Tibiofemoral Joint

Question 1

State the type of joint:

Tibiofemoral joint

Answer 1

Bi-condylar, synovial modified hinge joint, biaxial - capable of 2 degrees of freedom

Question 2

Briefly describe the femoral articular surface

Answer 2

Covers the ends of the medial and lateral condyles of the distal femur which are convex A-P and transversely and is covered in thick hyaline cartilage. lateral condyle is shorter and wider than the medial. Intercondylar notch is continuous superiorly with trochlear groove. Faint grooves separate condylar & patellar surface centrally, with patella surface divided by well-marked groove into a larger lateral buttress wall and smaller medial wall

Question 3

Give the attachments & function of the collateral ligaments of the knee

Answer 3

Medial Collateral Ligament - strong band extends from medial femoral epicondyle, and attaches to the Medial knee joint capsule, medial meniscus, medial tibial condyle and anteromedial aspect of the tibial shaft at level of tibial tuberosity

Lateral Collateral Ligament - round cord (5cm) attaches to the lateral epicondyle of the femur, and attaches to head of fibula bificating the Biceps femoris tendon

Provide mediolateral stability and become taught in extension

Question 4

How many articulations are at the knee joint

Answer 4

3 articulations

Question 5

Briefly describe the tibial articular surface

Answer 5

Medial and lateral condyles on the superior aspect of the tibia/tibial plateau covered in hyaline cartilage, concave centrally and flatter in the periphery for attachment of menisci. Condyles separated by intercondylar eminences. Medial surface is larger A-P

Question 6

Give the attachments and direction of the ACL

Answer 6

Attaches to the anterior intercondylar area of tibia and passes superb-laterally and posteriorly to attach to the postero-medial part of the surface of the lateral femoral condyle

Question 7

Give the attachments and direction of the PCL

Answer 7

Attaches to the posterior intercondylar area of the tibia. It passes supero-medially and anteriorly to attach to the antero-lateral part of the surface of the medial femoral condyle

Question 8

What does the ACL and PCL prevent

Answer 8

ACL - prevents (86%) anterior displacement of the tibia on the femur, prevents (30%) medial displacement
PCL - prevents (94%) posterior displacement of the tibia on the femur, prevents (36%) lateral displacement

Question 9

Describe the menisci

Answer 9

• Semi-lunar plates of fibrocartilage
  
  • Medial ‘C’ shaped - firmly adherent to deep surface of tibial collateral ligament
  • Lateral ‘O’ shaped - separated from fibular collateral ligament
  • 2 horns per menisci - anterior and posterior
  • Medial less mobile and therefore more easily damaged - due to blending into medial joint capsule and MCL
  • Outer borders thick and vascular - recovers
  • Inner borders thin and avascular - tends not to recover; becomes mechanical block, i.e pseudo/real locking.

Question 10

Give Medial meniscus attachments

Answer 10

Anterior horn
Most anterior facet of anterior intercondylar area + ACL
Transverse (intercondylar) and coronary ligaments

Posterior horn
Facet of posterior intercondylar area posteromedial to posterior horn of lateral meniscus but anterior to PCL
Blends with medial knee joint capsule and medial collateral ligt

Question 11

Give lateral meniscus attachments

Answer 11

Anterior horn
Small facet on anterior intercondylar eminence posterior to ACL
Transverse and coronary ligaments

Posterior horn
Most anterior facet of posterior intercondylar area - anteriorly to posterior horn of medial meniscus

Question 12

Give meniscal function

Answer 12

• Enhances tibio-femoral joint stability by deepening tibial articular surface - increasing congruence
  
  • Act as shock absorbers - hydrostatic and fibroelastic
  • Conforms to changing shape of femoral condyles during knee movement

Question 13

Give joint capsule attachments

Answer 13

No complete independent fibrous capsule: knee surrounded by thick ligamentous sheath of muscle tendons & their expansions

Anteriorly: Capsular attachment to femur is deficient; replaced by quadriceps femoris tendon so tibial attachment is more complete only deficient in area of tibial tuberosity

Posteriorly; true capsular fibres pass vertically above articular surface to posterior border of tibia; strengthened by oblique popliteal ligament (expansion of semimembranosus tendon)

At sides: Capsular fibres pass from femoral to tibial condyles, blending posteriorly with ligamentous network & anteriorly with tendinous expansions of quadriceps femoris; lower lateral capsule strengthened by arcuate popliteal ligament from fibula head

Synovial membrane lines the joint capsule attaching to articular margins of the femur, tibia and patella. On the tibia it is reflected forward around the cruciate ligaments so that they are intracapsular but extrasynovial. Above patella between the femoral shaft and quadriceps femoris synovial membrane extends 6 cm as the suprapatellar bursa, to which are attached a few muscle fibres from vastus intermedius. Synovial recesses extend behind each femoral condyle and deep to the popliteus tendon. Bursae associated with tendons crossing the joint do not communicate directly with the joint space.

Question 14

Give names of the bursae surrounding the knee joint

Answer 14

• Suprapatellar bursa
  
  • Prepatellar bursa
  • Superficial Infrapatellar bursa
  • Deep infrapatellar bursa
  • Pes anserinus bursa
  • Semimembranosus bursa

Fluid filled sacs preventing unwanted friction between bones, muscles and bones, bones and ligaments