The Knee

Gastrocnemius

-Muscle located in posterior leg compartment -O: posterior parts of medial and lateral femoral condyles -I: achilles tendon -A: primarily ankle plantarflexor, secondary knee flexor -N: tibial nerve

Soleus

-Muscle located in posterior leg compartment -O: posterior surfaces of the head of the fibula and soleal line -I: posterior calcaneus (by way of the achilles tendon) -A: plantarflexor of ankle -N: tibial nerve Because of the origin, this is considered a muscle of the knee, but primary action is at the ankle

Bursae of knee

-12 or more -Subcutaneous and in the synovial cavity -Subcutaneous: prepatellar and infrapatellar: prepatellar: between the patella and skin infrapatellar: between the superior part of the tibia and the patellar ligament -in synovial cavity: suprapatellar, popliteal, pes anserine, gastrocnemius suprapatellar: located between the inferior part of the femur and and the deep surface of the quadriceps femoris muscle

tibial collateral ligament (MCL-medial collateral ligament)

-An extracapsular ligament of the knee joint -A strong, flat band located on the MEDIAL surface of the knee joint--inherently weaker than LCL-has more loose fibers. -Extends from the medial epicondyle of the femur to the medial condyle and superior part of the medial surface of the tibia -Lower end of the ligament is crossed superficially by the pes anserinus--tendons of the sartorius, gracilis and semitendinosus muscles, all of which strengthen the medial aspect of the joint, cross the ligament -sometimes there is a bursa between this ligament and the tendons of the pes anserinus: bursa anserinus -described as having anterior and posterior bands -weaker than LCL-> often injured in contact sports > part of unhappy triad along with ACL and medial meniscus -deep fibers firmly attached to the medial meniscus -tearing of this ligament also typically results in tearing of the meniscus. Such an injury may occur in contact sports when the knee receives a blow from the lateral side while the foot is fixed on the ground. The force of the blow may also tear the ACL, which is also attached to the medial meniscus. The term "unhappy triad" is applied to a knee injury that involves damage to the three compartments of the knee joint at the same time. -protects against VALGUS (knee knocking) forces of the knee

fibular collateral ligament (LCL-lateral collateral ligament)

-An extracapsular ligament of the knee joint -A strong, rounded (cordlike) ligament on the lateral surface of the joint that extends from the lateral epicondyle of the femur to the lateral side of the head of the fibula -strengthens the lateral aspect of the joint -covered by the tendon of the biceps femoris muscle, an the tendon of the popliteal muscle is deep to it -not fused to the lateral meniscus or capsule--injury to this ligament does not mean that meniscus is damaged as well (unlike in MCL) -MAIN FUNCTION: keep knee STABLE as it moves through full range of motion -protects against varus forces on knee -Stronger than MCL, making it less susceptible to injury

patellar ligament (tendon)

-An extracapsular ligament of the knee joint -continuation of the quadriceps femoris tendon (the portion of the quadriceps femoris tendon that continues form the patella to the tibial tuberosity) -Distal part of the quadriceps tendon -Strong, thick, and fibrous band -Extends from the apex of the patella to the tibial tuberosity -posterior surface of the ligament is separated from the synovial cavity of the knee by the infrapatellar fat pad -ANTERIOR ligament of the knee--strengthens the anterior surface of the joint. -blends with the medial and lateral patellar retinacula -when you flex your knee, this tendon pulls origin from insertion. It is the most tough in flexion.

popliteal fossa

-Diamond shaped space on posterior aspect of the knee -superior borders: biceps femoris and semimembranosus -Inferior borders: heads of the gastrocnemius -Floor: popliteus muscle -superior medial border = semimebranosus -superior lateral border = biceps femoris -inferior medial border = medial head of gastrocnemius -inferior lateral border = lateral head of gastrocnemius -Contents of popliteal fossa: popliteal artery, popliteal vein, tibial nerve, common peroneal nerve

ACL and PCL injuries

-If there is an anterior translation of the tibia (posterior translation of the fibula), then the ACL is injured--excessive anterior extension (hyperextension) -If there is an excessive posterior translation of the tibia (anterior translation of fibula), then the PCL is injured (excessive posterior tibial movement)

patellofemoral joint

-Patella has 3 facets and an intervening medial ridge that articulates with the patellar surface of the femur. -This joint is an articulation between the posterior surface of the patella (where the articular facets are) and the patellar surface of the femur. It is the intermediate component of the tibiofemoral joint. -A plane gliding joint. -The patellar surface of the femur (trochlear groove) represents a gutter into which the posterior patellar surface fits congruently -Femur is covered with articular cartilage -During flexion, the patellar glides inferiorly. Patellofemoral contact migrates superiorly (opposite of patella movement) -During extension, the patella glides superiorly. Patellofemoral contact migrates inferiorly -not a stable joint -lots of weight bearing on this joint

