforces capsule anteriorly as it overlies the lateral patellar retinaculum Plica Syndrome Left Knee Alar fold Alar fold (Alar fold) Right knee Alar fold One Synovial Cavity of the Knee Joint Two synovial cavities posteriorly: Suprapatellar bursa Cavity Cavity Subpopliteal recess Cruciate ligaments not lined by synovial membrane posteriorly Posterior Lateral Synovial Membrane • Lines the superior aspect of the infrapatellar fat pad (body) • The fat pad is extrasynovial but intracapsular • Articularis genu • Muscle that attaches to the most superior part of the synovial membrane • Suprapatellar recess • Functions to tighten the synovial membrane Popliteal (Baker’s) Cyst • Abnormal synovial fluid filled sac in the popliteal fossa • Almost always due to a chronic joint effusion (increased fluid in the joint)from injury/overuse • Herniation of synovial membrane and synovial fluid thru the posterior fibrous joint capsule • Connected to the rest of synovial cavity by a narrow stalk Intracapsular Ligaments of Knee Joint • Lie inside (within) the fibrous joint capsule • Anterior and posterior cruciate ligaments • Transverse ligament • Anterior and posterior meniscofemoral ligaments Cruciate Ligaments • Named for their location on the tibia: • Anterior cruciate ligament (ACL) • Posterior cruciate ligament (PCL) • Shorter and stronger • Cruciate means cross • ACL and PCL form an “X” as they cross one another • Very strong • Limit sliding movements between the tibia and femur • Prevent anterior and posterior sliding of tibia and femur • Intracapsular but extrasynovial • Lined by synovial membrane anteriorly, medially and laterally • Not posteriorly ACL PCL Anterior Cruciate Ligament ACL • Attachments: • Anterior intercondylar area of the tibia, medial aspect • Located between the anterior horns of the two menisci • Lateral condyle of the femur • Lateral wall of the intercondylar notch Posterior Cruciate Ligament PCL • Attachments: • Posterior intercondylar area of the tibia • Posterior to the attachments of both posterior horns of the menisci • Medial femoral condyle • Anterior aspect of the medial wall of the intercondylar fossa • Shorter and stronger than the ACL Transverse Ligament of the Knee PCL MCL ACL Tendon of popliteus LCL Transverse ligament of the knee • Joins the anterior horns of the two menisci • Quite variable in thickness • Often absent Meniscofemoral Ligaments of Knee Anterior meniscofemoral ligament • Also variable • Rarely are both present • Attach the lateral meniscus to the femur • Act to pull the posterior horn anterior and medially, increasing the fit • Posterior meniscofemoral ligament • From posterior horn of lateral meniscus to medial condyle of femur (medial wall of intercondylar fossa) • On the posterior surface of PCL • Anterior meniscofemoral ligament Posterior meniscofemoral ligament • Similar attachments, but travels anterior to PCL Menisci of the Knee Joint • Fibrocartilaginous discs attached to the tibia by • Anterior and posterior horns • Coronary ligaments (part of fibrous capsule) Patellar ligament ACL Medial meniscus • Each covers about 2/3s of the articular surface of the tibia AH • Increases depth of tibial articular surfaces • Internal free edge is thinner and bathed in synovial fluid PH LCL MCL PCL Lateral meniscus Superior view right tibia Lateral Meniscus • Round, nearly a complete ring • Wider than medial meniscus • Covers more surface area • Attached to the joint capsule • Posterior horn may be attached to the femur • Not attached to lateral (fibular) collateral ligament • Due to popliteus tendon traveling between the LCL and knee joint • Popliteus also attaches to the lateral meniscus Lateral Meniscus Synovial membrane has been removed medially: Attachments to the lateral meniscus: 1. Popliteus 2. Meniscofemoral ligs, if present 3. Fibrous joint capsule 4. NOT LCL Medial Meniscus • C-shaped • Wider posteriorly • Attached to both the joint capsule and the tibial collateral ligament medially • Anterior horn is the most anterior structure that is attached to the intercondylar surface of the tibia