Functional anatomy of the kneeThe articular bones of the knee have a little contribution to the stability of the joint.Stability of the knee joint depends mainly on its supporting soft tissue structures.
:Medial supporting structures 3 layers Superficial layer: Crural fascia (fascia continuous anteriorly with fascia covering vastus medialis & posteriorly with fascia covering sartorius muscle). Middle layer: Superficial MCL Deep layer: Deep MCL (medial capsular ligament).
Superficial layer unite with middle layer anteriorly to form the medial patellar retinaculum. It separated from the middle layer in the middle third by fatty tissue. The middle layer unite with the deep layer posteriorly to form the posterior oblique ligament. The middle layer is separated from the deep layer at the middle third by fatty tissue & medial collateral bursa.
Superficial Medial collateral ligament Anterior vertical portion;Which is separated from the deep MCL by fat and MCL bursa. Posterior oblique portionWhich blends with the posterior medial meniscus (forming what is called posterior oblique ligament).
Deep medial collateral ligament Menisco-tibial attachment. Menisco-femoral attachment.
Medial supporting structuressuccessive coronal PD W images
Medial supporting structures Axial PD WI obtained Axial PD WI obtained above the level of at the level of joint joint space space
Posteromedial supporting structures Semimembranosis muscle & tendon. Medial head of gastrocnemius Posterior oblique ligament(obliquely oriented portion of MCL). Joint capsule
Postero-medial supporting structures Sagittal T1 WI shows: origin of medial head of gastrocnemius from medial supracondylar ridge & insertion of semimebranosis tendon in the posterior tibia.
:Lateral supporting structures3 layers:Superficial layer: iliotibial tract & its anterior expansion. Biceps tendon & its posterior expansion.Middle layer: Lateral patellar retinaculum which is complete anteriorly and represented posteriorly by 2 patellofemoral ligaments.Deep layer:Superficial lamina: LCL And terminates at the fabellofibular ligament.Deep lamina: The coronay ligament (with its meniscotibial & mensico- femoral attachment). And terminates at the arcuate ligament.
Anterolateral supporting structures Iliotibial tract. (inserted in Gerdy’s tubercle). Superior and inferior Lateral patellar retinacula. Vastus lateralis muscle. Joint capsule.
LCL: Lateral femoral Styloid process. Lateral stabilizer & epicondyle. external rotator of the tibia.Popliteal Posteromedial Popliteal sulcus in Lateral stabilizer & internalmuscle & surface of the the lateral rotator of the tibia.tendon tibia. femoral condyle (intra-articular).Popliteal Popliteal tednon Lateral meniscus. Prevent excessive forwardmeniscal displacement of the lateralligament: meniscus during extension of the knee.Popliteal Popliteal tendon. Styloid process of Acts as a pully fixing thefibular the fibula. muscle in position duringligament: contraction.Oblique Recurrent fascicle arcuate ligament. Reinforces the posteriorpopliteal of capsule.ligament: semimembranosi s tendon.Arcuate lateral limb; medial limb;ligament: blends with the curves over theV shaped capsule near the popliteal tendon &thickening of lateral head of joins the obliquethe posterior gastrocnemius. poplitealcapsule. ligament.fabellofibular fabella or lateral styloid process ofligament: femoral condyle. the fibula.
Types of injury pure hyperextension; hyperextension with varus; hyperextension with valgus; pure valgus; pure varus; flexion with valgus, external rotation; flexion with varus, internal rotation; flexion with posterior tibial translation; patellar dislocation (flexion, valgus, internal rotation of femur on tibia); and direct trauma.
Hyperextension injuryIncidence: Pure hyperextension. 2% Hyperextension with varus. 8% Hyperextension with valgus. 2%
Trauma of hyperextension injury Forces applied to hyperextended (locked) knee: Types of trauma Direct trauma Indirect trauma
Restraints of hyperextension1ry restraints of hyperextension: PCL.2ry restraints of hyperextension: ACL. Posterior supporting structures:
Effects of hyperextension injury Effects of hyperextension injuryImpaction injury Distraction injury Avulsion bone Distraction marrow contusion soft tissue injury
Impaction injuryKissing (contiguous) Bone marrowcontusions of the anterior aspect ofthe femoral condyles & anterior tibialplateau.If varus force applied duringhyperextension, the bone marrowcontusion will be located moremedially & vice versa.
Impaction injury in pure hyperextension Kissing bone marrow contusions of the anterior surfaces of the femum and tibia.
