STRUCTURE OF KNEE JOINTSTRUCTURE OF KNEE JOINT

By: Anita Sarin M.N.(Previous) RAKCON

By: Anita Sarin M.N.(Previous) RAKCON

KNEE ANATOMY

• Bones – femur– fibula– tibia – patella

• Articulations– tibiofemoral– patellofemoral

ANATOMY cont.

• Menisci– Medial meniscus– Lateral meniscus– Blood supply (3 vascular zones)– Versus hyaline cartilage

• Ligaments– Medial collateral - MCL (deep & superficial)– Lateral collateral - LCL– Cruciates - ACL & PCL

ANATOMY cont.

• Joint Capsule• Synovial Capsule• Knee musculature– quadriceps group– hamstrings group– iliotibial band– gastroc, gracilis, sartorius, popliteus, plantaris

• Patellar tendon

ANATOMY cont.

• Additional Knee Structures– Bursa– Popliteal fossa– Fat pads / plica– Nerves– Blood vessels

Knee joint

– largest joint in body

– very complex

– primarily a hinge joint

© 2007 McGraw-Hill Higher Education. All rights reserved. 10-11

Bones

• Enlarged femoral condyles articulate on enlarged tibial condyles

• Medial & lateral tibial condyles (medial & lateral tibial plateaus) - receptacles for femoral condyles

• Tibia – medial– bears most of weight

Bones

• Fibula - lateral– serves as

the attachment for knee joint structures

– does not articulate with femur or patella

– not part of knee joint

KNEE JOINT

• The knee joint joins the thigh with the leg and consists of two articulations; one between the femur and tibia and one between the femur and patella.

• Since the knee supports nearly the whole weight of the body, it is the most vulnerable both to acute injury and osteoarthritis

Bones• Patella– sesamoid

(floating) bone– imbedded in

quadriceps & patellar tendon

– serves similar to a pulley in improving angle of pull, resulting in greater mechanical advantage in knee extension

• The knee joint (tibio femoral joint) is the largest and most complex joint of the body actually consisting of three joints within a single synovial cavity.

• Laterally is a tibiofemoral joint, between the lateral condyle of the femur, lateral meniscus, and lateral condyle of the tibia.

• Medially is a second tibiofemoral joint, between the medial condyle of the femur, medial meniscus, and medial condyle of the tibia.

• An intermediate patellofemoral joint, between the patella and the patellar surface of the femur.

KNEE JOINT

• The knee joint (tibio femoral joint) is the largest and most complex joint of the body actually consisting of three joints within a single synovial cavity.

• Laterally is a tibiofemoral joint, between the lateral condyle of the femur, lateral meniscus, and lateral condyle of the tibia.

• Medially is a second tibiofemoral joint, between the medial condyle of the femur, medial meniscus, and medial condyle of the tibia.

• An intermediate patellofemoral joint, between the patella and the patellar surface of the femur

ANATOMICAL COMPONENTS

• Articular capsule – No complete, independent capsule unites the bone of the knee joint. The ligamentous sheath surrounding the joint consists mostly of muscle tendons or their expansions

• Medial and lateral retinacula- Fused tendons of insertion of the quadriceps femoris muscle and the fascialata (deep fascia of thigh) that strengthen the anterior surface of the joint

KNEE JOINT

• Patellar ligament- Continuation of the common tendon of insertion of the quadriceps femoris muscle that extends from the patella to the tibial tuberosity

• Oblique popliteal ligament- broad flat ligament that extends from the intercondylar fossa of the femur to the head of the tibia

• Arcuate popliteal ligament- extends from the lateral condyle of the femur to the styloid process of the head of the fibula

• Tibial collateral ligament- broad flat ligament on the medial surface of the joint that extends from the medial condyle of the femur to the medial condyle of the tibia.

• Intracapsular ligaments-ligaments within the capsule that connect the tibia and femur.

