Lateral knee radiography commonly raises a number of questions:

• is there a reliable technique for lateral knee radiography?
• how do I correct a lateral knee malposition?
• when is it malpositioned enough to warrant a repeat?
  

This page attempts to answer these and other lateral knee radiography questions

Ottawa rules

State that a knee X-ray is only required for patients with knee injuries with any of the following:

- Age 55 or over.
- Isolated tenderness of the patella (no bone tenderness of the knee other than the patella).
- Tenderness at the head of the fibula.
- Inability to flex to 90 degrees.
- Inability to weight bear both immediately and in the casualty department (ie, 4 steps – unable to transfer weight twice onto each lower limb regardless of limping).

Image Interpretation Course
by Heidi Gable DCR(R) PgCert
http://www.imageinterpretation.co.uk/knee.html

Synovial Joint

Synovium or capsule? The terms synovium and capsule do appear to get confused- they are not interchangeable. Synovial Cavity synovial cavity is deepest layer of joint capsule although synovium membrane is attached all around, above to articular margins of femur and below to articular margins of tibia, it is not everywhere coextensive with the capsule or ligament and tendons because of folds of synovial membrane, synovial cavity is not a simple, short, cylindrical cavity behind and above the patella, it is single cavity that is usually continuous above w/ suprapatellar bursa between the tendon of quads & femur; cruciate ligaments, meniscii, & infrapatellar fat pad are outside the synovial cavity; http://www.wheelessonline.com/ortho/synovium_of_the_knee Synovium is very variable but often has two layers. The outer layer, or subintima, can be of almost any type: fibrous, fatty or loosely "areolar". The inner layer, or intima, consists of a sheet of cells thinner than a piece of paper. Where the underlying subintima is loose the intima sits on a pliable membrane, giving rise to the term synovial membrane. This membrane, together with the cells of the intima, provides something like an inner tube, sealing the synovial fluid from the surrounding tissue (effectively stopping the joints being squeezed dry when subject to impact, such as running). The intimal cells are of two types, fibroblasts and macrophages, both of which are different in certain respects from similar cells in other tissues. * The fibroblasts manufacture a long chain sugar polymer called hyaluronan which makes the synovial fluid "ropy" like egg-white, together with a molecule called lubricin, which lubricates the joint surfaces. The water of synovial fluid is not secreted as such, but is effectively trapped in the joint space by the hyaluronan. * The macrophages are responsible for the removal of undesirable substances from the synovial fluid. http://en.wikipedia.org/wiki/Synovial_membrane The Articular Capsule of the Knee The fibrous capsule is strong, especially where local thickenings of it form ligaments. Superiorly, the fibrous capsule is attached to the femur, just proximal to the articular margins of the condyles and to the intercondylar line posteriorly. It is deficient on the lateral condyle, which allows the tendon of the popliteus muscle to pass out of the joint and insert into the tibia. Inferiorly the fibrous capsule is attached to the articular margin of the tibia, except where the tendon of the popliteus muscle crosses the bone. Here the fibrous capsule is prolonged inferolaterally over the popliteus to the head of the fibula, forming the arcuate popliteal ligament. The fibrous capsule is supplemented and strengthened by five intrinsic ligaments; patellar ligament, fibular collateral ligament, tibial collateral ligament, oblique popliteal ligament, and arcuate popliteal ligament. These are often called the external ligaments to differentiate them from the internal ligaments (e.g., the cruciate ligaments, which are internal to the fibrous capsule). http://download.videohelp.com/vitualis/med/kneejnt.htm

The knee is generally considered to be in a true lateral position when the posterior aspects of the femoral condyles are superimposed. (it is unclear why this criteria was chosen when the anterior aspects, and in particular the patello-femoral joint, are arguably of greater interest) In addition, the following are considered desirable demonstration of the patello-femoral joint demonstration of the joint space between the femoral condyles and the tibia knee flexion no greater than 30 degrees

It is difficult to establish performance criteria in plain film radiography- at best, guidelines can be useful but may do harm in that they suggest that judgement is not required. In most areas of plain film radiography, the decision to repeat should be based on a balanced judgement taking into consideration the likelihood of diagnostic yield vs the cost.

The diagnostic yield refers to the potential for additional useful diagnostic information.

The cost is in terms of:

• patient care considerations (is the patient in pain, distressed, 'at the end of their tether' etc)
• radiation dose
• money (materials, wages)
  
• opportunity cost (this cost is the forgone opportunity to provide a radiographic service to a patient who actually needed it)

This is sometimes a difficult judgement and becomes easier with experience. One thing is clear, the repeat view should be undertaken following consideration of the benefit to the patient not the radiographer. That is to say, the radiographer's reputation is not a consideration. Another way of looking at the dilemma is to "do what you can justify" on all occasions. This means that when you are taken to task over a perceived failure to repeat a particular projection, you should have a reasoned explanation.