Medial meniscus

-The anterior end (anterior horn) of this semicircular, C-shaped piece of fibrocartilage is attached to the anterior intercondylar area of the tibia, anterior to the ACL -The posterior end (horn) is attached to the posterior intercondylar area of the tibia, anterior to the attachment of the PCL -Firmly adheres to the deep surface of the MCL--articular fibers of the MCL are why meniscal injuries frequently accompany MCL injuries -deepens the articular surface of the tibia -This meniscus is larger than the other one

Menisci (articular discs)

-Two fibrocartilage discs (one medial, one lateral) between the tibial and femoral condyles that help compensate for the irregular shapes of the bones and circulate synovial fluid -Located on articular surface of the tibia -Purpose: deepen the surface--adds to joint congruity; act as shock absorbers for the knee. -Both are thicker at their external margins and taper to thin, unattached edges -Deepens the articular surface of the tibia -ACL and PCL are intracapsular, but extra synovial. These are in the synovial capsule. -Both are firmly attached at their ends to the intercondylar area of the tibia -External margins are attached to the fibrous capsule of the knee joint -Anterior and posterior portions/ends are referred to as horns -Anterior surfaces of medial and lateral are connected to each other by the transverse ligament of the knee -Attached to the margins of the head of the tibia by coronary ligaments

oblique popliteal ligament

-an extracapsular ligament of the knee joint -expansion of the semimembranosus that strengthens the capsule POSTERIORLY (semimembranosus is a posterior muscle). -arises posterior to the medial tibial condyle (where semimembranosus inserts) and passes superolaterally to attach to the central part of the posterior aspect of the fibrous capsule (basically to the lateral condyle of femur) -strengthens the POSTERIOR aspect of the capsule. -checks hyperextension of knee

arcuate popliteal ligament

-an extracapsular ligament of the knee joint -strengthens the fibrous capsule posteriorly -arises from the posterior aspect of the fibular head, passes superiomedially over the popliteus tendon, and spreads over the posterior surface of the knee joint (from fibular head to lateral condyle of femur) -strengthens inferior lateral part of posterior surface -checks hyperextension of knee joint

posterior cruciate ligament (PCL)

-an intracapsular ligament of the knee joint -stronger of the two cruciate ligaments -arises from the POSTERIOR intercondylar area of the tibia and passes superiorly and anteriorly on the medial side of the ACL, and attaches to the lateral surface of the medial femoral condyle. (from lateral to medial) -tightens during flexion of knee joint -prevents posterior sliding of the tibia on the femur (prevents anterior displacement of femur on tibia, or posterior displacement of tibia on fibula)

Anterior cruciate ligament (ACL)

-an intracapsular ligament of the knee joint -the weaker of the two cruciate ligaments -Extends superiorly, posteriorly and laterally from a point anterior to the intercondylar area of the tibia (near top surface of tibia) --> to the posterior part of the medial surface (medial border) of the lateral femoral condyle -Relatively poor blood supply -On slack when the knee is flexed and taut when fully extended -Prevents anterior sliding of the tibia on the femur (Prevents posterior displacement of the femur on the tibia, or prevents anterior displacement of the tibia on the femur)--CHECKS ANTERIOR AND POSTERIOR TRANSLATION ON KNEE -limits hyperextension of the knee! -commonly injured; part of unhappy triad

tibiofemoral joint

-articulation between distal femur and proximal tibia -superior surfaces of the tibia, the medial and lateral tibial plateaus, articulating with the medial and lateral femoral condyles -relatively weak mechanically due to articular surfaces -all articular surfaces covered with hyaline cartilage -intercondylar emincence on tibia fits into intercondylar notch of femur -condyles of femur are convex and represent surfaces to articulate with the corresponding facets on the tibial facet -facets are shallow, so the bony congruence of this joint is poor. -Menisci increase congruence

Lateral tibial rotation

-done by biceps femoris (a hamstring muscle; posterior thigh compartment) -occurs during locking-response of biceps femoris

medial tibial rotation

-done by popliteus muscle (posterior thigh compartment) -contracts and causes medial rotation of the tibia -occurs during unlocking--response of popliteus

articular capsule (knee joint)

-fibrous capsule -attaches to the femur superiorly, just proximal to the articular margins of the condyles -attaches posteriorly the intercondylar fossa (notch) of femur. -attaches inferiorly to articular margin of tibia -absent anterior to allow synovial membrane to "pouch" superiorly creating suprapatellar bursa -this fibrous capsule is very strong because of hte poor joint congruence of the knee -medial and lateral is strengthened by the lateralis and the medialis expansions

Blood supply to knee

-genicular branches from several arteries form the genicular anastomosis around the knee -genicular branch branches off of the femoral artery -knee receives innervation from the branches of the obturator nerve, femoral nerve tibial nerve, and common peroneal nerve -obturator and femoral come from the lumbar plexus -tibial and common fibular come from the sacral plexus

