Knee Joint

The patella's posterior surface is shaped to articulate with the patellar surface at the distal end of the femur. The patella's posterior surface is covered by

hyaline cartilage

When does the suprapatellar bursa swell? Why?

the suprapatellar bursa swells when excessive fluid accumulates in the knee joint's synovial cavity as a consequence of injury or disease because the suprapatellar bursa is a region of the knee joint's synovial cavity

The distal end of the femur articulates with the

tibia and patella in the knee Joint

medial and lateral menisci are

two discs of fibrous cartilage that also contribute articular surfaces They are between the femur and tibia in the knee joint

The valgus force also widens ________ and stretches the ______

widens the medial joint space of the knee joint and thus stretches the medial collateral ligament (the MCL).

Medial and lateral collateral ligaments Purpose:

stabilize the medial and lateral sides of the knee joint by restricting side-to-side movements of the leg at the knee joint.

The PCL is attached to the ___ femoral condyle.

superiorly to the *anterior part* of the lateral surface of the *medial femoral condyle.* PM: PCL to Medial

The ACL is attached to the ___ femoral condyle.

superiorly to the *posterior part* of the medial surface of the *lateral femoral condyle* AL: ACL to Lateral

The deep depression between the femoral condyles in the BACK of the distal end of the femur is called?

the intercondylar notch or fossa

Purpose of menisci in knee joint What type of surface is the menisci (concave or convex?) What is the meniscotibial surface?

Each meniscus improves the fit of its tibial condyle with the femoral condyle above. This is because each meniscus presents a sharply concave surface to the sharply convex surface of the femoral condyle above. The combined articular surface that each meniscus and its tibial condyle presents to the femoral condyle above is called, by orthopedists, the meniscotibial surface of the meniscus and tibial condyle. The drawing on the right shows the shape of the meniscotibial surfaces.

Upper and lower ends of menisci Attached or free? What is the exception? What bathes the surfaces?

Except at the horns, the upper and lower surfaces of each meniscus are also free and unattached. The knee joint's synovial fluid bathes both the upper and lower free surfaces of the menisci.

What intervenes between the patellar ligament and synovial membrane of the joint?

FAT PAD This fat pad is called the infrapatellar fat pad because it lies below the lower border of the patella.

What type of tear could be caused by a valgus force?

MCL (sometimes medial or lateral meniscus) Recent studies suggest that the medial meniscus is more commonly torn if the ACL (that is, the anterior cruciate ligament) has been weakened by previous, chronic injury; the lateral meniscus is more commonly torn if the ACL has not been weakened by previous injury.

Which bone in the leg is medial and which one is lateral? Which bone is considered the weight-bearing bone of the leg?

Medial = tibia Lateral = fibula Tibia is considered the weight bearing bone

Which femoral condyle is more rounded?

Medial Femoral condyle

What are the parts of the proximal tibia that articulate with the condyles of the femur? They are covered by?

Medial and lateral TIBIAL condyles Covered by hyaline cartilage

Four Major Ligaments of the knee

Medial and lateral collateral ligaments Anterior and posterior cruciate ligaments

What are the knobs on the distal end of the femur that articulate with the tibia called? What articulates with the patella?

Medial and lateral femoral condyle Smooth depression between the femoral condyles in front of the distal end of the femur (patellar surface) PS. Red lines mark the margin of attachment of the synovial membrane of the knee joint. Green lines mark the margin of attachment of the fibrous capsule.

Do the ACL and PCL lie in the joints synovial cavity?

NO; In other words, they are not bathed by the synovial fluid of the joint's synovial cavity. Black line: Margins of attachment of the synovial membrane to the tibial plateau. The darkened area of the tibial plateau marks the region of the tibial plateau that is bathed in synovial fluid; the synovial fluid can be seen to bathe the menisci but not the cruciate ligaments.

Do the three bursae swell when theres excessive fluid accumulates in the synovial cavity?

NO; because they do not communicate with the synovial cavity

Outer edge of menisci vs inner edge of menisci Which one is broad and attached? which ones is thin and unattached?

Outer edge of each meniscus is relatively broad and attached to the deep surface of the joint's fibrous capsule The inner edge of each meniscus is sharp and unattached.

What type of bone is the patella? Where do these types of bones develop? The patella forms within the _________ tendon, which envelopes the patella EXCEPT for the __________ surface.