• Anterior cruciate ligament (ACL)- extends posteriorly and laterally from a point anterior to the intercondylar area of the tibia to the posterior part of the medial surface of the lateral condyle of the femur

• Posterior cruciate ligament (PCL) - extends anteriorly and medially from a depression on the posterior intercondylar area of the tibia and lateral meniscus to the anterior part of the lateral surface of the medial condyle of the femur.

•  

• Articular discs (menisci) - two fibrocartilage discs between the tibial and femoral condyles help compensate for the irregular shapes of the bones and circulate synovial fluid.

• Medial meniscus-semicircular piece of fibrocartilage (C-shaped)• Lateral meniscus- nearly circular piece of fibrocartilage (approaches an

incomplete O in shape)• The medial and lateral menisci are connected to each other by the

tranverse ligament and to the margins of the head of the tibia by the coronary ligament.

•  

• The more important bursae of the knee include the following;• Prepatellar bursa- between the patella and the skin• Infrapatellar bursa- between the superior part of the tibia

and patellar ligament• Suprapatellar bursa- between inferior part of the femur and

deep surface of quadriceps femoris muscle.•

Right knee-joint. Anterior view Right knee-joint. Posterior view.

• Medial and Lateral• Lateral: circular, mobile,

attached to popliteus• Medial: ‘C’ shaped, less

mobile

• Pressure absorbers• Joint stability• Lubrication

Movements

• Flexion– bending or decreasing angle

between femur & leg, characterized by heel moving toward buttocks

• Extension– straightening or increasing

angle between femur & lower leg

Movements

• External rotation– rotary movement of leg

laterally away from midline

• Internal rotation– rotary movement of lower leg

medially toward midline

• Neither will occur unless flexed 20-30 degrees or >

• MOVEMENTS• The knee joint allows • Flexion• Extension• Slight medial rotation• Lateral rotation of leg in the flexed position.•

Anatomy-Ligaments

• ACL-anterior cruciate ligament– Runs from anterior tibia to posterior femur– Prevents anterior displacement of tibia on fixed

femur– Prevents femur from moving posterior during

weight bearing– Stabilizes tibia against excessive internal rotation

Ligaments

• PCL-posterior cruciate ligament– Runs from posterior tibia to anterior femur– Prevents posterior translation of tibia on fixed

femur– Prevents femur from moving anterior during

weight bearing

• Both ACL and PCL “cross” or wrap around each other—taut when in extension and looser when in flexion

Ligaments

• MCL-medial collateral ligament– Attaches on the medial femoral epicondyle &

anteromedial tibia– Thickened portion of joint capsule– Two parts-superficial and deep• Deep portion attaches to medial meniscus

– Stabilizes against valgus stress applied to lateral aspect of joint capsule

Ligaments

• LCL-lateral collateral ligament– Attaches to lateral femoral epicondyle and head

of fibula– Stabilizes against varus stress when force is

applied to medial aspect of joint

• Both the MCL and LCL are tightest during full extension of knee and relaxed during flexion

Ligaments

Knee Joint Capsule

• Fibrous capsule reinforced by muscles, tendons, ligaments and fascia

• No bony block against hyperextension; muscles and capsule limits hyperextension

Menisci

• Menisci – crescent shaped fibrocartilagenous discs located within the knee joint

• Medial “C” shaped; & Lateral “O” shaped• Loose ligamentous attachment to tibia and joint capsule allows

menisci to pivot/slide during knee movement• Shock absorption – reduces compressive stress• Deepens articular surface of tibia for femoral condyles; increases joint contact 3X

• Guides femoral motion

• KNEE INJURIES• The knee joint is the most vulnerable to damage because it is a mobile,

weight-bearing joint and its stability depends almost entirely on its associated ligaments and muscles.

• A swollen knee may occur immediately or hours after injury. Immediate swelling is due to escape of blood from damaged blood vessels.

• Delayed swelling is due to excessive production of synovial fluid.• A dislocated knee refers to the displacement of the tibia relative to the

femur. The most common type is dislocation anteriorly, resulting from hyperextension of the knee. A frequent consequence of dislocation is damage to the popliteal artery.