2.4 Flashcards
What are the 3 joints of the knee?
femoropatellar joint
lateral femorotibial joint
medial femorotibial joint
The proximal tibiofibular joint is not a knee joint because of its movement.
Knee capsule
Synovial joint surrounded by a fibrous capsule
Some ligaments are continuous with fibrous capsule
Synovial membrane separates from the fibrous capsule in the center
2 layers:
1. fibrous: intrinsic ligaments
2. Synovial: lines fibrous layer laterally and separate medially
What type of joint is the knee?
It’s primarily a hinge joint allowing flexion and extension.
It also allows some sliding, rolling, and slight rotation.
Support for the knee joint
Surrounding muscles and tendons
Ligaments of femur and tibia
Anteriorly: quadriceps tendon/ patellar ligament
Laterally: IT band
Medially: pes anserinus
NO CONTRIBUTION FROM THE FIBULA
What is the “screw-home” mechanism?
The “screw-home” mechanism is a medial rotation of the femur on a fixed tibia that occurs at the end of knee extension to “lock” the knees. In order to initiate knee flexion from a fully extended state, the popliteus muscle laterally rotates the femur on the tibia to “unlock” the knee. Once unlocked, primary knee flexor can mediate knee flexion.
Knee extensors
quadriceps femoris
Knee flexors
hamstrings and sartorius
Knee rotators
hamstrings and sartorius
Collateral ligaments of the knee
Lateral (fibular)collateral ligament (LCL)
- cord-like, extracapsular ligament
- lateral femoral condyle –> fibular head
- not attached to lateral meniscus
Medial (tibial) collateral ligament (MCL)
- broad, capsular (intrinsic) ligament
- medial femoral epicondyle –> medial tibial condyle
- attached to medial meniscus at midpoint
- more commonly injured than LCL
Both ligaments prevent rotation and lateral flexion in the coronal plane.
Cruciate ligaments of the knee
Anterior cruciate ligament (ACL)
- limits anterior translocation (movement in abnormal direction)
- anterior, intercondylar tibial plateau –> posterior part of lateral femoral condyle
Posterior cruciate ligament (PCL)
- limits posterior translocation
- posterior, intercondylar tibial plateau –> anterior part of lateral femoral condyle
Intracapsular: within joint capsule
Extrasynovial: synovial membrane is folded around the ligament
MMT for cruciate ligaments
Anterior drawer test:
- pull tibia anteriorly with flexed knee
- tests ACL integrity
Posterior drawer test:
- push tibia posteriorly with flexed knee
- tests PCL integrity
Menisci
Medial and lateral
2 crescent shaped fibrocartilage pads within the knee joint
wedge shaped in axial section
Function: shock absorption and deepens articular surface
Medial meniscus is more prone to injury because of where it’s attached. It’s less mobile and fixed to ACL.
Unhappy triad
The simultaneous tearing of the ACL, MCL, and medial meniscus caused by a lateral blow to the knee when the foot is fixed to the ground.
Knee bursae
Acute (sudden) or chronic trauma can lead to bursitis and swelling of the knee.
Prepatellar bursa is common in people who work on their knees, like carpet and tile installers.
Label
- lateral meniscus
- LCL
- head of fibula
- medial meniscus
- MCL
- ACL
- PCL
Which ligament is torn?
A. patellar
B. MCL
C. LCL
D. ACL
E. PCL
D. ACL
Varus and valgus stress
Q angle
The measure of angle between 2 lines
1. ASIS to patella
2. tibial tuberosity through midpoint of patella
Clinically used to evaluate varus or valgus stress
Oblique arrangement of femur in the thigh places the tibial axis directly under femoral head and weight centered in the middle of the tibial plateau. With varus and valgus stress on the knee, weight is shifted over one side of the tibia, which can cause wearing of the joint cartilages and ligament articular cartilage (osteoarthritis), meniscus, MCL/LCL.
Popliteal fossa
Diamond-shaped region behind the knee
Marks the transition region between the thigh and the leg
Vascular components of the thigh pass to the flexor side of the knee
Covered by popliteal fascia
Arteries of popliteal fossa
Femoral artery becomes popliteal artery when it passes through the adductor hiatus
Genicular arteries branch to give blood supply to the knee joint.
Neurovasculature of knee and popliteal fossa
Transition and division
1. popliteal artery divides anterior and posterior tibial arteries
2. sciatic nerve divides tibial nerve and common fibular nerve
3. small saphenous vein empties into popliteal vein
The genicular arteries help to form an anastomosis of the knee joint to maintain blood flow to the distal leg if the popliteal artery becomes “kinked” which can happen during full knee flexion.
