Knee Radiography Lecture Notes (PDF)

RMI 221 Radiographic Anatomy & Positioning 1 Lecture 12 Radiography of the Knee Joint fchs.ac.ae Learning Outcomes After today’s lecture you will be able to: Identify the main reasons that knee radiography is performed; List...

RMI 221 Radiographic Anatomy & Positioning 1 Lecture 12 Radiography of the Knee Joint fchs.ac.ae Learning Outcomes After today’s lecture you will be able to: Identify the main reasons that knee radiography is performed; List all of the routine or standard projections for knee radiography; Describe the positioning methods for routine projections of the knee joint. fchs.ac.ae Reading The prescribed texts relating to this lecture are: Bontrager, K.L. & Lampignano, J.P. (2010), Textbook of Radiographic Positioning and Related Anatomy, 7th edition, Mosby, St Louis, Missouri. McQuillen Martensen, K. (2011), Radiographic Image Analysis, 3rd edition, W.B. Saunders, St Louis, Missouri. The prescribed reading is: Bontrager, K. & Lampignano, J. (2010), Chapter 7, pp.214-215, 223, 242, 245, 249-251. McQuillen Martensen, K. (2011), Chapter 6, pp.354-385. Additional reading recommended for knee projections: Frank E. D., Long B. W. & Smith B. J. (2007) Merrill’s Atlas of Radiographic Positioning and Procedures 11th edition, C.V. Mosby, St Louis, Missouri, pp.302-307, 312-316. fchs.ac.ae Overview 1. Anatomical points 6. Additional projections 2. Clinical rationale 7. Supplementary projections 3. Patient preparation 8. Examples 4. Radiographic projections 9. Activity – Technique 5. Positioning of the patient – Basic/standard/routine – Special considerations fchs.ac.ae  1. Anatomical Points Bones that make up the knee joint are 4 bones: 1. femur 2. tibia. 3. fibula 4. Patella fchs.ac.ae Anatomical Points (continued) Fig 7-22, Bontrager & Lampignano (2005) Fig 7-21, Bontrager & Lampignano (2005), p.218. Distal femur and patella- Lateral view Distal femur and patella- axial view Anatomical Points (continued) The knee joint is a complex joint primarily involves two joints: – Femorotibial joint(FTJ) synovial hinge joint , and Patellofemoral joint (PFJ) modified hinge joint. Generally, the FTJ is the primarily joint, regarded as the knee joint. fchs.ac.ae  Anatomical Points (continued) Four major ligaments: Articular cartilage: Smooth cartilage allows the – Posterior cruciate bones to move easily within the joint without – Anterior cruciate friction. It covers the ends of the femur and tibia – Fibular collateral as well as the back of the patella. – Tibial collateral Meniscus: two crescent-shaped disks of cartilage. Lie between the lower end of the femur and the upper end of the tibia, and act as shock absorbers. fchs.ac.ae Anatomical Points (continued) Collateral ligaments: These ligaments are on the sides of your knee. - Tibial collateral: also known as medial collateral ligament (MCL): ligament connects your femur and tibia. - Fibular collateral: also known as lateral collateral ligament (LCL) connects the femur and fibula. These ligaments provide sideways movement of the knee. fchs.ac.ae Anatomical Points (continued) Cruciate ligaments: These ligaments are inside your knee joint. They cross each other form an “X.” These ligaments control the way your knee moves back and forth. - Anterior cruciate ligament: is in the front, controls forward movement of the tibia. - posterior cruciate ligament: is in the back, controls backward movement of the tibia. fchs.ac.ae 2. Clinical Rationale Reasons for performing knee x-rays include: Injury or trauma to: – Soft tissue Sprains, (ligament injury) Strains, (tendon injury) Tears Effusions – Bone Fractures Dislocations Disease: – Acquired – Congenital conditions fchs.ac.ae Clinical Rationale (continued) Most common soccer injury – is (MCL) medial collateral ligament injury- a blow to the medial