Anatomy of the Knee

Anatomy of the Knee

• Medial and lateral femoral condyles (medial larger than lateral)
• Tibial plateaus
• Intercondylar eminences or spines
• Medial and lateral tibial condyles
• Femur
• Patella
• Tibia
• Fibula

Joints of the Knee

• Patellofemoral joint
• Proximal Tibiofibular joint
• Medial and Lateral Femorotibial joints

Ligaments of the Knee

• Lateral and Medial Collateral Ligaments (LCL and MCL)
  • Strengthen the medial and lateral aspects of the joint
• Anterior Cruciate Ligament (ACL)
  • Located in the centre of the knee
  • Controls rotation and forward movement of the tibia
• Posterior Cruciate Ligament (PCL)
  • Located in the centre of the knee
  • Controls backward movement of the tibia

Knee Ossification Centers

• Patella starts to be seen on an x-ray between 2–6 years old
• Growth plates usually fuse around puberty

Knee Indications

• Trauma
• Acute Sporting Injury
• Pain
• Lumps
• Loss of Function
• Foreign Body
• Swelling
• Reduced Range of Movement (ROM)
• Infections
• Mobile Patella
• Previous Surgery

Preparing for a Knee X-Ray

• Correct Patient Identification
• Pregnancy Check (if applicable)
• Explanation of Procedure
• Remove necessary clothing, gown with opening to the back
• Patient to lay on the x-ray table
• Lead apron

Knee X-Ray Positioning

AP Knee

• X-ray: AP Knee
• kVp: 60-70kVp
• mAs: 7-10mAs
• FFD: 100-110cm
• CR: 24x30 plate
• DR: Imaging Receptor
• Cassette: Long axis of image receptor parallel with long axis of affected leg
• Centre: Centre approx.apex of patella
• Collimation: Four sides to the outer margins of the knee. Include to skin edge. Pt supine with both legs extended
• Patient Position:
  • Femoral condyles equidistant to imaging receptor
  • Leg is slightly rotated inward (internally rotate) to place knee in a true AP position

AP Weight-Bearing Knee

• Often done bilaterally. Position as per AP Knee view
• Patient needs to stand straight, knees fully extended and body weight equally distributed on the feet
• Centre between both knees
• Weight-Bearing may reveal narrowing of joint spaces that often appears normal on non-weight-bearing view
• Used for osteoarthritis, orthopaedics, pre/post op, varus/valgus deformity

AP Intercondylar Knee

• Xray: Intercondylar Knee
• kVp: 60-70kVp
• mAs: 7-10mAs
• FFD: 100-110cm
• CR: 24x30 plate
• DR: Imaging Receptor
• Cassette: Long axis of cassette perpendicular with long axis of affected leg
• Centre: CR will enter knee 1cm distal to apex of patella
• Collimation: Sufficient to include the bounds of the knee joint so soft tissue edge. Landscape rectangular shape
• Patient Position:
  • Get the imaging plate as close to the posterior side of the knee as possible- place sponges/other support needed

PA Weight-Bearing Knee Rosenberg View

• Usually done bilaterally
• Pt stands erect facing upright bucky
• Knees bent 45deg, resting knees against upright bucky
• CR- Angle the x-ray tube 10deg caudad- centre at the level of knee joint
• The Rosenberg view is more sensitive for joint space narrowing (cartilage loss) than the weightbearing AP views and is useful for the assessment of knees with early degenerative change.

Lateral Knee

• Xray: Lateral Knee
• kVp: 60-70kVp
• mAs: 7-10mAs
• FFD: 100-110cm
• CR: 24x30 plate
• DR: Imaging Receptor
• Cassette: Long axis of image receptor parallel with long axis of affected leg
• Centre: Medial aspect of knee joint
• Collimation: Four sides to the outer margins of the knee
• Patient Position:
  • Pt to roll onto affected side, to superimpose the femoral epicondyles
  • Flex knee 20-30deg
  • Place a sponge under the ankle so the long axis of the tif/fib is parallel to image receptor
  • Other leg can be either behind or in front of affected leg
  • Angle central ray 4-7deg cephalad, depending on patient presentation

Horizontal Beam Lateral Knee

• Used for acute knee injuries
• Detects lipohaemarthrosis = intra-articular fracture with escape of fat and blood from the bone marrow into the joint
• Demonstrates a fluid level in the suprapatellar pouch
• Approx. 5 degrees caudal angulation

