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Bones of the Knee Knee Joint • Largest and most complex joint in the body • Two sets of articular surfaces in one joint capsule: Patellar surface of femur • Patellofemoral articulation • Saddle synovial joint • Tibiofemoral articulation • Bicondylar synovial joint • Between the condyles of the...

Bones of the Knee Knee Joint • Largest and most complex joint in the body • Two sets of articular surfaces in one joint capsule: Patellar surface of femur • Patellofemoral articulation • Saddle synovial joint • Tibiofemoral articulation • Bicondylar synovial joint • Between the condyles of the femur and the condyles of the tibia Patella Fibula Tibia Distal Femur • More massive than the proximal end. Consists of: • Media and lateral condyles • Two smooth, rounded boney areas covered with articular cartilage • Inverted “U” shape • Intercondylar fossa • Non-articular area between condyles • Medial and lateral epicondyles • Non-articular areas proximal to condyles Posterior Distal Femur • The linea aspera diverges into: • Medial supracondylar line (ridge) • Flattened area 1/3 way down • Where femoral artery travels from the thigh to the popliteal fossa • Adductor tubercle is located distally on the line • Insertion of portion of adductor magnus muscle • Lateral supracondylar line (ridge) • More distinct • Popliteal surface • Located between the two lines • Popliteal = back of the knee Intercondylar Fossa (Notch) • Located between the condyles posteriorly • Non-articular area of bone for ligamentous attachment Intercondylar line • Anterior cruciate ligament (ACL) • Posterior cruciate ligament (PCL) • Numerous vascular foramina • Also numerous on the popliteal surface • Boundaries: • Posteriorly – intercondylar line • Anteriorly - patellar surface of femur • Medially/laterally - condyles Line of fibrous capsule attachment Line of attachment of synovial membrane Epicondyles of the Femur • Roughened outer areas of the distal femur • Located proximal to the articular surfaces • Both are palpable • Medial is more prominent • “Knobby knees” • Site of attachment of ligaments of the knee • Medial and lateral collateral ligaments Epicondyles of the Femur • Medial epicondyle • Just inferior to the adductor tubercle • Attachment site of medial (tibial) collateral ligament of the knee (MCL) • Lateral epicondyle • Attachment of the lateral collateral ligament (LCL) • Popliteal groove Medial view Lateral view • Located between the epicondyle and articular surface of the condyle • Origin of the popliteus muscle Medial & Lateral Condyles of Femur • Large knob-like masses of bone • Project further posteriorly than anteriorly • Form a wide base for transfer of body weight to the tibia • Covered with articular cartilage anteriorly, inferiorly and posteriorly 3 Articular Surfaces of the Condyles • Patellar (trochlear) surface Patellar surface Medial tibial surface • Where the medial and lateral condyles meet anteriorly • Articulates with the patella • Lateral aspect of the surface extends more proximally and also more anteriorly • Helps to prevent dislocation of patella • Medial and lateral tibial surfaces • Located inferiorly and posteriorly • Articulate with the tibia Lateral tibial surface Patellar (Trochlear) Surface of the Femur Knee flexed: Lateral sulcus meniscuss Groove of patellar surface • Concave from side to side and convex from proximal to distal Medial sulcus meniscus • Helps form the patellofemoral articulation • Saddle synovial joint • Grooves separate the patellar surface from the tibial surfaces Lateral meniscus • Edge of menisci sit here when knee is in full extension Medial meniscus • Lateral sulcus meniscus • Medial sulcus meniscus Tibial Surfaces of the Condyles • Convex from side to side • Convex from anterior to posterior • Medial articular surface • Longer, narrower and more curved • Articulates with medial condyle of tibia • Lateral articular surface • Wider, shorter and straighter • Articulates with lateral condyle of the tibia Posterior view Inferior view Patella (kneecap) Patellar (trochlear) surface of femur • Anterior to the knee joint • Helps protect it • Largest sesamoid bone in the body Patellar ligament Patella (posterior surface) Right