Baker’s cyst
Swelling of the synovium of the knee
Produces an enlarged synovial cyst in the popliteal fossa
Causes knee injury and arthritis
Usually minimally painful, but can impinge neurovasculature
Important to differentiate from a popliteal aneurism or DVT
Compartments of the leg
Anterior
- dorsiflex (extend) and invert/evert
- toe extension
- innervated by deep fibular n.
- supplied by anterior tibial a.
Lateral
- evert foot and ankle
- weak plantarflexion
- innervated by superficial fibular n.
- supplied by branches of fibular a.
Posterior
- primarily plantarflexion and inversion
- toe flexion
- innervated by tibial n.
- supplied by posterior tibial a.
Compartment syndromes
Pressure within a closed compartment exceeds the perfusion pressure resulting in muscle and nerve ischemia
Signs:
1. Pain
2. Palor - pale, loss of color
3. Paresis - weakness
4. Paresthesia - abnormal feeling (tingling, pins and needs)
5. Pulselessness
Treatment: fasciotomy
List muscles of posterior leg
2 muscle groups:
Deep
- tibialis posterior
- flexor digitorum longus
- flexor hallicus longus
- popliteus
Superficial
- gastrocnemius
- soleus
- plantaris
Achilles Tendon
Most powerful (strongest and thickest) tendon
- Avulsion from calcaneus or tendon rupture results in loss of plantarflexion. This interferes with the push off phase of gait, jumping, etc.
- Subcutaneous bursa - allows the skin to move over the tendon
- Retrocalcaneal bursa - allows the tendon to glide over the calcaneus
Achilles Tendon Reflex (ankle jerk reflex)
Tests S1-S2 nerve roots and tibial nerve
Tap Achilles tendon with reflex hammer just proximal to calcaneus
Plantarflexion of ankle should result
Gastrocnemius
O: condyles of the femur
I: calcaneus via Achilles tendon
A: plantarflexion, raises heel when walking
N: tibial n.
Blood supply: posterior tibial a.
Soleus
O: proximal tibia/fibula
I: calcaneus via Achilles tendon
A: plantarflexion, raises heel when walking
N: tibial n.
Blood supply: posterior tibial a.
Plantaris
O: inferior end of supracondylar line
I: calcaneus via Achilles tendon
A: plantarflexion, raises heel when walking
N: tibial n.
Blood supply: posterior tibial a.
(YELLOW)
Popliteus
Short muscle that crosses knee and is important for unlocking the knee
O: lateral condyle of femur
I: posterior tibia
A: lateral rotation for flexion
N: tibial n.
Blood supply: posterior tibial a.
Tibialis posterior
O: interosseus membrane
I: plantar surface of foot
A: plantarflexion, inversion
N: tibial n.
Blood supply: posterior tibial a.
Flexor digitorum longus
O: medial part of posterior tibia
I: distal phalanges 2-5
A: plantarflexion, flexion of digits 2-5
N: tibial n.
Blood supply: posterior tibial a.
Flexor hallicus longus
O: inferior, posterior fibula
I: distal phalanx of great toe
A: plantarflexion, flexion of great toe
N: tibial n.
Blood supply: posterior tibial a.
Tibialis anterior
O: lateral condyle, superolateral tibia, and interosseous membrane
I: base of 1st metatarsal and medial cuneiform
A: dorsiflexion and inversion
N: deep fibular n.
Blood supply: anterior tibial a.
Extensor hallicus longus
O: anterior fibula and interosseous membrane
I: distal phalanx of 1st digit
A: dorsiflexion, hallus extension
N: deep fibular n.
Blood supply: anterior tibial a.
Extensor digitorum longus
O: lateral tibial condyle, superoanterior fibula, interosseous membrane
I: distal phalanx 2-5
A: dorsiflexion and extension of digits 2-5
N: deep fibular n.
Blood supply: anterior tibial a.
Fibularis tertius
O: inferior third of anterior fibula and interosseous membrane
I: base of 5th metatarsal
A: dorsiflexion and eversion
N: deep fibular n.
Blood supply: anterior tibial a.
Muscles of lateral leg
Fibularis longus
Fibularis brevis
Fibularis longus
O: head and superior 2/3 of lateral fibula
I: base of 1st metatarsal, medial cuneiform
A: plantarflexion, eversion
N: superficial fibular n.
Blood supply: perforating branches of fibular a.
Fibularis brevis
O: lateral fibula
I: base of 5th metatarsal
A: plantarflexion, eversion
N: superficial fibular n.
Blood supply: perforating branches of fibular a.
Pathology of common fibular nerve
The common fibular nerve is easily injured as it passes on lateral aspect of the knee.
Injury affects muscles of lateral and anterior compartment.
Foot drop: condition in which patient is unable to dorsiflex foot –> toes drag on the ground during walking
- paralysis of anterior compartment muscles (dorsiflexors)
Sural nerves
Branches of tibial and common fibular nerves.
Cutaneous innervation to leg
