Knee Flashcards
Tibia
- Long bone with a diaphysis and a proximal and distal epiphyses
- Transfers majority of weight between femur and talus
Tibia articulates with
- Femur
- Fibula
- Talus
Structures at anterior proximal end of tibia
- Medial/lateral condyle
- Intercondylar eminence
- Anterior/posterior intercondylar surface
- Tibial tuberosity
- Gerdy’s tubercle
Medial condyle of tibia
- Larger with larger articular surface
- Oval shaped
Lateral condyle of tibia
- Smaller than medial
- Circular shaped articular surface
Intercondylar eminence
- Located between condyles
- Medial and lateral intercondylar tubercles
Anterior and posterior intercondylar surface
- Attachment of cruciate ligaments
Tibial tuberosity
- Attachment of patellar ligament
Gerdy’s tubercle (tubercle of the iliotibial tract)
- Small projection
- Lateral to tibial tuberosity and patellar apex (when knee is extended)
- IT tract attaches
Structures at posterior proximal end of tibia
- Groove for semimembranosus tendon
- Fibular articular facet
Groove for semimembranosus tendon
- Posteromedial edge of medial condyle
Fibular articular facet
- Facet on lateral condyle
- Articulates with fibular head
Fibula
- Long slender bone
- IMPORTANT for ankle stability
- Transmits small amounts of weight (~15%)
- Site of muscle attachment
Fibula articulates with
- Tibia
- Talus
Proximal fibula structures
- Head of fibula
- “Square-ish” in shape
- Subcutaneous, easily palpated
- Common fibular nerve
- Articular facet
- Apex of fibula (styloid process)
Common fibular nerve passes
- Around fibular head/neck
- Easily damaged
Articular facet of proximal fibula
- Articulates with lateral condyle of tibia
Patella
- Sesamoid bone in quadriceps tendon
- Superficial, easily palpated
- Increases mechanical advantage of quadriceps muscles
Patella articulates with
- Femoral condyles to form the patellofemoral joint
- Triangular in shape
Apex of patella
- Pointed inferior end
- Just proximal to knee joint line when knee is extended
Base of patella
- Wide superior end
- Outer border is rough b/c of tendon/ligament attachment
Patella development
- 1 or 2 ossification centers that appear between 3-6th year
- Fusion at puberty
Lack of patella fusion
- Bipartite patella
Patella posterior surface
- Smooth
- Covered with thick articular (hyaline) cartilage in a living person
Articular facets of patella
- Separated by a vertical ridge
- Medial facet
- Lateral facet
- Odd facet
Medial facet of patella
- Articulates with medial femoral condyle
Lateral facet of patella
- Larger
- Articulates with the lateral femoral condyle
Odd facet of patella
- Most medial aspect of medial facet
Patella stabilized by
- Medial and lateral retinacula
- Multi-layered connective tissue structure
Patella retinacula attach to
- Patella
- Tibia
- Femur
Patella retinacula derived from neighboring structures
- Crural fascia
- MCL (medial side
patellofemoral and patellotibial ligaments: medial and lateral sides) - IT band (lateral side)
- Quadriceps aponeurosis (medial and lateral sides)
Genu varus
- Leg angled inward
- Knee shifted laterally
- Apex of deformity is lateral
Genu valgus
- Leg angled outward
- Knee shifted medially
- Apex of deformity is medial
Normal development of knee
- Varus until about 2 years
- “Physiological bowing”
- Valgus at age 3
- Degree of valgus decreases to adult level by age 7
- Remains slightly valgus
Knee joint consist of articulations between
- Femur and patella (patellofemoral joint)
Characteristics of knee condyles
- Medial/lateral femoral condyles: convex
- Medial/lateral tibial condyles: concave
Knee joint
- Modified hinge joint
- Combination of gliding, pivot, and hinge joints
Knee joint (modified hinge joint) allows for
- Rotation in sagittal plane: flexion/extension
- Rotation in transverse plane: internal and external rotation
- Translation in sagittal plane
Muscles surrounding knee are most important in
- Stability
Knee joint capsule is reinforced by
- Ligaments posteriorly and laterally
Anterior knee joint capsule is formed by
- Patellar ligament
- Medial and lateral retinacula
Synovial membrane (lines joint capsule) attaches to
- Articular margins of the patella, femoral cartilage, and meniscal edges
Synovial membrane covers
- Cruciate ligaments anteriorly
- Posterior aspect of the infrapatellar fat pad
Cruciate ligaments and posterior aspect of the infrapatellar fat pad are considered
