Knee

• Tibiofemoral joint

  • Joint surface lined with hyaline cartilage and is enclosed within a single joint cavity
  • Medial and lateral condyles of the femur articulate with the tibial condyles
  • The weight bearing component of the knee joint

  
• Patellofemoral joint

  • Joint surface lined with hyaline cartilage and is enclosed within a single joint cavity
  • Anterior aspect of the distal femur articulates with the patella
  • Allows the tendon of the quadriceps femoris (knee extensor) to be inserted directly over the knee – increasing the efficiency of the muscle

  
• Medial and lateral menisci

  1. shaped fibrocartilaginous structures in the knee

  
• Functions of medial and lateral menisci

  • To deepen the articular surface of the tibia, thus increasing stability of the joint
  • To act as shock absorbers by increasing surface area to further dissipate forces
• Attachments of medial and lateral menisci

  • Attached at both ends to intercondylar area of the tibia
  • Medial meniscus is fixed to the tibial collateral ligament and joint capsule also

  
• Most commonly injured meniscus

  Medial meniscus – damage to the tibial collateral ligament usually results in a medial meniscal tear. Lateral meniscus is smaller, has no extra attachments and fairly mobile so less likely to be injured

  
• Anterior cruciate ligament

  Attaches at the anterior intercondylar region of tibia where it blends with the medial meniscus. It ascends posteriorly to attach to the femur in the intercondylar fossa. It prevents anterior dislocation of the tibia onto the femur

  
• Posterior cruciate ligament

  Attaches at the posterior intercondylar region of the tibia and ascends anteriorly to attach to the anteromedial femoral condyle. It prevents posterior dislocation of the tibia onto the femur

  
• Bursae around the knee joint

  • Suprapatellar
  • Prepatellar
  • Infrapatellar (deep and superficial)
  • Semimembranous

  
• Function of bursae

  To reduce wear and tear of the moving structures in a joint
• Infrapatellar fat pad

  • Lies under the kneecap (patella)
  • Fills the gaps between joint tissues to stabilise the patellar during exercise

  
• The knee joint

  • A synovial hinge joint
  • Complex joint = formed by more than 2 bones and has other structures other than bone e.g. articular disc
  • The biggest joint of the body
  • Femoral distal end = convex
  • Tibia proximal end = concave
  • Formed by the interaction between the distal femur and proximal tibia (known as the tibiofemoral joint)
  • The distal femur also interacts with the patella, which is the largest sesamoid bone in the body. This interaction is the patellofemoral joint
  • Whilst tibiofemoral joint is a hinge joint that flexes and extends (sagittal plane), there is often some rotatory movement of the femur on the tibia that accompanies this

  
• Femur

  • Longest bone of the body – distal end contributes to knee joint
  • Femurs articulation with femur = patellofemoral joint

  
• Tibia

  Tibial condyle = proximal part of tibia
• Fibula

  Not a contribution to knee joint – it is attached to the tibia and provides attachment for muscles and ligaments to provide dynamic/static stability for knee joint

  
• Ligaments of the knee joint

  • Provide static stability to knee joint
  • Translation = kinematics slide and glide – resists forward translation of tibia on fibula

  
• Meniscus

  • C-shaped cartilage that acts a shock absorber for the joint
  • Helps to stabilise the knee
  • Lateral = varies in size and width
  • Medial = wider than lateral
  • Medial connects to medial collateral ligament

  
• Synovial fluid

  • Sacs of synovial fluid surrounded by synovial membranes
  • Provides lubrication for walking
• Physiological movements of the knee joint

  • Flexion/extension = 0-140 active, 0-160 passive
  • Range depends on individual

  
• Posterior muscles of the knee

  • Posterior help to extend the knee
  • Popliteus unlocks the knee from flexion to standing
  • Small muscle behind knee

  
• Anterior muscles of the knee

  Anterior help to flex the knee

  
• Blood supply to the knee joint

  • Main artery = popliteal artery
  • From here is where a lot of other blood vessels form
  • All arteries form an anastomosis around the knee joint
  • This is why posterior surface of knee is a very sensitive area
  • Any gunshot to this area can lead to rapid blood loss

  
• Nerve supply to the knee joint

  • Nerve supply = tibial nerve, common peroneal, saphenous
  • Tibial nerve is continuation from sciatic nerve (Comprised of two nerves wrapped in one sheath)
  • Common peroneal on lateral side
  • Quadriceps femoris = part of L3,4,5 myotomes
  • Saphenous nerve gives cutaneous distribution to knee joint
  • L3 = main for anteriorly
  • S2 = main posteriorly

  
• Clinical relevance of the knee joint

  • OA
  • Patellofemoral pain syndrome (PFPS)
  • Collateral ligament rupture
  • Meniscal lesions
  • Fractures and dislocations