Sesamoid bone Sesamoid bones are bones that develop within the tendons of muscles Patella forms within the Quadraceps femoris tendon which envelopes the tendon except for the peosterior surface

Three articulations of the knee joint

-Medial side of joint: medial femoral condyle with the meniscotibial surface of the medial menisci and medial tibial condyle -Lateral side of joint: lateral femoral condyle meniscotibial surface of the lateral menisci and lateral tibial condyle -Anterior aspect of the joint: patellar surface of the femur articulates with the posterior surface of the patella

Three major bursae that lie anterior to the knee joint and NONE of them communicate with the joints synovial cavity

1. The prepatellar bursa is a subcutaneous bursa that lies between the skin and (a) the lower half of the patella and (b) the upper half of the patellar ligament. 2. The superficial infrapatellar bursa is a subcutaneous bursa that lies between the skin and the patellar ligament. 3. The deep infrapatellar bursa is an intracapsular bursa that lies between the patellar ligament and the infrapatellar fat pad.

Articularis Genu is where? What does it do?

A small, deep muscle in the anterior part of the thigh called articularis genus extends from the shaft of the femur to the upper end of the suprapatellar bursa. Articularis genus pulls upward on the suprapatellar bursa when the quadriceps femoris muscles act to extend the leg at the knee.

Common for a player to be hit on the lateral aspect of the knee which leads to a medially directed force on the knee. A medially directed force --> (abduction/adduction) of the knee Called the:

Abduction This is called the valgus force

gastrocnemius bursa

Bursa lies posterior to the knee joint Communicates directly with the synovial cavity

Bursae establish a fluid-filled discontinuity between adjacent tissues which permits.....

Bursae essentially establish a fluid-filled discontinuity between adjacent tissues; the discontinuity permits the adjacent tissues to freely slide past each other over a limited distance.

The ACL restricts:

In the knee joint, the anterior cruciate ligament restricts the tibia from being *pulled too far forward during leg extension at the knee*

Knee Joint is a ________ joint in which the ___, ____, and _____ contrivute articular surfaces

Synovial joint -Femur, tibia, patella

Lateral Collateral Ligament (LCL) extends from ______ to ________ Attached to the:

The lateral collateral ligament extends from the lateral epicondyle of the femur to the head of the fibula. Only the superior part of the lateral collateral ligament is attached to the knee joint capsule. The lateral collateral ligament is not attached to the lateral meniscus.

What is the tibial tuberosity?

The prominence that projects forward from the anterior surface of the tibia just below the tibial plateau is called the tibial tuberosity. The tibial tuberosity is the site at which the quadriceps femoris tendon inserts onto the tibia.

Suprapatellar bursa

This synovial membrane-lined recess that is the most anteriosuperior part of the knee joint's synovial cavity that lies between the quadriceps femoris and distal end of femur it extends (in an adult) for about 5 to 7 cm above the upper border of the patella.

unhappy triad

Torn MCL --> torn medial meniscus --> stretching of ACL --> tear of ACL "complete tearing of the MCL frees the valgus force to widen the medial joint space even more. As the medial joint space markedly widens, the ACL may become so severely stretched over the medial aspect of the lateral femoral condyle that the midportion of the ligament suffers an abrupt rupture. The triad of a completely torn MCL, a ruptured ACL, and a torn meniscus is called the "unhappy triad."

Bakers Cyst

accumulation of synovial fluid in the knee joint --> swelling in the gastricnemius bursa in the back of the knee A Baker's cyst is almost always a complication of chronic swelling of the knee joint's synovial cavity, such as may occur with rheumatoid arthritis of the knee.

The medial collateral ligament extends from the _______ to the ________ It is attached to:

extends from the medial epicondyle of the femur to the medial tibial condyle and the medial surface of the tibial shaft; the ligament is attached to both the capsule of the knee joint and the medial meniscus.

What is a bursa? The wall of a bursa consists of _______ supported externally by _________

flattened, fluid filled sac The wall of a bursa consists of an internal synovial membrane supported externally by dense connective tissue.

Both the ACL AND PCL are attached (in tibia): ACL is attached to: PCL is attached to:

inferiorly to the intercondylar area between the menisci and the hyaline-cartilage covered surfaces of the tibial condyles. The anterior cruciate ligament is attached to the anterior part of the intercondylar area, and the posterior cruciate ligament is attached to the posterior part of the intercondylar area.

In between the tibial condyles there is a projection upward called the ____

intercondylar eminence

tibial plateau is

intercondylar eminence + tibial condyles

The PCL restricts

posterior cruciate ligament restricts the tibia from being *pulled too far backward during leg flexion at the knee.*

Anterior and posterior cruciate ligaments (purpose):

restrict anterior-to-posterior movements of the leg at the knee joint. The ligaments are called cruciate ligaments because they cross each other within the knee joint as they extend from the tibia plateau below to the femoral condyles above