- Intracapsular but extra-synovial
- Outside the synovial space
Infrapatellar fat pad
- Adipose found inferior to patella
- Deep to patellar ligament
- Between patellar tendon and synovial membrane
Infrapatellar plica (ligamentum mucosum)
- Synovial fold
- Embryological remnant of knee joint division
- Other plica:
- Suprapatellar
- Medial and lateral patellar
Menisci of knee
- Crescent shaped fibrocartilage plates
- Intracapsular, intrasynovial (outer surface is not intrasynovial)
- Thicker at periphery, thin centrally
Menisci function
- Improve congruency between tibia and femur
- Shock absorption
- Load dispersion
Menisci attachments
- Attached to tibia via coronary ligaments
- Connected by transverse ligament of knee anteriorly
Anterior/posterior horns of menisci
- Each attaches to the intercondylar area
Medial meniscus
- “C”-shaped
- Less mobile
- Attached to MCL
- Wider posterior than anterior
Lateral meniscus
- More circular in shape
- Covers a large portion of lateral condyle
- More movable
- Uniform width
- Broader than medial meniscus
- Popliteus attaches and is located posterolaterally
Menisci vascularity
- Outer 25% well vascularized
- Inner is nourished by synovial fluid
Extracapsular and capsular ligaments of knee
- Patellar ligament (anteriorly)
- Retinacula anteromedially and anterolaterally
Fibular collateral ligament (lateral collateral ligament of knee)
- Extracapsular
- Lateral epicondyle to apex of fibular head (at biceps femoris insertion)
- Narrow, rope like ligament
Fibular collateral ligament (LCL) resists
- Varus stress to knee
- Taut in extension
Tibial collateral ligament (medial collateral ligament of knee)
- Medial epicondyle to medial tibial condyle and tibial shaft
- Broad ligament that blends with the capsule (capsular ligament)
- Attaches firmly to medial meniscus
Damage to MCL
- Usually causes damage to medial meniscus as well
MCL resists
- Valgus stress to knee
- Taut in extension
Oblique popliteal ligament
- Capsular ligament
- Blends with and supports the posterior capsule
- Extension from semimembranosus tendon
- Attaches to lateral femoral condyle
Arcuate popliteal ligament
- Capsular ligament
- Y-shaped ligament
- Attaches to apex of fibula and divides into 2 limbs
- Supports posterolateral knee
Division of arcuate popliteal ligament
- Medial limb curves over popliteus muscle and blends with oblique popliteal ligament (also attaches to tibia)
- Lateral limb blends with lateral capsule
Intracapsular ligaments of knee
- Within capsule
- Extrasynovial (outside synovium)
Cruciate ligaments
- Resist anterior/posterior translation and rotation
- Guide movement
Anterior cruciate ligament attaches
- Anterior intercondylar fossa of tibia to medial side of lateral femoral condyle in intercondylar notch
- Travels in a superior posterolateral direction
Anterior cruciate ligament resists
- Posterior displacement of femur (anterior displacement of tibia
- Knee hyperextension(taut in extension
Posterior cruciate ligament
- Thicker and stronger than ACL
Posterior cruciate ligament attaches to
- Posterior intercondylar fossa of tibia to lateral side of medial femoral condyle in intercondylar notch
- Travels in a superior anteromedial direction
Posterior cruciate ligaments resist
- Anterior femur displacement (or posterior tibial displacement
- Knee hyperflexion
Extracapsular ligaments of knee
- Fibular collateral ligament (LCL)
Capsular ligaments of knee
- Tibial collateral ligament (MCL)
- Oblique popliteal ligament
- Arcuate popliteal ligament
Intracapsular ligaments of knee
- Anterior cruciate ligament (ACL)
- Posterior cruciate ligament (PCL)
- Transverse ligament (transverse genicular ligament)
- Meniscofemoral ligaments
- Meniscotibial ligaments (coronary ligaments)
Transverse ligament of the knee (transverse genicular ligament)
- Not always present
- Attaches to anterior horn of medial meniscus and anterior margin of lateral meniscus
Meniscofemoral ligaments
- Span from the posterior horn of lateral meniscus to the lateral aspect of medial femoral condyle
- Named based on their relationship to the PCL
Meniscofemoral ligaments (names)
- Anterior meniscofemoral ligament (Ligament of Humphrey)
- Posterior meniscofemoral ligament (Ligament of Wrisberg)
Anterior meniscofemoral ligament (Ligament of Humphrey)
- Anterior to PCL
Posterior meniscofemoral ligament (Ligament of Wrisberg)
