ANATOMY AND POSITIONING OF KNEE.pptx

ANATOMY AND POSITIONING OF KNEE

1. ANATOMY AND POSITIONING OF KNEE DR . NITIN WADHWANI Prof . and H.O.D department of Radio-diagnosis, DY Patil medical college, hospital & research institute Kolhapur

2. Anatomical Representation

3. Anterior View of Knee

4. Lateral View of Knee

5. Key facts about the knee joint Type Tibiofemoral joint : Synovial hinge joint; uniaxial Patellofemoral joint : Plane joint Articular surfaces Tibiofemoral joint : lateral and medial condyles of femur, tibial plateaus Patellofemoral joint : patellar surface of femur, posterior surface of patella Ligaments and Menisci Extracapsular ligaments : patellar ligament, medial and lateral patellar retinacula , tibial (medial) collateral ligament, fibular (lateral) collateral ligament, oblique popliteal ligament, arcuate popliteal ligament,  anterolateral ligament  (ALL ) Intracapsular ligaments : anterior cruciate ligament (ACL), posterior cruciate ligament (PCL), medial meniscus, lateral meniscus Innervation Femoral nerve (nerve to vastus medialis , saphenous nerve) tibial and common fibular (peroneal) nerves, posterior division of the obturator nerve Blood supply Genicular branches of lateral circumflex femoral artery, femoral artery , posterior tibial artery, anterior tibial artery and popliteal artery Movements Extension, flexion, medial rotation, lateral rotation

6. Anterior- posterior positioning ( weight bearing) Position of patient and image receptor : The patient stands with their back against the vertical Bucky or DDR receptor The knee is rotated so that the patella lies equally between the femoral condyles. The centre of the image receptor is level with the palpable upper borders of the tibial condyles. This projection is useful to demonstrate alignment of the femur and tibia in the investigation of valgus (bow-leg) or varus (knock-knee) deformity. Any such deformity will be accentuated with weight-bearing,

7. Direction and location of the X-ray beam The collimated horizontal beam is centred 1 cm below the apex of the patella through the joint space, with the central ray at 90° to the long axis of the tibia (midway between the palpable upper borders of the tibial condyles). Frequently, both knees are requested for comparison

8. Essential image characteristics: The patella must be centralised over the femur. The image should include the proximal 1/3 of the tibia and fibula and distal 1/3 of the femur . To enable correct assessment of the joint space, the central ray must be at 90° to the long axis of the tibia and, if necessary, angled slightly cranially. If the central ray is not perpendicular to the long axis of the tibia, then the anterior and posterior margins of the tibial plateau will be separated widely and assessment of the true width of the joint space will be difficult.

9. Antero-posterior – supine Position of patient and image receptor The patient is either supine or seated on the X-ray table or trolley, with both legs extended. The affected limb is rotated to centralize the patella between the femoral condyles, and sandbags are placed against the ankle to help maintain this position. The image receptor, should be in close contact with the posterior aspect of the knee joint, with its center level with the upper borders of the tibial condyles.

10. Direction and location of the X-ray beam The vertical collimated central beam is centred 1 cm below the apex of the patella through the joint space, with the central ray at 90° to the long axis of the tibia (midway between the palpable upper borders of the tibial condyles).

11. Lateral (Basic) (turned/rolled) Position of patient and image receptor •The patient lies on the side to be examined, with the knee flexed at 45° or 90 °. The other limb is brought forward in front of the one being examined. A pad is placed under the ankle of the affected side to bring the long axis of the tibia parallel to the image receptor. The position of the limb is now adjusted to ensure that the femoral condyles are superimposed vertically. The medial tibial condyle is placed level with the centre of the receptor. An alternative method is to keep the unaffected limb behind the knee being examined with the ankle flexed and the heel resting on the lower shaft of the unaffected leg.

12. Direction and location of the X-ray beam The collimated vertical beam is centered to the middle of the superior border of the medial tibial condyle, with the central ray at 90° to the long axis of the tibia.

13. A small cranial tube angulation of 5–7° can help super-impose the femoral condyles. If over-rotated, the medial femoral condyle is projected in front of the lateral condyle and the proximal tibio -fibular joint will be well-demonstrated. If under-rotated, the medial femoral condyle is projected behind the lateral condyle and the head of the fibula is superimposed on the tibia. If the central ray is not at 90° to the long axis of the tibia, the femoral condyles will not be superimposed . Flexion of the knee at 90° is the most easily reproducible angle and allows assessment of any degree of patella alta or patella baja

14. Lateral – horizontal beam (trauma) P osition of patient and image receptor The patient remains on the trolley/bed, with the limb gently raised and supported on pads. The imaging receptor is supported vertically against the medial aspect of the knee. The center of the receptor is level with the upper border of the tibial condyle. Direction and location of the X-ray beam The collimated horizontal beam is centered to the upper border of the lateral tibial condyle, at 90° to the long axis of the tibia.

15. Antero-posterior – stress Stress projections of the knee joint are taken to show subluxa-tion due to rupture of the collateral ligaments. Position of patient and image receptor The patient and receptor are positioned for the routine antero-posterior (AP) projection. The doctor forcibly abducts or adducts the knee, without rotating the leg. Direction and location of the X-ray beam The collimated vertical beam is centred midway between the upper borders of the tibial condyles, with the central ray at 90° to the long axis of the tibia. Essential image characteristics The image should demonstrate the joint space clearly and the amount of any widening of the joint if present

16. Patella ( postero -anterior, PA) Position of patient and image receptor The patient lies prone on the table, with the knee slightly flexed. Foam pads are placed under the ankle and thigh for support. The limb is rotated to centralize the patella. The center of the receptor is level with the crease of the knee.