Meniscal Injury • Medial meniscus is more likely to tear • Lateral meniscus is less likely to tear due to its mobility • Symptoms: • Pain with medial rotation of the tibia • Indicates injury of the medial meniscus • Pain with lateral rotation of the tibia • Lateral meniscus injury Unhappy Triad of the Knee • Mechanism of injury • Blow from the lateral side while foot is fixed • Sudden twisting of the knee with foot fixed • Structures injured: • 1. Torn MCL • 2. Torn medial meniscus • 3. Torn ACL • Why? • Due to the firm attachment of the structures to one another Numerous Bursae of the Knee Joint Deep to heads of gastrocnemius Deep to Semimembranosus tendon Deep to LCL Anterior bursae of the knee joint Superficial to LCL Deep to biceps femoris tendon Deep to pes anserinus (3 tendons) Anterior Bursae of the Knee Joint • Suprapatellar recess (bursa) • Usually not a true bursa • Quite large • Superficial (subcutaneous) prepatellar bursa • Between the patella and the skin • Superficial (subcutaneous) infrapatellar bursa • Between the tibial tuberosity and the skin • Deep infrapatellar bursa • Between superior aspect of tibial tuberosity and the patellar ligament • Pretty small BURSITIS • Bursitis of the subcutaneous prepatellar bursa • Commonly known as “housemaid’s knee” Blood Supply to the Femur • Usually only one nutrient artery 2nd perforating artery Profunda femoris artery Femoral artery • Enters the femur posteriorly • Usually a branch of the 2nd perforating artery • Blood supply to the distal end of the femur is extensive • Genicular anastomosis • Unlikely to have death (necrosis) of bone from fractures in this area • Blood supply to the proximal end of the femur is more precarious Genicular anastomosis • Can be disrupted in fractures of the femoral neck • May lead to necrosis of the femoral head Blood Supply to the Knee Joint • 10 arteries supply the knee joint • 9 of them form the genicular anastomosis • 2 of the 9 are descending branches from the thigh: • Descending branch of lateral circumflex femoral artery • Branch of profunda femoris artery • Descending genicular artery Descending genicular artery • Branch of the femoral artery Blood Supply to Knee Joint • Popliteal artery • Continuation of the femoral artery • Passes from the anterior thigh to the posterior knee (popliteal) • Thru the adductor hiatus (opening in adductor magnus) • Middle genicular artery • Not part of the anastomosis • Pierces the fibrous layer of the joint capsule posteriorly • Supplies the cruciate ligaments, synovial membrane, periphery of the menisci • Branch of the popliteal artery Genicular Arteries Posterior view: • Branches of the popliteal artery Superior lateral genicular artery Superior medial genicular a. Popliteal artery Inferior lateral genicular artery Anterior tibial artery Inferior medial genicular a. • Superior medial genicular a. • Supply medial aspect of knee joint and femur • Located just proximal to the medial condyle • Inferior medial genicular a. • Supplies medial aspect of knee joint and tibia • Superior lateral genicular a. • Supplies lateral aspect of knee joint and the femur • Located just proximal to lateral • Inferior lateral genicular a. Posterior tibial a. • Supplies lateral knee joint Inferior Genicular Arteries • Travel deep to the collateral ligaments of the knee • Inferior lateral genicular artery Posterior view left knee • Travels superficial to popliteus muscle Anterior view left knee Popliteus • Inferior medial genicular artery • Supplies popliteus muscle Descending branch of lateral circumflex femoral artery Femoral artery Descending branch Genicular Anastomosis • Remaining 3 arteries are branches of the tibial arteries: Popliteal artery • Anterior and posterior recurrent tibial arteries • Branches of anterior tibial a. • Circumflex fibular artery Circumflex fibular artery • Branch of posterior tibial a. • Travels around the neck of the fibula • Genicular arteries anastomose with Anterior tibial recurrent artery Posterior tibial artery Anterior tibial artery • Artery just proximal • Artery just distal • Contralateral