- Posterior to PCL
Meniscotibial ligaments (coronary ligaments)
- Attach to menisci periphery and tibial plateau
- Also anchors horns of menisci to tibia
Popliteus
- Partially intracapsular and extracapsular
- Proximal tendon is found between LCL and lateral meniscus
- Covered by fascia derived from semimembranosus
Popliteus origin
- Lateral femoral condyle (popliteal groove)
- Lateral meniscus
- Knee joint capsule
Popliteus insertion
- Superior to soleal line (tibia)
Popliteus innervation
- Tibial nerve
Popliteus blood supply
- Posterior tibial artery
- Medial inferior genicular artery
Popliteus function
- Unlocks knee by laterally rotating femur on tibia or medially rotating tibia on femur
- Pulls meniscus posteriorly
Knee movement
- Mostly flexion and extension
- Rotation in sagittal plane
- Some medial and lateral rotation
- Rotation in transverse plane
Translation
Open kinetic chain (foot off the ground) during knee extension
- Tibia glides (translates) anteriorly on femur
- Last 15-20ᵒ of extension, tibia rotates externally on femur
Open kinetic chain (foot off the ground) during knee flexion
- Tibia glides posteriorly on femur
- First 15-20ᵒ of flexion, tibia rotates internally on femur
Closed kinetic chain (foot is on the ground) during knee extension
- Femur translates posteriorly on stable tibia
- Last 20ᵒ femur rotates internally on tibia
Closed kinetic chain (foot is on the ground) during knee flexion
- Femur glides anteriorly on tibia
- First 20ᵒ femur rotates externally
Screw home mechanism
- Occurs last 15-20ᵒ of knee extension
- Medial tibial plateau is longer, movement continues on medial side
- Position of maximal stability, ligaments are taut
Muscles of knee extension
- Rectus femoris
- Vastus lateralis
- Vastus intermedius
- Vastus medialis
Muscles of knee felxion
- Biceps femoris (long/short heads)
- Semitendinosus
- Semimembranosus
- Gracilis
- Sartorius
- Popliteus
- Plantaris
Muscles of knee internal (medial) rotation (when knee is flexed)
- Gracilis
- Sartorius
- Semitendinosus
- Semimembranosus
- Popliteus
Muscles of knee external (lateral) rotation (when knee is flexed)
- Biceps femoris
- Long head
- Short head
Knee blood supply
- Genicular anastomoses
- Intracapsular structures supplied by genicular anastomoses and middle genicular artery
Knee nerve supply: articular branches from
- Femoral nerve (posterior division)
- Muscular branches and saphenous nerve
- Tibial
- Common fibular
- Obturator (posterior division)
Knee bursae function
- Prevent friction between structures during movement
Anterior knee bursae (names)
- Prepatellar bursa
- Superficial infrapatellar bursa
- Deep infrapatellar bursa
- Suprapatellar bursa
Prepatellar bursa
- Located in the superficial fascia between patella and skin
- Bursitis: housemaid’s knee
Superficial infrapatellar bursa
- Between tibial tuberosity and skin
- Bursitis: Clergymans knee
Deep infrapatellar bursa
- Between tibial tuberosity and patellar ligament
- Bursitis: Clergymans knee
Suprapatellar bursa
- Superior extension of synovial membrane of the knee joint
- Between femur and quadriceps tendon
- Communicates with knee joint
Medial knee bursa
- Anserine bursa
Anserine bursa
- Between pes anserinus and MCL
- Extends between tendons of the pes anserinus
Lateral knee bursae
- Between LCL and biceps femoris
- Between LCL and popliteus tendon
Posterior knee bursae
- Popliteal bursa
- Medial gastrocnemius bursa
- Lateral gastrocnemius bursa
- Semimembranosus bursa
Popliteal bursa
- Between popliteal tendon and lateral condyle of tibia
- Communicates with knee joint joint
Medial gastrocnemius bursa
- Between medial head of gastrocnemius and joint capsule
- Can communicate with joint cavity
Lateral gastrocnemius bursa
- Between the lateral head of the gastrocnemius and joint capsule
- Can communicate with joint cavity
Semimembranosus bursa
- Between semimembranosus tendon and medial head of gastrocnemius and medial femoral condyle
- Can communicate with joint cavity and medial gastrocnemius bursa
Medial meniscus (clinical)
- Commonly injured with MCL
- More commonly injured than LCL
Unhappy triad (O’Donoghue triad) is disruption in the
- MCL
- Medial meniscus
- ACL
Unhappy triad (O’Donoghue triad) is often caused by
- Valgus stress induced by a lateral blow to the knee
ACL tear
- Anterior drawer test is (+)
- (+) Lachmans test
PCL tear
- Posterior drawer test is (+)
