KNEE ARTHOLOGY Flashcards
Classification of the knee
Type: bicondylar hinge synovial complex and compound bi axial joint
Articulating bones: distal end of Femur, posterior surface of patella and proximal end of tibia
Articulating surfaces - Femur
Medial and lateral femoral condyle convex
Medial condyle narrower and juts out more
Intercondylar notch separates the middle and lateral condyles on the femur
Patella surface anteriorly
Articulating surfaces – Patella
Sesamoid bone
Oval articular surface divided into medial and lateral facets by vertical ridge
Articulating surfaces – tibia
All articular surfaces are covered in hyaline cartilage
Concave articular surface separated by the intercondylar eminence
Raised eminence sits in the intercondylar notch of femur
medial articulating surface is larger and concavoconex A-P than the rounded lateral surface.
Articulating areas - Uneven
Nonarticulating areas anteriorly and posteriorly to the eminence to provide attachments for both meniscus ACL and PCL
Anterior cruciate ligament
ACL
Intra-articular structure as it’s inside the knee joint
Runs from the anterolateral aspect of the anterior tibial spine passes beneath the transverse ligament to the posterior aspect of the medial surface of the lateral femoral condyle posterior laterally and proximately
Function: limits movement
Anteromedial fibres limit flexion
Posterolateral fibres limit extension
Limit 86% of anterior draw or shear of the tibia on the femur (too forward or back)
Posterior cruciate ligament
Intra– articular structure
PCL runs from a depression in the posterior intercondylar area of the tibia passes the ACL medially to the anterior aspect of the lateral surface of the medial femoral condyle anterior midline and proximately
Twice as strong is the ACL
Function: limits movement
Anteromedial fibres limit flexion
Posterolateral fibres limit extension
Limit 94% posterior draw or shear of the tibia on Femur
Meniscus (cartilage) medial
Crescent shaped fibrocartilaginous incomplete discs thicker latterly than medially
Periphery of both medial and lateral menisci attach to the joint capsule
Medial meniscus is firmly anchored to: MCL latterly transverse ligament anteriorly oblique popliteal posteriorly both anterior and posterior horns are attached to the intercondylar eminence of the tibia
Lateral meniscus also attach to transverse ligament anteriorly contributes a slip to the PCL forming the anterior posteriorly meniscofemoral ligament’s and the tendon of popliteas posteriorlly
Both anterior and posterior horns are also attached to the intercondylar eminence of the tibia
Meniscus function
Shock absorber
Increase congruence between the articular surfaces of femur and tibia
Transmission of weight-bearing activity
Lubrication keep synovial fluid pools
Locking mechanisms in extension
Joint capsule
Thick incomplete ligamentous sheath
Anteriorly:
>deficient at the femur blends with quad tendons
>more complete at the tibia only deficient at the tibial tuberosity
Posteriorly:
>fibres pass vertically from the femur to the tibia
>here they are strengthened by the oblique popliteal ligament
Medially&Laterally:
>fibres pass from the femoral to tibial condyles and blend with opl,Al,MCL,LCL
Laterally strengthened by arcuate ligament from head of fibula
Anterior attachment of joint capsule
Anterior attachment:
Anteriorly the capsular attachment to the femur is deficient blending with the quadriceps tendon
Tibial attachment— more complete only deficient at the tibial tuberosity
Posterior attachments of joint capsule
Thick incomplete ligamentous sheath
Posteriorly, the capsule fibres pass vertically from femur to tibia
Here, they are strengthened by the oblique popliteal ligament
Medially & laterally, the capsular fibres attach from the femoral to tibial condyles, where they blend with the OPL, arcuate popliteal ligament, MCL and LCL posteriorly, and with the tendinous expansion of the quadriceps femoris muscle anteriorly
The lower lateral capsule is strengthened by the APL from the fibular head
Synovial membrane
Lines joint capsule attaching to the articular margins of the femur tibia and patella
Largest in body and complex
Irregular shape with different regions folds recesses and reflections enjoying free communication with each other
Membrane is pushed backwards into the joint space by the infrapatellar fat pad and around the cruciate ligament
Synovial membrane - bursa
***Although cruciate ligaments are intracapsular there outside of the membrane = extrasynovial
Posteriorly there are recesses behind each femoral condyle where the membrane merges with two heads of the Gastrocnemius and their associated bursae and the tendon of popliteus
Bursae
A sack of fluid naturally occurring
Main role is to improve the efficiency how a joint moves or a muscle/tendon acts around a joint
4 main bursae around the knee
1) Suprapatellar bursa
Extends 6 cm above patella between femur and quadriceps femoris
2) Prepatellar bursa (Subcutaneous)
Between patella and the skin
3)Superficial infrapatellar bursa
Between patella ligament and the skin
4)Deep infrapatellar bursa
Between the upper tibia and ligamentum patella
Medial collateral ligament (MCL)
Tibial
Medial collateral ligament (MCL)
Strong flat long (8 cm)
Origin:extends from the medial epicondyle of femur inferiorly and slightly anteriorly
Insertion: to medial tibial condyle and shaft
Superficial fibres run below the tibial tuberosity
Deep fibres are shorter and spread to attach to the medial meniscus and capsule
Provide medial lateral stability and limits valgus(medial lateral) movement of the knee also contribute to the locking mechanism
Lateral collateral ligament (LCL)
Fibular
Cordlike shorter (5 cm) than MCL
Origin: Extends from the lateral epicondyle of the femur inferiorly and posteriorly
Insertion: to the lateral surface of the fibula head splits tendon of bicep femoris by attaching here
Provides medial lateral stability and limits varus (bowlegs) movement at the knee also contributes to the locking mechanism
4 ligaments that are extracapsular
MCL
LCL
Oblique popliteal ligament
Arcuate popliteal ligament
Oblique popliteal ligament
Expansion of the semimembranosus tendon passes superiorly and latterly to attach to the interchondral line of femur reinforces the central posterior capsule
Prevent hyperextension
Arcuate popliteal ligament
Attaches to the posterior aspect of the fibula head arching superiorly and medially to fan out as it attaches to the capsule posteriorly reinforces the lower lateral capsule
Prevent hyperextension
Mechanics of knee
Mechanics are complex and the knee that’s why it is a synovial complex bicondylar hinge joint
Concept of spin roll and slide all apply to the knee
Spin: one surface spins relative to the other about a thick central axis. Full extension of the knee slight medial rotation on the tibia so joint is locked. Unlock joint femur laterally rotates on tibia.
Role: one surface roles across the other, new parts of both Surfaces are continually coming into contact with each other
Slide: one surface slides over the other same part of one surface on new parts of other surface
Close pack position
Full extension
Open pack position
Flexion
Medial meniscus
Crescent shaped triangular in cross section
superior surface is concave inner border is thinner broader posteriorly less of a complete circle
The periphery is attached to the joint capsule and firmly anchored to the MCL
Anterior and posterior horns attach to the intercondylar eminence of the tibia
Posteriorly, it is attached to the oblique popliteal ligament and the transverse ligament anteriorly
Lateral meniscus
Crescent shaped fibrocartilaginous incomplete discs thicker latterly than medially
Periphery of both medial and lateral menisci attach to the joint capsule
Lateral meniscus also attaches to transverse ligament anteriorly contributes a slip to the PCL forming the anterior posteriorly meniscofemoral ligament’s and the tendon of popliteas posteriorly
Both anterior and posterior horns are also attached to the intercondylar eminence of the tibia