Despite my assertion that the individual circumstances of the case need to be taken into account, the following is a consideration of when to repeat in cases of varying degrees of malposition

	This is a malpositioned lateral knee. The knee is too internally rotated. The degree of separation of the femoral condyles is so great as to warrant a repeat in most cases. Note fibula head position (black arrow) and adductor tubercle (white arrow)
	This is a less straightforward case. The knee is malpositioned. The position of the head of fibula suggests that the knee is excessively internally rotated. It could be argued that a lipohaemathrosis has been demonstrated and that a repeat will probably provide no new information. My concern would be that the fracture is not demonstrated and there is a chance that the malposition is the cause. In addition, this may be a surgical case, and the surgeon may require a well positioned lateral knee for surgical planning. On balance, I would probably repeat this projection.
	This knee is minimally malpositioned. The knee is excessively externally rotated and, in addition, tube angulation adjustment is required. A lipohaemarthrosis is demonstrated. I would not normally repeat this projection on two grounds the malpositon is minimal the repeat position requires such small adjustments in tube angle and knee rotation that it may fail to provide an improved outcome a repeat is unlikely to provide new useful diagnostic information My focus at this point would not be to produce a perfect set of knee images. Rather, I would pursue the cause of the lipohaemathrosis and I would have a very low threshold for performing oblique projections of the knee if the fracture was not demonstrated on the routine projections.
	This is a well positioned lateral knee although the knee flexion is greater than the recommended 30 degrees..

1. Fibula head Position

This patient was positioned in a 'rolled lateral knee' position. The knee is clearly not in a true lateral position. If this lateral knee was considered worthy of repeat, how would you correct the malposition? 1. Fibula head Position This is the easy one. The fibula head is projected completely clear of the tibial metaphysis. This suggests that the malposition is due to excessive external rotation of the knee. patellar fracture noted

2. The lateral femoral notch

2. The lateral femoral notch The lateral condylopatellar sulcus(arrowed) , also known as the lateral femoral notch, distinguishes the lateral femoral condyle from the medial femoral condyle. The lateral condylopatellar sulcus, also known as the lateral femoral notch, normally forms a shallow groove in the middle of the lateral femoral condyle. It represents the junction zone on the lateral femoral condyle where the tibiofemoral and patellofemoral radii of curvature meet. ... This appearance of the lateral sulcus also facilitates distinction between the lateral femoral condyle and the overlapping medial femoral condyle on the lateral projection. Duke G. Pao, MD The Lateral Femoral Notch Sign June 2001 Radiology, 219, 800-801. http://radiology.rsna.org/content/219/3/800.full

The repeat lateral knee image is shown left. The radiographer has reduced the degree of external rotation of the leg resulting in an improved lateral knee position. The lateral femoral notch is arrowed. Note that the fibula head is now largely superimposed over the tibial metaphysis.

3. The Adductor Tubercle (medial condyle)

adapted from http://www.nlm.nih.gov/visibleproofs/media/detailed/ii_a_116a.jpg	If you can imagine that you are looking at the back of your patient's left knee, this is what the distal femur would look like (may not be fractured like this though!). The smoothly surfaced adductor tubercle is on the medial side just proximal to the posterior aspect of the medial femoral condyle. This bony prominence can sometimes be utilised to differentiate the medial femoral condyle from the lateral femoral condyle when attempting to assess a malpositioned lateral knee image.
	The most reliable method for identifying the medial condyle is to locate the rounded bony tubercle known as the adductor tubercle. Kathy McQuillen-Martensen Radiographic image analysis (2nd ed) Kathy McQuillen-Martensen Elsevier Health Sciences, 2006, p319 This lateral knee is malpositioned. The demonstration of the adductor tubercle (white arrow) allows differentiation of the medial femoral condyle from the lateral femoral condyle. The fibula head is excessively superimposed over the tibial metaphysis. These two observations suggest that the knee is too internally rotated. The radiographer repeated the lateral projection with the knee in a more externally rotated position (see below left).
	The repeat lateral knee shows good superimposition of the posterior aspects of the femoral condylar articular surfaces. Note improved demonstration of the suprapatellar pouch extensive degenerative disease of the knee joint and the patello-femoral joint fabella

adapted from http://imaging.ubmmedica.com/shared/zone5/0806JMMAPPF1.JPG

Kathy McQuillen-Martensen Radiographic image analysis (2nd ed) Kathy McQuillen-Martensen Elsevier Health Sciences, 2006, p319

The Effect of Knee Flexion on the Patella and Suprapatellar Pouch adapted from http://upload.wikimedia.org/wikipedia/commons/f/f3/Knee-unfolding-recess-diagram.svg

The knee should be flexed no more that 30 degrees when performing lateral knee radiography. Flexion of the knee greater than 30 degrees tends to force the patella down into the trochlear groove of the femur and can distort/compress the suprapatellar pouch and its adjacent soft tissue structures.