side of the knee, cause (ligament sprain) rupture of the tibial collateral ligament. Plain film imaging still undertaken prior to MRI or arthroscopy for assessment of bony injury. Fig 7-25, Bontrager & Lampignano (2005) Fig 7-24, Bontrager & Lampignano (2005) fchs.ac.ae Clinical Rationale (continued) Internal Derangement Knee (IDK) is a term used to describe several varieties of injury to the knee joint including: – Sprains due to tearing of the capsule of the knee joint or its collateral ligaments. – Tears involving the menisci referred to as “torn cartilage” Fig 7-27, Bontrager & Lampignano (2010) fchs.ac.ae Clinical Rationale Example: Left Knee Post-Knee Reconstruction Series fchs.ac.ae Clinical Rationale (continued) In acute injury, a horizontal beam lateral is essential to detect lipohemarthrosis. - lipohemarthrosis: Blood and fat leak out of the medullary cavityin the bone, forming a fat- blood level in the suprapatellar pouch. Radiopaedia.org fchs.ac.ae Clinical Rationale (continued) lipohemarthrosis typically seen in fracture of the tibial plateau. This may be the only sign of a tibial plateau fracture on the plain films. – Nicholson & Driscoll (1995), p. 38. fchs.ac.ae Activity 1: Clinical Rationale Discussion Point What are two technical considerations that are important in order to detect lipohaemoarthrosis? 1. Horizontal beam method to establish a level. 2. Correct exposure. fchs.ac.ae  Clinical Rationale (continued) Fractures due to: 1.Trauma – direct fracture 2.Pathological – indirect fracture Types include: 1. Supracondylar fracture of the distal femur. – may also involve the knee joint. 2. Lateral tibial condyle fracture 3. Tibial plateau fracture Fig 4-96, Eisenberg & Johnson (2012) fchs.ac.ae  Clinical Rationale (continued) Isolated fracture of the proximal fibula fchs.ac.ae Clinical Rationale (continued) Miscellaneous joint disorders: 1. Osteochondritis dessicans – A joint condition in which bone underneath the cartilage of a joint dies due to lack of blood flow. This piece of bone and cartilage can then become detached from the articular cartilage. – Occurs most commonly in children and adolescents, seen most often on the lateral aspect of the medial condyle. – In the paediatric patient it is important not to confuse this with normal growth plate. To exclude osteochondritis dessicans requires: – Intercondylar fossa projection of the (knee) – Tangential, or skyline, projection of the (patella) fchs.ac.ae Clinical Rationale (continued) Can also occur in the patella: Chondromalacia patellae - Also known as runners' knee involves softening of the cartilage under the patella results in wearing away of this cartilage. fchs.ac.ae Clinical Rationale (continued) 2. Synovial chondromatosis or Synovial Osteochondromatosis - In this condition cartilaginous metaplasia takes place within the synovial membrane of the joint. Radiologically characterized by: Small numerous cartilaginous nodules that may calcify in the joints. fchs.ac.ae Clinical Rationale (continued) 3. Osgood-Schlatter’s disease - Is inflammation of the bone and cartilage of the anterior proximal tibia (at the tibial tuberosity). - Most common in boys 10 to 15 years old. fchs.ac.ae Clinical Rationale (continued) Osgood-Schlatter’s disease: Requires soft tissue lateral projection of the knee. Must be able to visualize the tibial tuberosity. The affected tubercle will appear somewhat fragmented in comparison with the normal tubercle. Ultrasound and MRI show the soft tissue (ST) component. Clinical Rationale (continued) Other indications include: Paget’s disease, exostosis, lesions and growths, including malignancy. Exostosis: a benign condition of extra growth of a bone extending outwards from the surface of the bone. fchs.ac.ae Clinical Rationale (continued) Bone tumour: Osteosarcoma most commonly