17. The patella may be demonstrated more clearly as it is now adjacent to the image receptor. Subtle abnormalities may not be detected, as the trabecular pattern of the femur will still predominate. This projection depends on the fitness of the patient

18. Skyline projections The skyline projection can be used to: Assess the retro-patellar joint space for degenerative disease. Determine the degree of any lateral subluxation of the patella with ligament laxity. Diagnose chondromalacia patellae. Confirm the presence of a vertical patella fracture in acute trauma. The optimum retro-patellar joint spacing occurs when the knee is flexed approximately 30–45°. Further flexion pulls the patella into the intercondylar notch, reducing the joint spacing. The patella moves a distance of 2 cm from full extension to full flexion. There are three methods of achieving the skyline projection: Supero -inferior. Conventional infero -superior. Infero -superior – patient prone.

19. 1.Supero-inferior Position of patient and image receptor The patient sits on the X-ray table, with the affected knee flexed over the side. Ideally, the leg should be flexed to 45°. T oo much flexion reduces the retro-patellar spacing. The receptor is supported horizontally on a stool at the level of the inferior tibial tuberosity border. Direction and location of the X-ray beam The collimated vertical central beam is centered over the posterior aspect of the proximal border of the patella. The central ray should be parallel to the long axis of the patella. The beam is collimated to the patella and femoral condyles. Essential image characteristics The retro-patellar space should be clearly seen without superimposition of the femur or tibia within the patella-femoral joint.

20. 2. Infero -superior Position of patient and image receptor The patient sits on the X-ray table, with the knee flexed 30–45° and supported on a pad placed below the knee. The image receptor is held by the patient against the anterior distal femur and supported using a non-opaque pad, which rests on the anterior aspect of the thigh. Direction and location of the X-ray beam The X-ray tube is lowered into the horizontal orientation. Avoiding the feet, the central ray is directed cranially to pass through the apex of the patella parallel to the long axis. The beam should be closely collimated to the patella and femoral condyles to limit scattered radiation to the trunk and head.

21. Not enough flexion will cause the tibial tuberosity to over-shadow the retro-patellar joint. Too much flexion will cause the patella to track over the lateral femoral condyle.

22. 3. Patella – infero -superior (patient prone) Position of patient and image receptor The patient lies prone on the X-ray table, with the image receptor placed under the knee joint and the knee flexed through 90°. A bandage placed around the ankle and either tethered to a vertical support or held by the patient may prevent unnecessary movement. The patient flexes the knee a further 5°, to remove any chance of superimposition of the tibia or foot on the patella-femoral joint space.

23. Direction and location of the X-ray beam The collimated vertical beam is centred behind the patella, with the vertical central ray angled approximately 15° towards the knee, avoiding the toes. Essential image characteristics The patella-femoral joint space should be clearly seen

24. Postero -anterior oblique Position of patient and image receptor The patient lies prone on the X-ray table. The trunk is then rotated onto each side in turn to bring either the medial or the lateral aspect of the knee at an angle of approximately 45° to the image receptor. The knee is then flexed slightly. A sandbag is placed under the ankle for support. The centre of the image receptor is level with the upper-most tibial condyle. Direction and location of the X-ray beam The collimated vertical beam is centred to the uppermost tibial condyle.

25. Antero-posterior oblique Position of patient and image receptor The patient lies supine on the X-ray table. The trunk is then rotated to allow rotation of the affected limb either medially or laterally through 45 °. The knee is flexed slightly. A sandbag is placed under the ankle for support. The centre of the image receptor is level with the upper border of the uppermost tibial condyle. Direction and location of the X-ray beam The collimated vertical beam is centred to the middle of the uppermost tibial condyle.

26. I ntercondylar notch (tunnel) – antero-posterior This projection is taken to demonstrate loose bodies within the knee joint. Position of patient and image receptor The patient is either supine or seated on the X-ray table, with the affected knee flexed to approximately 60°. A suitable pad is placed under the knee to help maintain the position. The limb is rotated to centralize the patella over the femur. The image receptor is placed on top of the pad as close as possible to the posterior aspect of the knee and displaced towards the femur.

27. Direction and location of the X-ray beam The collimated beam is centered immediately below the apex of the patella, with the following tube angulations to demonstrate either the anterior or posterior aspects of the notch

28. Essential image characteristics The lower femur and upper tibia are demonstrated, with the intercondylar notch clearly seen. Commonly only the 90° angulation is used. This projection may be requested occasionally to demonstrate a fracture of the tibial spines, where cruciate ligaments are attached.

29. Intercondylar notch (tunnel) – posterior–anterior (‘racing start’) The advantage of this method is the reduction in magnification and increased resolution. Position of patient and image receptor The patient is placed prone on the X-ray table and sits up onto their knees with hands forwards supporting their weight (i.e. patient is ‘on all fours’). The affected lower leg is extended with the tibia parallel to the tabletop and the patient is asked to lean forwards, moving the femur into an angle of 50° from the tabletop. (The angle formed behind the knee joint between the inner thigh and lower leg is 130°.) The unaffected knee is moved anteriorly, thus supporting the patient. The patient is asked to support body weight on unaffected knee. The position of the patient now simulates that of a sprinter ready to start a race. The receptor is placed directly against the anterior aspect of the knee joint.

30. Direction and location of the X-ray beam The collimated vertical beam is centred to the middle of the knee joint/popliteal fossa (approximately over the skin crease posterior to the joint). Essential image characteristics The lower femur and upper tibia are demonstrated, with the intercondylar notch clearly seen. Note : This method is only suitable for fairly fit patients who are able to climb onto the table and hold the position safely.

31. Thank you