the knee

• knee joint

  • Synovial bicondylar hinge joint - condyles of the femur and tibia with the patella anteriorly
  • Consists of 3 articulations:
  • Two tibiofemoral (with intervening menisci)
  • Patellofemoral 
  • Functionally flexion/extension but also allows small amount of rotation, particularly when knee is flexed, and the foot is off the ground
  • Tibiofemoral angle of 175 degree
• bones involved

  Femur

  • Two articulating surfaces with tibia separated by the intercondylar notch
  • Surface articulating the patella forms a groove

  Tibia

  • Two articular surfaces separated by intercondylar eminence
  • Medial surface is larger, oval and slightly concave
  • Lateral surface is smaller, rounder and slightly concave
• movement available

  Flexion 

  • 120 degrees with hip extension 
  • 140 degrees with hip flexion
  • 160 degrees passively

  Extension

  • 0 degrees
  • 5-10 degrees passively

  Rotation 

  • Conjunct and adjunct
• patella

  • Two surfaces separated by a ridge 
  • Medial surface is smaller and lateral surface is larger
  • Cartilage on the posterior surface is very thick to resist the stresses imposed during gait
  • The patellar retinaculum is an important stabilizer of the PFJ
• menisci

  • Semi-luner (half moon) dense fibro-cartilage
  • Function 
  • Increase congurence between the articular surfaces of the femur and tibia
  • To participate in weight bearing across the joint
  • To act as shock absorbers
  • To aid lubrication
  • To participate in locking mechanism
  • The medial meniscus is anchored to the MCL
• capsule, synovial membrane

  • Capsule – very strong, attached to the margins of the articulating bone surfaces except anteriorly (patella)
  • Reinforced by muscle tendons
  • Synovial membrane – lines the capsule but reflects into the intercondylar eminence
  • Bursae - numerous around the knee
• fat pad

  • The infrapatellar fat pad is also known as Hoffa’s fat pad
  • It is intracapsular and is well vascularized and innervated
• ligaments

  • Medial collateral
  • Lateral collateral
  • Anterior cruciate
  • Posterior cruciate
  • Oblique popliteal (expansion of the semimembranosus tendon)
  • Arcuate popliteal (strengthens lower lateral part of the capsule)
• collateral ligaments

  • MCL is a strong flat band extending from the medial epicondyle of the femur passing downwards and slightly forwards to attach to the medial condyle and shaft of the tibia, 8-9cms long
  • LCL is a rounded cord, attached to the lateral epicondyle of the femur and passes down to attach to the lateral surface of the head of the fibula, splitting the tendon of biceps femoris, 5cms long
• cruciate ligaments

  • Prevent forwards and backwards displacement of the tibia
  • ACL is in two parts – anteromedial band and posterolateral band
  • Anteromedial band is tauter in flexion
  • Posterolateral band is tauter in extension
  • PCL is in two parts – anterolateral band and posteromedial band
  • Appear crossed and twisted due to their attachments
• iliotibial band (ITB)

  • Deep fascia forms a strong cylinder around the thigh
  • The medial side it is thin but on the lateral side it is extremely thick and tough
  • Composed of two distinct layers called the iliotibial tract
  • Attached to the medial and lateral condyles of the tibia, the head of the fibula and in front to the patella
• knee joint mechanism

  • As you stand up and extend the knee, the femur rotates medially on the tibia, ligaments tighten, the knee is close-packed (through shape of joint surfaces and orientation of cruciates).
  • Muscles can relax (although there is still some activity in Quadriceps and Hamstrings) – joint is still stable
  • To unlock knee – Popliteus muscle laterally rotates femur
• blood supply

  Tibial and popliteal artery give off 10 arterial branches to form the genicular anastomosis
• nerve supply

  • Inferior gluteal nerve (gluteus maximus)
  • Superior gluteal nerve (TFL)
  • Femoral nerve (sartorius, quads)
  • Obturator nerve (gracilis)
  • Sciatic nerve (hamstrings)
• common pathologies

  • Ligamentous injuries – ACL, PCL, MCL, LCL
  • Meniscus tears
  • Tendon tears – quadriceps and patellar tendon tears
  • Knee sprain and strain
  • Patellofemoral pain syndrome
  • Iliotibial band syndrome
  • Bursitis
  • Tendonitis
  • Genu valgus and genu varus
  • Knee dislocation
  • Patellar fracture
  • Osteoarthritis
  • Rheumatoid arthritis