Knee joint

-intermediate joint of lower limb -A hinge type of synovial joint -one degree of freedom -allows flexion and extension in the sagittal plane about coronal axis -consists of articulations between the distal femur and proximal tibia (tibiofemoral joint); patella and femur (patellofemoral joint). -3 joints within a single synovial cavity: lateral tibiofemoral joint, medial tibiofemoral joint, intermediate patellofemoral joint.

cruciate ligaments

-intracapsular ligaments of the knee joint -ACL and PCL -these two ligaments within the articular capsule connect to the tibia -named based on their origins relative to the intercondylar area of the tibia. From their origins, they cross (Cruciate=cross) on their way to their destinations on the femur. -They join the femur and the tibia -crisscross within the articular capsule -located in the center of the joint and cross each other obliquely like an "X" -both provide stability to the knee joint -"crux" = latin for cross

tibiofibular joints

-joints connecting the tibia and fibula -there are two of these joints: a proximal one and a distal one -Synovial plane gliding joints

anterior tibiofibular ligament

-ligament of the proximal tibiofibular joint -consists of two or three broad flat bands that pass superiomedially from the anterior aspect of the fibular head to the anterior part of the lateral tibial condyle

posteriortibiofibular ligament

-ligament of the proximal tibiofibular joint -single broad band that passes superomedially from the posterior aspect of the fibular head to the posterior part of the lateral tibial condyle

Transverse ligament

-ligament that joins the anterior edges of the menisci (joins medial and lateral menisci together) -located on anterior side of knee joint -permits menisci to move together during knee movements

posterior meniscofemoral ligament

-ligament that joins the lateral meniscus to the PCL and the medial femoral condyle -passes to the medial side of the ACL -A in picture

Synovial Membrane

-lines internal aspect of the fibrous capsule -this synovial cavity is the largest joint space in the body

popliteus

-muscle located in posterior compartment of leg -O: anterior lateral condyle of femur -I: posterior surface of tibia near soleal line -A: internal rotation of knee joint, unlocks extended knee, weak knee flexor -N: tibial nerve

Plantaris

-muscle located in posterior leg compartment -O: distal end of lateral supracondylar line (on femur) -I: posterior calcaneus -A: works with gastrocnemius to plantarflex the ankle and assist in flexion of the knee -N: tibial nerve -very minor role in plantar flexion and knee flexion -the tendon is used for transplants to the hand without significant, resultant disability

Lateral meniscus

-nearly circular piece of fibrocartilage -Its anterior end is attached anteriorly to the intercondylar area of the tibia, and laterally and posteriorly to the ACL -its posterior end is attached posteriorly to the intercondylar area of the tibia, and to the posterior end of the medial meniscus -Not attached to the LCL-tendon of the popliteus separates the lateral meniscus from the LCL -more freely moveable than the medial meniscus, because it does not attach to the LCL

proximal tibiofibular joint

-synovial joint between the head of the fibula and the lateral condyle of the tibia -Articular surface: flat facet on the fibular head articulates with a similar articular facet located posteriorlaterally on the lateral tibial condyle -articular capsule is fibrous and surrounds the joint. This capsule attaches to the margins of the articular surfaces of the tibia and fibula. -The only moving of this joint is gliding which occurs during DORSIFLEXION AND PLANTARFLEXION of the ankle!!! -Ligaments: anterior tibiofibular ligament and posterior tibiofibular ligament -no muscle is the prime mover of this joint -Blood supply: arteries of the joint are from the inferior lateral genicular and anterior tibial recurrent arteries -Nerve supply: from the fibular nerve (common peroneal) and the nerve to the popliteus--Branches of sciatic nerve.

patellar retinaculum

-tissue expansions of the vastus medialis and vastus lateralis -provide support to the articular capsule -Medial and lateral -These fused tendons of insertion of the quadriceps femoris muscle and the fascia lata (fascia of thigh) strengthen the anterior surface of the joint -3 and 5

Genu varum

Bowleg

Genu valgus

Knock nee

patella

a small, triangular bone located anterior to the knee joint. -A sesamoid bone (the largest sesamoid bone) that develops in the tendon of the quadriceps femoris muscle. -functions: to increase the leverage of the tendon of hte quadriceps femoris muscle, to maintain the position ofhte tendon when the knee is flexed, and to protect the knee joint.

patellar ligament

attaches the patella to the tibial tuberosity

gastrocnemius bursa

bursa that protects the medial head of the gastrocnemius muscle

Coronary ligaments

capsular fibers attaching the margins of the menisci to the tibial condyles

apex of patella

pointed distal end of patella

articular facets of patella

posterior surface of patella contains two of these, one to articulate with the medial condyle of the femur and the other to articulate with the lateral condyle of the femur

suprapatellar bursa

subcutaneous bursa located between the inferior part of the femur and the deep surface of the quadriceps femoris muscle

prepatellar bursa

subcutaneous bursa located between the patella and the skin

infrapatellar bursa

subcutaneous bursa located between the superior part of the tibia and the patellar ligament

popliteus bursa

synovial cavity bursa located between the popliteus muscle and the lateral tibial condyle

base of patella

the broad proximal end of the patella.