Non Muscular Anatomy

Non Muscular Anatomy

Tibiofemoral Joint

Joint Orientation

·  Femur runs in a medial and inferior oblique direction from hip to knee

·  Medially deviated femur sits on a vertical tibia giving a slight valgus angulation (genu valgum)

·  Medial and lateral femoral condyles are convex

·  Medial femoral condyle extends further distally

·  Articular surface of medial condyle is longer than the lateral

·  Lateral femoral condyle lies in line with the shaft of the femur and sits anteriorly to the medial femoral condyle

·  Tibial plateaus are flat with the medial plateau longer in an A/P direction than the lateral plateau

·  Poor congruency between femoral condyles and tibial plateau

·  Menisci improve joint congruency

Menisci

·  Two fibro cartilaginous disks that are semi-circular in shape

·  Both are thicker peripherally than centrally

·  Outer 1/3 of menisci has good blood supply from capsule

·  Rest of menisci is avascular with poor chance of healing

·  Roles within the knee

o  Increase congruency

o  Distribute weight bearing across the knee

o  Act as shock absorbers

o  Aid lubrication reducing friction

o  Add nutrition to articular cartilage

o  Aid the locking mechanism of the knee

Medial Menisci

·  Larger than the lateral menisci

·  C - Shaped

·  Posterior aspect larger than the anterior

·  Anchored to medial capsule and MCL

·  Anterior horn fibres connect with transverse ligament

·  Entire periphery connects to joint capsule

·  Lots of ligamentous and capsular restraints limit mobility compared to lateral menisci

·  Limited mobility increases risk of injury

Lateral Menisci

·  More circular

·  More mobile than the medial meniscus

Ligamentous Anatomy

Transverse Ligament

·  Connects the anterior horns of medial and lateral menisci together

Coronary Ligaments

·  Part of joint capsule

·  Connect menisci to tibial plateau

·  Stabilise menisci to tibia but allow anterior and posterior translation

·  Often injured with traumatic twisting injuries

Meniscofemoral Ligament

·  Posterior horn of the lateral meniscus to the medial femoral condyle

·  Anterior Division

o  Passes anterior to PCL

·  Posterior Division

o  Passes posterior to PCL

Medial Collateral Ligament

·  Strong flat long ligament

·  Slightly posterior and proximal to medial epicondyle of femur to the medial condyle and shaft of tibial

·  Proximal fibres merge with adductor magnus

·  Deep portion is a shorter capsular thickening which attaches to the medial meniscus

·  Fibres of semimembranosus merge with deep posterior portion of MCL

·  Distal superficial fibres are separated by the pes anserinus tendons (sartorious, gracilis and semitendinosis) by a bursa

·  Resists valgus force to the knee and external rotation of the tibia

Lateral Collateral Ligament

·  Small cord like ligament

·  Extracapsular

·  More flexible than MCL meaning less chance of injury

·  From lateral epicondyle of the femur above and behind groove for popliteus

·  Attaches onto fibula head splitting tendon of biceps femoris

·  Resists varus stress particularly at 0 - 30° of knee flexion

·  Resisted tibial external rotation

Anterior Cruciate Ligament

·  Originate medial tibial

·  Passes posteriorly, laterally and proximally

·  Attaches posterior part of medial surface of lateral femoral condyle

·  Made up of 2 bands

o  Anteromedial

§  Taut in knee flexion

o  Posterolateral

§  Taut in knee extension

·  Resists anterior translation of tibia on femur

·  Resists hyperextension of the knee

·  Secondary restraint of varus/valgus motion

·  During weight bearing flexion, the femoral condyles roll posteriorly creating relative anterior translation of the tibia on the femur. An intact ACL becomes taut and limits further motion causing femur to being to glide anteriorly

·  Intracapsular, but extrasynovial

·  Genicular artery provides bloods vessels which form a periligamentous sheath around the ligament

·  Mechanoreceptors found in femoral attachment

Posterior Cruciate Ligament

·  Arises from the posterior intercondylar area of the tibia

·  Runs anteriorly, medially and proximally

·  Passes medial to ACL

·  Attaches to the lateral surface of the medial condyle of the femur

·  Twice as strong as the ACL

·  Made up of 2 bands

o  Anterolateral

o  Posteromedial

§  Merges with posterior horn of lateral meniscus and meniscofemoral ligament

·  Resists posterior translation of tibia on femur

·  Resists external rotation of tibia on femur

·  Secondary restraint of varus/valgus motion

·  Intracapsular, but extrasynovial

·  Genicular artery provides bloods vessels which for a periligamentous sheath around the ligament

·  Mechanoreceptors found in femoral attachment

Oblique Popliteal Ligament

·  Thickening of posterior capsule

·  Expansion of the semimembranosus tendon and passes superiorly and laterally to femoral intercondylar line

Arcuate Popliteal Ligament

·  Inferior lateral aspect of posterior capsule strengthened by arcuate popliteal ligament

·  From the fibula head to posterior capsule

·  Medial fibres attach onto posterior intercondylar area of tibia

·  Lateral fibres attach onto lateral femoral condyle

Joint Capsule

·  Thick ligamentous sheath composed mainly of muscle tendons and their expansions

·  Cylindrical sleeve with thickenings in various locations forming ligaments

·  Deficient anteriorly due to the patella

·  Posteriorly the capsule runs from femoral condyle and intercondylar line to posterior border of upper tibia

·  Capsular attachment anteriorly on femur is deficient as it blends with the fused tendons of the quadriceps