happens in the long bones around the knee such as distal femur and proximal of tibia at knee joint. Osteosarcoma is the most common primary malignancy in knee. Affects the young age (10-25) years. fchs.ac.ae Clinical Rationale (continued) Osteosarcoma can appear in different ways on an X-ray, but typical findings include: "sunburst" pattern- (Sharpey's fibers stretch out perpendicular to the bone). Cloudlike appearance — a white, cloud-like lesion Sunburst appearance Sunburst pattern Cloudlike density appearance fchs.ac.ae Clinical Rationale (continued) Arthritis: Osteoarthritis (OA) Fig 4-25, Eisenberg & Johnson (2012) – Is a degenerative joint disease, non inflammatory. – characterized by: 1. Thin, and erosion cartilage. 2. Bone ends rub together. 3. Joint space narrowing is asymmetrical. – Knee is the most frequent site for OA. – Best shown in the intercondylar fossa projection. fchs.ac.ae Clinical Rationale (continued) Arthritis: Rheumatoid arthritis (RA) - is an autoimmune disease causes joint inflammation and pain. - Characterized by: 1. Swallowed inflamed synovial membrane 2. Bone erosion 3. Affects the knees on both sides equally. fchs.ac.ae Rheumatoid arthritis vs Osteoarthritis Osteoarthritis Rheumatoid arthritis fchs.ac.ae 3. Patient Preparation Patients may be in significant pain; Patients may have difficulty extending the knee for the AP projection; Many patients will need assistance to get up onto the x-ray table – consider leaving patient on the trolley; It is advisable to have patients take off trousers/slacks and put on a gown. Use gonadal shielding – Especially important with the supine patient for the intercondylar fossa projection and tangential for the patella projection; If patient is badly injured and presents with leg in an air splint, air splint must be left on. – For trauma patients use a horizontal beam for the lateral projection. fchs.ac.ae 4. Radiographic Projections Basic projections: Supplementary projections: AP AP oblique projection- medial Lateral (internal rotation) AP oblique projection- lateral Additional projections: (external rotation) Intercondylar fossa Tangential projection AP weightbearing projection of the patella PA axial weightbearing projection Stress projections fchs.ac.ae Some Technique Considerations If patient has a prosthesis or surgical implants (plates, nails, screws), the full length of the implant must be demonstrated: Minimum 24 × 30 cm IR, usually longer. Hint: Look at the surgical scar to gauge length. fchs.ac.ae Technical Factors SID 100 cm Small focal spot kVp range (60-70) Short exposure time If both knees are requested, AP view usually taken together. fchs.ac.ae Basic Radiographic Projections AP: Include distal third of femur and proximal third of tibia and fibula. Patella should be superimposed over the femur. Fig 6-70 and 6-74, McQuillen Martensen (2011) fchs.ac.ae 5. Positioning of the Patient: Standard AP Projection Patient supine, with fully extend the leg. Centre cassette to apex of patella Adjust femoral epicondyles parallel to plane of the film. Femorotibial joint space should be open. The fibula head is a great indication of rotation, if the fibula head is entirely superimposed, the image is not AP. - To correct this, you must internally rotate 3° to 5° until the knee is in even contact wit the image detector. Fig 7-102, Bontrager & Lampignano (2005) fchs.ac.ae Positioning of the Patient: Standard AP Projection Determination of CR: CR 1.25 cm distal to the apex of the patella. Very slim patients with a thin thighs require 3° to 5° caudal angle to better visualize the joint space in an AP. Larger patients with larger thighs requiring a 3° to 5° degrees cephalad angle. Fig 7-101, Bontrager & Lampignano (2005) fchs.ac.ae Basic Radiographic Projections Lateral: Knee flexed 20 -30  Include distal femur and