synovial membrane and bursa

SYNOVIAL MEMBRANE

- the synovial membrane of the knee joint is very extensive and the synovial cavity of the knee is the largest in the body

Femur

 attaches along the margins of the articular cartilage of the distal femur; medially, anteriorly, laterally, and posteriorly

- are two attachments at the inferior edge of the intercondylar notch; one from the apex of the patella and one from the anterior edge of the tibial posterior intercondylar sulcus

 Menisci

 the synovium attaches to the external edges of the menisci and passes to the margins of the articular cartilage of the femoral and tibial condyles and the patella

Patella

- attaches along the margins of the articular cartilage on the posterior surface

 from the superior border of the patella to the superior edge of the patellar surface of the femur

- here it forms the suprapatellar bursa which extends superiorly, deep to the quadriceps femoris muscle

 from the inferior edge / apex of the patella to the inferior edge of the intercondylar fossa of the femur, the synovium passes inferoposteriorly

- here it forms the infrapatellar fold

 from the medial and lateral margins of the patella, the synovium passes superiorly to the corresponding edges of the patellar surface of the femur, and inferiorly to the anterior superior edges of the menisci and the anterior intercondylar sulcus of the tibia (where menisci are not present)

Infrapatellar Fat Pad

- adipose tissue which separates the synovium from the patellar ligament

- the synovium lines this fat pad on its posterior side

- the synovium projects posteriorly into the joint

Alar Folds

- two fringe-like structures that meet in the center, at the infrapatellar fold

- formed by the synovium as the alar folds line the infrapatellar fat pad and pass from the patella to the menisci and tibia

 Infrapatellar Fold

- extends from the apex of the patella to the inferior margin of the

intercondylar fossa of the femur

- where the alar folds meet (centrally)

Tibia

 attaches along the margins of the articular cartilage on the superior surface; it invaginates along the anterior and posterior intercondylar sulci

Anterior Intercondylar Sulcus

- the synovial membrane invaginates slightly from the anterior edge to line the posterior aspect of the infrapatellar fat pad

- passes superiorly to the patella from the central area or to the menisci from the articular margins

Posterior Intercondylar Sulcus

- the synovial membrane invaginates to line the anterior, medial and lateral aspects of both cruciate ligaments, so the posterior aspect of the capsule is not lined by synovium

- this part of the synovial membrane passes to the inferior edge of the intercondylar notch of the femur from the margins of the sulcus or to the inferior meniscal edges from the posterior articular margins of the sulcus

BURSAE OF THE KNEE

- there are many bursae associated with the knee joint, these are the more common ones

- inflammation of a bursa is called bursitis

function of the bursa of the knee

allow free movement of the structures that are separated

Suprapatellar Bursa

- a large extension of the knee joint synovium deep to the quadriceps femoris muscle

- separates the quadriceps femoris tendon from the femur

- suprapatellar bursitis can be a feature of knee joint effusion i.e. “water on the knee”

(Subcutaneous) Prepatellar Bursa

- in the superficial fascia over the patella

- separates the skin from the patella

- inflammation of this bursa is prepatellar bursitis i.e. “housemaid’s knee”

Subcutaneous Infrapatellar Bursa / Superficial Infrapatellar Bursa

- in the superficial fascia over the patellar ligament and the tibial tuberosity

- separates the skin from the patellar ligament and from the tibial tuberosity

- inflammation of this bursa is subcutaneous infrapatellar bursitis i.e. “clergyman’s

knee”

Deep Infrapatellar Bursa

- between the patellar ligament and the anterior surface of the proximal tibia,

superior to the tibial tuberosity

- separates the patellar ligament from the tibia

Anserine Bursa / Bursa Anserina

- located between the medial collateral ligament of the knee and the pes anserinus,

also around the individual tendons of the pes anserinus as they insert at the

proximal medial tibial shaft

- separates the ligament from tendons and the tendons from each other

Semimembranosus Bursa (not pictured)

- located between the semimembranosus muscle and the medial head of the

gastrocnemius muscle at the area of the medial condyle of the femur

 Popliteus Bursa (not pictured)

- located between the popliteus tendon and the lateral condyle of the tibia

- continuous with the knee joint inferior to the lateral meniscus

Gastrocnemius Bursa (not pictured)

- located between the medial head of gastrocnemius muscle and the knee joint

- often communicates with the semimembranosus bursa

- may communicate with the knee joint