Knee Joint
Dr. Heba Kalbouneh Associate Professor of Anatomy and Histology Knee joint Articulating surfaces: Knee joint is the largest synovial joint in the body. Consists of two joints: Articulation between the femur and tibia
(weight- bearing)
Articulation between the patella and patellar surface of femur
Quadriceps tendon
Allows the pull of quadriceps femoris to be directed anteriorly over the knee to the Patellar tibia without tendon ligament wear Type:
Tibiofemoral joint
Modified synovial hinge (bicondylar) Allows flexion and extension with some degree of medial and lateral rotation
Patellofemoral joint
Plane gliding joint Capsule: 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 tendons 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 Ligaments:
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 Cruciate Ligament 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 fibula.
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 popliteus muscle intervenes between the ligament and the lateral meniscus
An opening in the capsule permits the tendon of the popliteus to emerge
The popliteus tendon passes between the lateral meniscus 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 intercondylar area of the tibia and passes upward, backward, and laterally, to be attached to the posterior part of the lateral wall of intercondylar fossa
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 condyles 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 bones 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 medial meniscus is attached to the capsule of the knee joint and the medial collateral ligament, it is relatively immobile Note The lateral condyle of femur is a bit longer than the medial
Helps in preventing the lateral dislocation of patella
Synovial Membrane Articularis genu The synovial membrane 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 subcutaneous tissue 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 bone. 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 gastrocnemius muscle; and beneath the medial head of origin of the gastrocnemius muscle, beneath thhe iliotibial tract The popliteal bursa is found between the tendon of popliteus and the lateral condyle of tibia 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 lateral condyle of femur by a rounded tendon Insertion: posterior surface of tibia above soleal line Unlocking means Lateral Nerve supply: Tibial nerve rotation of the femur Action: flexes leg 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 foot 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 thigh 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 nerves
Blood supply of the knee joint
Femoral, popliteal, lateral circumflex femoral arteries 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 Unhappy triad
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 Patellar tendon rupture: Sagittal radiograph Quadriceps tendon
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)