Axial Patella / Skyline View

• Xray: Skyline Knee
• kVp: 60-70kVp
• mAs: 7-10mAs
• FFD: 100-110cm
• CR: 24x30 plate
• DR: Imaging Receptor
• Cassette: Long axis of image receptor perpendicular with long axis of affected leg
• Centre: Centre to apex of patella
• Collimation: Four sides to the outer margins of the patella and joint space
• Patient Position:
  • Pt supine with affected leg extended
  • Bend affected knee 45deg (depending on patient presentation)
  • Image receptor resting on mid-thigh and tilted so perpendicular to central ray
  • Pt can hold the image receptor in position for a supine position
  • Angle central ray so it's parallel to the patella and travelling through the joint space

Evaluation Criteria for Knee X-Rays:

AP Knee

• Regional anatomy should include distal femur and proximal tibia and fibula, including soft tissue
• Femorotibial joint space should be open
• Femoral and tibial condyles should appear symmetrical
• Patella should be superimposed on the midline of the femur
• Medial half of fibula head superimposed on tibia
• Density and contrast should be optimal to visualise bone & soft tissue

Intercondylar Knee

• Regional anatomy should include distal femur and proximal tibia and fibula, including soft tissue
• Intercondylar fossa should be open (not superimposed by apex of patella)
• Femorotibial joint space should be open
• Intercondylar eminence should be separated and in the center of the intercondylar fossa
• No rotation- Femoral and tibial condyles appear symmetrical
• Density and contrast should be optimal to visualise bone & soft tissue

Lateral Knee

• Regional anatomy should include distal femur and proximal tibia and fibula, including soft tissue
• Femoropatellar joint space should be open
• Femoral condyles should appear superimposed
• Patella in profile
• Fibular head only slightly superimposed over the tibia
• Density and contrast should be optimal to visualise bone & soft tissue

Skyline Knee

• Regional anatomy should include distal femur and patella, including soft tissue
• Base and apex of patella superimposed
• Femoropatellar joint space should be open
• Patella in profile
• Femoral condyles appear symmetrical
• Density and contrast should be optimal to visualise bone & soft tissue

Knee Pathology

• Fracture
• Peri-prosthesis fracture
• Dislocation

Osteoarthritis of the Knee

• Common protocol includes weight-bearing views
• Caused by repetitive & mechanical stresses over many decades. Often in people over 50
• Presentation includes pain, stiffness and locking joints
• Obvious visual deformity may include uneven gait and varus or valgus deformity
• Radiographic Appearance:
  • Decreased joint space
  • Joint margin osteophytes (bone spur)
  • Subchondral (bone below cartilage in a joint) bone sclerosis (pathological hardening)

Loose Bodies in the Knees

• Presentation includes pain, catching & joint locking
• Caused by trauma or degenerative disease
• Usually well demonstrated on intercondylar projection

Varus Deformity

• "Bow legged"
• Angular deformity of lower legs outwards
• Medial joint destruction
• Assessed with long leg radiographs

Valgus Deformity

• "Knock knee"
• Angular deformity of the lower legs inwards
• Lateral joint destruction
• Assessed with long leg radiographs

Total Knee Replacement (TKR)

• Replace articular surfaces of femur, tibia and patella
• Complications - instability, bone fracture, infection, loosening of prosthesis
• Key imaging principle: Always include all of hardware- including cement

Fabella

• Accessory ossicle in the gastrocnemius muscle
• Occurs in 10-30% of the population

Knee Dislocation

• Patellofemoral dislocation = patella becomes dislocated from the groove in the femur
• Patellofemoral Subluxation = due to ruptured ligament and the knee will temporarily dislocate and then relocate
• Femorotibial (rare) = femur and tibia dislocate
• Dislocations can have associated fractures

Patella Fracture

• Caused by direct force to patella or sudden forceful contraction of the quadriceps tendon
• Point tenderness, swelling, large joint effusion
• Transverse (most common), comminuted, pathological fracture

Bipartite & Tripartite Patella

• Commonly mistaken for a fracture
• Bipartite = 2 part patella
• Tripartite = 3 part patella
• Congenital condition where there is a fusion failure of the accessory ossification centre

Osgood Schlatter Disease

• Occurs in active children aged 9–16 coinciding with periods of growth.

This quiz focuses on the detailed anatomy of the knee, including its structure, joints, ligaments, and ossification centers. It covers essential aspects such as femoral condyles, tibial plateaus, and common knee injuries. Test your knowledge of knee anatomy and its implications for function and injury.