genicular artery anteriorly Movements at the Knee Joint Tibiofemoral portion: • Bicondylar synovial joint • Flexion/extension • Transverse axis • Movement in the sagittal plane • Lateral/medial rotation • Longitudinal axis • Movement on the transverse plane • Lateral/medial conjunct rotation • Accompany flexion and extension Muscles that Move the Knee Joint • Hamstrings • Posterior compartment of the thigh • Action: flexion of the knee • Origin: • Ischial tuberosity • Insertion: • Tibia • Medial group (semimembranosus) • A: medial rotation of knee • Fibular head • Lateral group • A: lateral rotation of knee Hamstrings Muscles that Move the Knee Joint • Quadriceps femoris • Anterior compartment of the thigh • Action: extension of the knee • Insertion: • Quadriceps tendon inserts on the superior border of the patella • Continues as the patellar ligament, which inserts on the tibial tuberosity Quadriceps femoris Knee Joint • Full extension of knee joint • Maximum congruency of the tibia and femur • Most stable • “Locking” of the bones into their best fit • Reduces the amount of muscular activity needed to little or nothing • No rotation occurs • Prevented by: • ACL • Medial collateral ligament (MCL) • Lateral collateral ligament (LCL) Knee Joint Range Of Movement (ROM) • Medial and lateral rotation • Can occur only when knee is flexed • When knee joint is flexed 45o • 40o medial rotation • 40o lateral rotation • There is less rotation at other degrees of knee flexion • Medial rotation: • Medial hamstrings • Popliteus • Lateral rotation: • Lateral hamstrings Knee Joint ROM • Flexion • About 140o • When the hip is flexed to 150o • Knee can be flexed • Hamstrings are stretched and have a greater range of contraction • When the hip is extended • Knee can be flexed to 130o • Hamstring muscles are shortened and their range of contraction at the knee is also shortened • Extension • Very limited, 5-10o • Hyperextension • Poor line of pull of the quadriceps 150o 130o Knee Joint ROM • Posterior cruciate ligament (PCL) • Tightest in full flexion • Stabilizes the knee joint in full flexion • In full extension • ACL, MCL, LCL are at their tightest Conjunct Medial & Lateral Rotation of the Knee • The articular surfaces of the knee do not fit together well Lateral condyle Shorter radius of curvature • Differences in the curvatures of the femoral condyles • Medial condyle is longer, greater radius of curvature • Lateral condyle has a shorter radius of curvature • Comes into full congruence with the tibia before the medial condyle • Also, more concave meniscotibial surface laterally Medial meniscus Oval Lateral meniscus C-shaped Conjunct Medial & Lateral Rotation of the Knee Medial facet • The lateral tibiofemoral “joint” • Begins to reach full congruence 30o before full extension • If there was no conjunct rotation Lateral facet Knee position: Flexed • Full extension of knee would be 30o from vertical • Instead, there is an involuntary medial rotation of the femur on the tibia 30o • Allows for the final of extension • While weight-bearing (WB) Semiflexed • Femur rotates medially on the tibia • If NWB • Tibia rotates laterally on the femur • Locks the knee in to full extension Fully extended Superior view of the tibia while NWB Conjunct Medial & Lateral Rotation of the Knee • “Unlocking” mechanism • Begin flexion from a fully extended position • NWB: Medial rotation of the tibia must occur • WB: Lateral rotation of the femur must occur • Popliteus • Mainly responsible for unlocking the knee joint • NWB: insertion pulled toward origin, medially rotating the tibia Knee joint In full extension Flexion of the knee joint WB: Unlocking of the Knee Joint Origin-insertion inversion: • Origin of popliteus: • Lateral femoral epicondyle • Lateral meniscus • Insertion of popliteus: • • Posterior tibia, medially The femur is pulled laterally • Lateral rotation of the femur • The lateral meniscus is pulled posteriorly and inferiorly • Posterior horn pulled opposite direction by meniscofemoral ligament(s) • Maintain congruence laterally so that medial joint can unlock