Knee: Quad. tendon cut, reflected inferiorly • Sesamoid bone = bone that develops within a tendon or capsule • Lies within the quadriceps femoris tendon • Patellar ligament • Continuation of the quadriceps tendon that inserts on the tibia Quadriceps femoris tendon Patella • Triangular in shape • Apex is distal, base is proximal • Anterior surface • Convex and rough • Palpable thru the skin • Longitudinal striae (parallel lines) • Attachment of quadriceps tendon • Many vascular foramina • Nutrient arteries reach the patella thru the quadriceps tendon • Subcutaneous prepatellar bursa • Between anterior surface and skin Patella • Posterior surface • Articular and smooth • Proximal 4/5s • Lateral facet • Larger and deeper than medial facet • Medial facet • Vertical ridge • Located between the facets • Articulates with the trochlear (patellar) surface of femur • Apex is rough with foramina • Distal 1/5 • Attachment of patellar ligament Patella • Superior border • Thicker than the medial and lateral borders • Rounded and rough • Attachment site for part of the quadriceps femoris tendon • Ossification • Occurs within the quadriceps femoris tendon • Several centers of ossification appear between 3-6 years of age • Fuse together quite rapidly Patellofemoral Articulation Vertical ridge of patella • Saddle synovial joint • Both articular surfaces are concave in one direction and convex in perpendicular direction • The patella glides in the groove of the femur • As the knee extends, the patella moves more superiorly • The patella always remains the same distance from the tibial tuberosity Joint space Groove on patellar surface of femur PATELLOFEMORAL MOVEMENT EXTENDED KNEE: the patella lies against the superior part of the femoral articular surface. FLEXED KNEE: the patella has moved to a more inferior location on the femoral articular surface. Q-Angle 1 • Angle between 2 • Line 1 is from ASIS to the center of the patella • Long axis of femur • Line 2 is from the center of the patella to the tibial tuberosity • Long axis of tibia • Normal Q-angle is 10o – 20o • Average is 14o in males, 17o in females • Females have wider pelvises Q-Angle • Represents the line of the pull of the Quadriceps • Clinical measurement • Measured when patient is standing or lying down Abnormal Increase in Q-Angle • Increases the risk of patellofemoral syndrome • Pain deep to the patella, often due to excessive running, especially downhill • “runner’s knee” • Caused by abnormal tracking of the patella • As the quadriceps contract, patella is pulled laterally due to high Q-angle Patellar Dislocation • If it does occur, the patella nearly always dislocates laterally • More common in women • Due to higher Q-angles • “Q” – pull of the quadriceps Tibia and Fibula Bones of the leg: • Tibia • Larger, medial bone • Weight bearing • 2nd strongest and longest bone in the body • Part of the knee joint • Fibula • Lateral, smaller bone • Non weight bearing • Not part of the knee joint Right leg: Anterior Posterior 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 AP X-ray of Knee • Medial(1) and lateral(2) condyles of femur • Intercondylar fossa of femur(3) 3 9 6 2 9 1 4 5 9 7 8 • Intercondylar eminence of tibia, medial(4) and lateral(5) tubercles • Medial(6) and lateral(7) condyles of the tibia • Head of fibula(8) • Knee joint space(9) is radiolucent • Articular cartilage and menisci AP X-ray of Knee 2 1 4 3 • Patella(1) • Adductor tubercle(2) • Medial(3) and lateral(4) epicondyles of the femur • Epiphyseal line of the tibia(5) 5 Articular cartilage is worn down on the medial condyles of tibia and femur, resulting in joint space narrowing. • Radiopaque transverse line • Fused growth plate Lateral X-ray of Knee • Patella(1) • Condyles of femur(2) 8 • Overlap of both medial and lateral • Patellar (trochlear) surface of femur(3) • Patellar ligament(4) 1 2 3 4 5 6 • Denser than the fatty tissue deep to it 9 7 • • • • Tibial tuberosity(5) Shaft of tibia(6) Shaft of fibula(7) Shaft of femur(8) Lateral X-ray of Knee • Fabella (9) 9 • Sesamoid bone imbedded in the lateral head of the gastrocnemius muscle • Often articulates with the lateral femoral condyle • Occurs in 10-30% of the general population • 25-85% of Asian population • Usually bilateral