proximal tibia and fibula. Fig 7-109, Bontrager & Lampignano (2006) Fig 6-80, McQuillen Martensen (2011) fchs.ac.ae Positioning of the Patient: Standard Lateral Projection Patient turns onto the affected side: – Mediolateral Knee flexed 20 -30 CR directed 5 -7 cephalad to a point 2.5 cm distal to the medial epicondyle. Fig 7-111, Bontrager & Lampignano (2005) Fig 6-85, McQuillen Martensen (2011), fchs.ac.ae How much Knee Flexion is Required? The knee should be flexed no more that 30 degrees when performing lateral knee radiography. Flexion of the knee greater than 30 degrees will: 1. tightness muscles and tendons that may obscure important diagnostic information in the joint space. 2. force the patella drawn into the trochlear groove of the femur, which will compress the suprapatellar pouch and its adjacent soft tissue structures. fchs.ac.ae  How much Tube Angulation is Required? Short patients with a wide pelvis a 7  to 10  cephalad angle is required. Long male patients with narrow pelvis required a very little angulation about 5 . Note: Female commonly demonstrate greater pelvic width and femoral inclination, and males demonstrate narrower pelvic width and femoral inclination, variations occur in both sexes. Each patient's pelvic width and femoral length should be evaluated to determine the degree of angulation to use. fchs.ac.ae Positioning of the Patient: Standard Lateral Projection How will you know if you have positioned the knee true lateral? “Grasp the epicondyles and adjust so that they are perpendicular to IR (condyles superimposed)” – Frank et al. (2007), p. 306. “Femoral epicondyles directly superimposed and plane of patella perpendicular to plane of IR” – Bontrager & Lampignano (2010), p. 245. fchs.ac.ae  Additional projections of the knee Intercondylar fossa projections Tangential projection of patella (Discussed next lecture) 6. Additional projections of the knee: Intercondylar fossa Projections Intercondylar fossa: Also called notch or tunnel projection Demonstrates the fossa Tibial spine Fig 6-91 and 6-93, McQuillen Martensen (2011) Articular facets of the tibial plateau The resultant radiograph must demonstrate the fossa free from any superimposition of the lower pole of the patella. fchs.ac.ae Additional projections of the knee: Intercondylar fossa Projections (continued) 1. PA axial: Holmblad Method 2. PA axial: Camp Coventry Method 3. AP axial: Beclere Method fchs.ac.ae Positioning of the Patient: Intercondylar Fossa projections PA axial: Holmblad Method Patient in kneeling position. Leg positioned to make angle between femur and cassette of 60  to 70  CR directed to midpopliteal crease. – Bontrager & Lampignano (2010), p. 249 Fig. 7-119, Bontrager & Lampignano (2010) Fig 7-115, Bontrager & Lampignano (2006) fchs.ac.ae Positioning of the Patient: Intercondylar Fossa Projection (continued) PA axial: Camp Coventry Method Patient in prone position. Flex lower leg 40° to 50°, place radiolucent support. CR angle 40° to 50° caudad to match the flexion, directed to midpopliteal crease. Fig 7-117, Bontrager & Lampignano (2010) fchs.ac.ae Positioning of the Patient: Intercondylar Fossa Projection (continued) AP axial: Beclere Method Patient in supine position. Knee flexed 40 ° to 45 °, over crosswise cassette. Place support under cassette. CR 40  to 45  cephalad, directed 1.25cm distal to apex of patella. – Bontrager & Lampignano (2010), p. 251 Fig 7-118 and 7-121, Bontrager & Lampignano (2006) fchs.ac.ae Supplementary projections of the Knee AP oblique projection- medial (internal) rotation AP oblique projection- lateral (external) rotation AP weightbearing projection PA axial weightbearing projection Stress projections Supplementary Projections of the Knee Oblique projections: Also a supplementary projections of the patella, required to show each half of