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Knee Joint

Knee Joint

Dr. Heba Kalbouneh Associate Professor of and Histology Knee joint Articulating surfaces: Knee joint is the largest in the body. Consists of two : Articulation between the and

(weight- bearing)

Articulation between the and patellar surface of femur

Quadriceps

Allows the pull of quadriceps femoris to be directed anteriorly over the knee to the Patellar tibia without tendon wear Type:

Tibiofemoral joint

Modified synovial hinge (bicondylar) Allows flexion and extension with some degree of medial and lateral rotation

Patellofemoral joint

Plane gliding : The capsule is attached to the margins of the articular surfaces and surrounds the sides and posterior aspect of the joint.

On the front of the joint, the capsule is absent. The capsule is completed anteriorly by patella, ligamentum patellae, medial and lateral patellar retinacula

Posterior view of the knee On each side of the patella, the capsule is completed anteriorly by expansions from the of vastus lateralis and medialis forming Medial and Lateral patellar retinacula

The ligamentum patellae is attached above to the lower border of the patella and below to the tuberosity of the tibia.

Lateral patellar Medial patellar retinaculum retinaculum

Patellar ligament :

The ligaments may be divided into those that lie outside the capsule (extracapsular) and those that lie within the capsule (intracapsular)

Extracapsular ligaments: Ligamentum patellae Lateral collateral ligament Medial collateral ligament Oblique popliteal ligament

Intracapsular Ligaments (within the joint cavity): Anterior Posterior Cruciate Ligament The lateral collateral ligament is cordlike and is attached above to the lateral femoral epicondyle and below to the head of the .

The medial collateral ligament is a flat band and is attached above to the medial femoral epicondyle and below to the upper medial surface of tibia. Why???

The tendon of the intervenes between the ligament and the lateral

An opening in the capsule permits the tendon of the popliteus to emerge

The popliteus tendon passes between the and What does this mean?? the capsule

Posterior view of the knee The oblique popliteal ligament is a tendinous expansion derived from the semimembranosus

muscle. It strengthens the

posterior aspect of the capsule Semimembranous Semimembranous Cruciate: latin for shaped like a cross

Anterior Posterior Cruciate Cruciate Ligament Ligament

The cruciate ligaments are named anterior and posterior, according to their tibial attachments

Are the main bond between the femur and the tibia throughout the joint's range of movement

Anterior view of the knee The anterior cruciate ligament is attached to the anterior of the tibia and passes upward, backward, and laterally, to be attached to the posterior part of the lateral wall of intercondylar

The anterior cruciate ligament restricts anterior displacement of the tibia relative to the femur The posterior cruciate ligament is attached to the posterior intercondylar area of the tibia and passes upward, forward, and medially to be attached to the anterior part of the medial wall of intercondylar fossa

The anterior cruciate ligament restricts posterior displacement of the tibia relative to the femur

The tests for the integrity of the cruciate ligaments are the anterior and posterior drawer signs Tearing of the anterior cruciate ligament Tearing of the posterior cruciate ligament allows the tibia to be easily pulled allows the tibia to be easily pulled forward posteriorly (anterior drawer sign) (posterior drawer sign)

Test anterior cruciate ligament Test posterior cruciate ligament

Ruptured ACL Ruptured PCL Menisci

 Are medial and lateral C- shaped fibrocartilages  The upper surfaces are in contact with femoral The lower surfaces are in contact with tibial condyles.  Their function is to deepen the articular surfaces of the tibial condyles to receive the convex femoral condyles; they also serve as cushions between the two Each meniscus is attached to the upper surface of the tibia by anterior and posterior horns Superior view of the proximal end of Tibia Medial collateral ligament

Medial meniscus

The is attached to the capsule of the knee joint and the medial collateral ligament, it is relatively immobile Note The lateral of femur is a bit longer than the medial

Helps in preventing the lateral dislocation of patella

Synovial Membrane Articularis genu The lines the capsule

The synovial membrane of the knee joint forms pouches (bursae)

To provide low-friction surfaces for the movement of tendons associated with the joint Some bursae communicate with the joint cavity and some do not normally communicate

For example On the front and above the joint, it forms a pouch, which extends up beneath the quadriceps femoris for three fingerbreadths above the patella, forming the suprapatellar bursa. This is held in position by the attachment of the articularis genu muscle Note: Note: Suprapatellar bursa communicates with the joint cavity Suprapatellar Consequently, abrasions or bursa penetrating wounds (e.g stab wounds) superior to the patella may result in suprapatellar bursitis caused by bacteria entering the bursa from the torn skin. The infection may spread to the knee joint The prepatellar bursa lies in the between the skin and the patella Prepatellar bursa