·  Capsular more prominent anteriorly on tibia

Synovial Membrane

·  The synovial cavity in the knee is largest in the body

·  Membrane lines the joint capsule

·  Vertical fold of synovial membrane covers cruciate ligaments anteriorly

·  No synovial membrane in cruciate triangle, making cruciate ligaments extra synovial

·  Swelling on MRI in cruciate triangle is due to cruciate tear

Bursae

·  Fluid filled sacs preventing friction

Suprapatellar Bursa

·  Between the lower part of femur and deep surface of quadriceps

Prepatellar Bursa

·  Between patella and skin

·  Can result in ‘housemaids knee’

Deep Infrapatellar Bursa

·  Between patella tendon and tibia

Superficial Infrapatellar Bursa

·  Between patella tendon and skin

Anserine Bursa

·  Between MCL and the tendons of sartorious, gracilis and semitendinosus

Medial Gastrocnemius Bursa

·  Between the medial head of gastrocnemius and the joint capsule

·  Knee joint effusion can progress into synovial effusion, causing bursitis, or Bakers Cyst

Lateral Gastrocnemius Bursa

·  Between the lateral head of the gastrocnemius and the joint capsule

Fibular Bursa

·  Between LCL and Bicep Femoris tendon

Fibulopopliteal Bursa

·  Between LCL and tendon of popliteus

Subpopliteal Bursa

·  Between popliteal tendon and lateral condyle of the femur

Semimembranosus Bursa

·  Between MCL and tendon and semimembranosus

·  Knee joint effusion can progress into synovial effusion, causing bursitis, or Bakers Cyst

Hoffa’s Infrapatella Fat Pad

·  Sits between the joint capsule and synovial membrane

·  Between infrapatella tendon/ligament and knee joint

·  Can become impinged or damaged in trauma

Arthrokinematics

Rules of concavity and convexity

·  Movements at joint surfaces follow the rules of concavity and convexity

·  Each joint involves two bony surfaces one that is convex and one that is concave

·  When the concave surface is fixed and the convex surface moves on it, the convex surface rolls and glide in opposite directions

·  When the convex surface is fixed and the concave surface moves on it the concave surface rolls and glides in the same direction

Tibiofemoral Joint
Capsular Pattern / Flexion more than Extension
Resting Position / 20° Flexion
Close Packed Position / Full Extension and Tibial External Rotation
End Feel / · Flexion- SOFT – tissue approximation
· Extension- HARD
Movements / Knee Extension
·  Open Chain
o  Tibia Glides Anteriorly and Rolls Anteriorly
o  Tibia external rotation from 20° Flexion to Full Extension
·  Closed Chain
o  Femur Glides Posteriorly and Rolls Anteriorly
o  Femur Internally rotates on stable Tibia from 20° Flexion to Full Extension
Knee Flexion
·  Open Chain
o  Tibia Glides Posteriorly and Rolls Posteriorly
o  Tibia internal rotation from Full Extension to 20° Flexion
·  Closed Chain
o  Femur Glides Anteriorly and Rolls Posteriorly
o  Femur Externally rotates on stable Tibia from Full Extension to 20° Flexion
Internal Rotation – 0 - 15° of knee flexion- Maximal passive rotation can occur at 45° due to decreased tension in soft tissue
External Rotation – 0 – 20° of knee flexion- Maximal passive rotation can occur at 45° due to decreased tension in soft tissue
Adduction
Abduction

“Screw Home” Mechanism

·  Rotation between full extension and 20° Flexion occurs automatically due to the tibial medial condyle being longer than the lateral

Knee Extension

·  Tibia glides anteriorly on femur

·  During the last 20° of extension the anterior tibial glide continues on the medial condyle

·  Prolonged anterior glide on medial side causes tibial external rotation

Knee Flexion

·  Posterior glide of tibia beings first on the longer medial condyle

·  This causes relative internal rotation of tibia up to 20° of flexion

Patellofemoral Joint

Joint Orientation

·  Anterior surface of the femoral condyles

·  Posterior surface of the patella

·  Posterior surface of the patella is divided into medial and lateral facets

·  4-5 mm of articular hyaline cartilage on patella

Ligamentous Anatomy

Ligamentum Patellae(Patellar Tendon)

·  Continuation of quadriceps tendon

·  Attaches into the tibial tuberosity

Meniscopatellar Fibres

·  Fibrous bands running from patella to lateral aspect of medial and lateral menisci

Medial Patella Retinaculum

·  Aponeurotic tendon of Vastus Medialis expands over capsule and attaches onto medial patella facet and medial tibial condyle

·  Composed of patellofemoral and patellotibial ligaments

Lateral Patella Retinaculum

·  Aponeurotic tendon of Vastus Lateralis expands over capsule and attaches onto lateral patella facet and lateral tibial condyle

·  Composed of patellofemoral and patellotibial ligaments and iliotibial tract

Arthrokinematics

Patellofemoral Joint
Capsular Pattern / Flexion limited more than Extension
Resting Position / Full Knee Extension
Close Packed Position / Full Knee Flexion
End Feel / · NA
Movements / · Terminal Extension- Patella Does not articulate with trochlea of femur
· 10° of knee flexion, inferior patella articulates with the proximal articular surface of the femur
· Through flexion patella glides inferiorly, femur rolls posteriorly
· Articulating surface of patella moves proximately with increased flexion
· Articulating surface of femur moves posteriorly with increased flexion
· The contact surface of the patellofemoral joint increases with flexion
· Medial facet of patella only becomes in contact at end range flexion

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