the patella separated from the femur. Clinical Indications: - Fractures - Lesions - Joint space abnormalities fchs.ac.ae 7. Supplementary Projections of the Knee AP oblique- medial rotation: Patient supine, rotate entire leg internally 45°. CR to midpoint of the knee 1.25cm distal to apex of patella. Proximal tibiofibular joint open. The head and neck of fibula are visualized without superimposition. Half of the patella should be seen free of superimposition. Figs 7-102, 7-103 and 7-105, Bontrager & Lampignano (2005) Supplementary Projections of the Knee (continued) AP oblique- lateral rotation: Patient supine, rotate entire leg externally 45°. CR to midpoint of the knee 1.25cm distal to apex of patella. Proximal fibula superimposed by the proximal tibia. Half of the patella should be seen free of superimposition. Figs 7-105, 7-106 and 7-108, Bontrager & Lampignano (2005) AP Oblique views of left knee AP medial oblique AP lateral oblique Weightbearing Projections Weightbearing AP/PA projection: Bilateral knees included. For varus and valgus deformity. valgus - Valgus: is when the knees bend inward. - Varus: causes the knees to bow outward. Cassette in vertical orientation. Varus fchs.ac.ae Supplementary Projections of the Knee (continued) AP weightbearing projection: Bilateral knees included on same exposure for comparison. For assessment of joint severe OA. Possible cartilage degeneration. Fig 7-111, 7-112 ,Bontrager & Lampignano (2010) Patient erect. Position feet straight with weight evenly distributed on both feet. CR directed to midpoint between knee joints. fchs.ac.ae Supplementary Projections of the Knee (continued) PA axial weightbearing projection-Rosenberg method: Bilateral knees for compression. Femorotibial joint spaces of the knees demonstrated for possible cartilage degeneration. Patient erect. Knees in pa, flexed 45 . Fig 7-113, 7-116, Bontrager & Lampignano (2010) CR angle is 10  caudad, to midpoint between knee joints. fchs.ac.ae  Supplementary Projections of the Knee (continued) Stress projections: Demonstrate subluxation of the knee joint. – Joint stress should always be applied by the radiologist or orthopedic surgeon. Image 56, McQuillen Martensen (2011) Image 57, McQuillen Martensen (2006) fchs.ac.ae Knee Radiographic Examples 8. Example: Left Knee AP and Lateral view fchs.ac.ae Example- Left knee series Figs 7-101 and 7-109, Bontrager & Lampignano (2005) fchs.ac.ae Example: AP oblique views- patient with Osteopenia AP medial oblique AP lateral oblique Example: knee Bilateral- Patient with Osteoarthritis AP weightbearing Example: Right Knee Series- Patient with Paget’s Disease fchs.ac.ae Example: Bilateral knee weightbearing projection- Valgus deformity Activity 2: Radiographic Projections of the Knee What CR angulation is required for the PA axial weight- bearing bilateral knee projection (Rosenberg Method)? A. 5° to 7° cephalad B. 5° to 7° Caudad C. 20° to 25° cephalad D. 10° only caudad fchs.ac.ae Summary Anatomical points Patient positioning Clinical rationale Additional radiographic projections – Injury or trauma Supplementary radiographic projections Soft tissue Knee Radiographic Examples Bone Activity – Disease Acquired Congenital conditions Patient preparation Basic Radiographic projections – Technique fchs.ac.ae References Bontrager, K.L. & Lampignano, J.P. (2005), Textbook of Radiographic Positioning and Related Anatomy, 6th edition, Mosby, St Louis, Missouri. Bucholz, R.W., (2010), Rockwood and Green's Fractures in Adults, 7th edition, Wolters Kluwer Health/Lippincott Williams & Wilkins, Philadelphia. Eisenberg R.L., & Johnson, N. M. (2012), Comprehensive Radiographic Pathology, 5th edition, Mosby Elsevier, St Louis, Missouri. Nicholson, D.A. & Driscoll, P.A. (Eds.), (1995), “ABC of Emergency Radiology”, British Medical Journal. fchs.ac.ae