Prepatellar bursitis (housemaid’s knee)

Is usually a friction bursitis caused by friction between the skin and patella The superficial infrapatellar Subcutaneous bursa lies in the subcutaneous infrapatellar tissue between the skin and the bursa ligamentum patellae

Subcutaneous infrapatellar bursitis results from excessive friction between the skin and tibial tuberosity Deep The deep infrapatellar bursa infrapatellar lies between the ligamentum bursa patellae and the tibia

Infrapatellar fat pad Bursae are found wherever skin, muscle, or tendon rubs against . Four are situated in front of the joint and the rest are found behind the joint

Subtendinous Anserinus bursa of biceps bursa femoris The other bursae are found related to the tendon of insertion of the biceps femoris; related to the tendons of the sartorius, gracilis, and semitendinosus muscles as they pass to their insertion on the tibia; beneath the lateral head of origin of the ; and beneath the medial head of origin of the gastrocnemius muscle, beneath thhe The popliteal bursa is found between the tendon of popliteus and the and communicates with the joint cavity. The cruciate ligaments lie behind the synovial cavity and are not bathed in synovial fluid. Locking mechanism When standing the knee joint is locked into position, thereby reducing the amount of muscle work needed to maintain the standing position

Locking mechanism has 3 components:

1- The change in the shape and size of the femoral articular surfaces 2- The medial rotation of the femur on the tibia during extension

Medial rotation and full extension tightens all the associated ligaments

3- The body’s center of gravity is positioned along vertical line that passes anterior to the knee joint

Keeps the knee extended when standing Note The joint surfaces become larger and more stable in extension

The extended knee is said to be in the locked position Before flexion of the knee can occur, it is essential that the major ligaments Be untwisted/ slackened to permit movements between the joint surfaces

This unlocking or untwisting process is accomplished by the popliteus muscle

Which laterally rotates the femur on tibia

The knee joint can not be flexed unless it is unlocked by the popletius Popliteus Origin: lateral surface of by a rounded tendon Insertion: posterior surface of tibia above Unlocking means Lateral supply: rotation of the femur Action: flexes at knee Or Medial rotation of the joint, unlocks the extended tibia knee at the initiation of flexion by lateral rotation Locking means………….. of femur on tibia (when rotation of the femur Or …………rotation of the the is on the ground) tibia and slackens ligaments of knee joint Medial rotates the tibia on the femur Note The popliteus arises within the knee joint

Its tendon separates the lateral meniscus from the lateral collateral ligament and the capsule

It emerges through the lower part of the posterior surface of the capsule to pass to its insertion Movements of the knee joint Flexion Biceps femoris, Semitendinosus, and Semimembranosus muscles, assisted by Gracilis and Sartorius muscles Flexion is limited by the contact of the back of the leg with the Extension Quadriceps femoris Extension is limited by the tension of all the major ligaments of the joint. Medial Rotation Sartorius, Gracilis, and Semitendinosus Lateral Rotation Biceps femoris

The stability of the knee joint depends on the tone of the strong muscles acting on the joint and the strength of the ligaments.

Of these factors, the tone of the muscles is the most important, and it is the job of the physiotherapist to build up the strength of these muscles, especially the quadriceps femoris, after injury to the knee joint. Nerve supply of the knee joint

Femoral, obturator, common fibular and tibial

Blood supply of the knee joint

Femoral, popliteal, lateral circumflex femoral The medial collateral ligament is firmly attached to the capsule and medial meniscus

Tibial collateral ligament extends from medial epicondyle of femur to medial aspect of tibia

The tibial collateral ligament prevents lateral displacement (abduction) of tibia under femur The 3 most commonly injured structures at the knee are: Tibial collateral ligament Medial meniscus ACL

The terrible or

Usually results from a blow to the lateral aspect of the knee with the foot on the ground

Knee joint and menisci from above ACL and PCL attachment points Prepatellar bursitis (housemaid’s knee) Lateral collateral ligament: isolated from knee joint

Note: it is cord-like Medial collateral ligament: isolated from knee joint

Note: it is flat rupture: Sagittal radiograph

Femur Suprapatellar bursa

Lateral meniscus

Patella Tibia

Patellar ligament Fibula

MRI of the Knee (Sagittal View) Femur PCL

Lateral meniscus Medial meniscus

Tibia ACL

MRI of the Knee (Coronal View)