Impaction injury in hyperextension with varus Kissing bone marrow contusions of the medial femoral & tibial condyles
Impaction injury in hyperextension with valgus Kissing bone marrow contusions of the anterior extents of lateral femoral and tibial condyles.
Distraction injury Distraction bone injury Pure Hyperextension Hyperextensionhyperextension with varus with valgus
Distraction bone injury in pure hyperextension Avulsion bone marrow contusion of the posterior tibial plateau.
Distraction injury inhyperextension with varus Arcuate fracture: Avulsion fracture of the styloid process of the fibula.
Distraction injury in hyperextension with valgus Avulsion bone marrow contusion of the posteromedial tibial plateau.
Distraction soft tissue injury Pure Hyperextension Hyperextensionhyperextension with valgus with varus
Distraction soft tissue injury ((pure hyperextensionACL tear.PCL tear.Injury of the posterior supporting structures: (posterior capsule disruption or injury to gastrocnemius muscle).Injury to the popliteal vessels
Distraction soft tissue injury ((hyperextension with varus ACL injury. PCL injury. Posterior capsule disruption. Injury of the posterolateral supporting structures (posterolateral corner syndrome).
Posterolateral corner syndromeUnrecognized injuries to the posterolateral corner is an important factor in postsurgical failure after cruciate ligament reconstruction and in chronic instability and degenerative changes after knee trauma
Lateral collateral ligament tear Coronal PD WI with FS shows: complete tear of the LCL with soft tissue edema. Coronal PD WI shows: diffuse thickening of the LCL suggestive of partial tear.
Injury of the popliteal muscle & tendon Injury of the popliteal myotendineous junction. Avulsion injury of the popliteal tendon.
Injury of the biceps tendon Coronal T1 W image shows thickening, heterogeneity & retraction of the biceps tendon evidence of its complete tear.
Distraction soft tissue injury ((hyperextension with valgusPosteromedial instability: Injury of semimembranosis tendon. Injury of the medial head of gastrocnemius.
Axial PD WI with FS shows intrasubstance partial tear of the semimembranosis tendon.Sagittal T2 WI shows partial tear of the medial head of gastrocnemius and semimembranosis tendon.
Flexion with valgus & external rotationIncidence: 46%Trauma:Pivot shift injury during skiing .
Effects of Pivot shift injury Effects of Pivot shift injuryImpaction injury Distraction injury Avulsion bone Distraction marrow contusion soft tissue injury
Impaction injury Non kissing contusions of the lateral femoral condyle & posterolateral tibial plateau.
Distraction injuryAvulsion bone marrow contusions at the: posteromedial tibial plateau & medial femoral condyle(attachments of coronary ligaments).
Distraction soft tissue injuryO’ Donoghue’s triad: ACL injury. MCL injury. Tear of the posterior horn medial meniscus.
Flexion with varus and internal rotationIncidence: 1%Trauma:pivoting during deceleration with change direction.
Effects of deceleration injury Effects of deceleration injury Impaction injuryNon kissing contusions of Distraction injury& lateral femoral condyle posterior tibial plateau Avulsion fracture of Distraction Gerdy’s tubercle soft tissue injury (Segond fracture) Anterolateral instability
Impaction injury Non contiguous bone marrow contusions of the lateral femoral condyle & the posterolateral tibial plateau.
Distraction injury Coronal PD FS WI shows avulsion fracture of the Gerdy’s tubercle with subcortical oedema (Segond fracture).
Distraction soft tissue injury Anterolateral instability Midsubstance tear of the ilitibial tract rather than avulsion of the Gerdy’s tubercle.
Hyperflexion injury with posterior tibial dislocation Effects of Dash board injury Impaction injuryBone marrow contusion of Distraction injury The anterior tibia Distraction soft tissue injury Avulsion fracture of PCL The posterior tibial plateau Posterior joint capsule Gastrocnemius muscle
Impaction injury Bone marrow contusion of the anterior tibia
Distraction injury Avulsion fracture of the posterior tibial plateau
Distraction soft tissue injuryPCL tear Midsubstance tear. Avulsion of the tibial attachment. Avulsion of the femoral attchment.Injury of the posterior joint capsule.Injury of the gastrocnemius muscle.
Disruption of the posterior capsule Sagittal STIR WI showing complete avulsion of the femoral attachment of the PCL with disruption of the posterior capsule & bone marrow oedema of the anterior tibia.
Injury of the gastrocnemius muscle Grade I sprain:Interstitial oedema (giving feathery appearance on STIR & T2 images).Intramuscular hematoma.Grade II:Partial tear without retraction.Grade III:Complete tear with retraction.