Horizontal Ray

The horizontal ray is the technique of choice in trauma knee radiography. This technique has two important advantages in the patient with an acute injury the technique requires minimal movement of the patient's injured knee a lipohaemarthrosis can be demonstrated

Rolled Lateral

Rolled Lateral with Unaffected Leg Over (Rolled technique 1)	Rolled Lateral with Unaffected Leg Behind (Rolled technique 2)
Source: Jamie Beck and Gary Culpan Synergy, July 2006, p21	Source: Jamie Beck and Gary Culpan Synergy, July 2006, p22
This technique requires a small positioning sponge (or similar) to be placed under the foot on the affected side to bring the tibia parallel to the table top. My experience with this position is the the patient's knee will not automatically fall into the true lateral position. I unusually place my hand on the patient's raised hip ad roll the patient's pelvis until I am convinced that the patient's knee is in a true lateral position. Note that it is the patient's raised hip position that tends to determine the degree of knee roll.	This technique requires the foot of the affected leg to be raised and supported on the foot of the non-affected leg.

Which Rolled Lateral Knee Radiography Technique is Superior?

The superior technique is the one that works for you. Research published in Synergy in 2006 (Symes, E. Lateral Knee Radiographs: Investigating the Techniques, Synergy, July 2006, p18) reported that 43% of the radiographers preferred technique 1 and 57 % preferred technique 2 (to the authors and my surprise!). The research also reported that radiographers did not always know why a lateral knee position failed (and presumably therefore did not know how to correct the malposition).

The Indicators The lateral femoral notch is demonstrated (white arrow) The adductor tubercle is not demonstrated The fibula head position is unremarkable For Horizontal Ray Lateral Technique To Correct Rotation Error: Rotate leg internally (note insignificant error) To Correct Angulation Error: More caudal angulation For Rolled Lateral technique To Correct Rotation Error: Rotate leg internally To Correct Angulation Error: More cephalic Angulation Note: Horizontal ray technique will always require opposite angulation correction to rolled technique because one technique is a medial-lateral beam and the other is lateral-medial beam These images are presented for the purposes of demonstration and are not necessarily worthy of repeating. The decision to repeat should be based on a balanced consideration of the costs vs the likely benefits to the patient Discussion This lateral knee would not be worthy of repeating under normal circumstances There is a multilayered lipohaemarthrosis indicating articular fracture

The Indicators The lateral femoral notch is demonstrated (white arrow) The adductor tubercle is not demonstrated The fibula head is probably excessively superimposed over the tibial metaphysis For Horizontal Ray Lateral Technique To Correct Rotation Error: Rotate leg externally To Correct Angulation Error: More caudal angulation For Rolled Lateral technique To Correct Rotation Error: Rotate leg externally To Correct Angulation Error: More cephalic Angulation Note: Horizontal ray technique will always require opposite angulation correction to rolled technique because one technique is a medial-lateral beam and the other is lateral-medial beam These images are presented for the purposes of demonstration and are not necessarily worthy of repeating. The decision to repeat should be based on a balanced consideration of the costs vs the likely benefits to the patient Discusion This degree of rotation may be worthy of repeat. However, the lipohaemartrosis has been demonstrated and, if a fracture had not been demonstrated, oblique views of the knee would arguably provide a better diagnostic yield

The Indicators The lateral femoral notch is demonstrated (white arrow) The adductor tubercle is not well demonstrated (although probably visible) The fibula head is not superimposed over the tibial metaphysis suggesting excessive external rotation of the knee. For Horizontal Ray Lateral Technique To Correct Rotation Error: Rotate leg internally To Correct Angulation Error: More cephalic angulation For Rolled Lateral technique To Correct Rotation Error: Rotate leg internally To Correct Angulation Error: More caudal Angulation Note: Horizontal ray technique will always require opposite angulation correction to rolled technique because one technique is a medial-lateral beam and the other is lateral-medial beam These images are presented for the purpose of demonstration and are not necessarily worthy of repeating. The decision to repeat should be based on a balanced consideration of the costs vs the likely benefits to the patient Discussion There is a large knee effusion evident in Hoffa's fatpad and the suprapatellar pouch There is probably a lipohaemarthrosis

The Indicators The lateral femoral notch is demonstrated (white arrow) The adductor tubercle is not well demonstrated (although probably visible) The fibula position suggests too much external rotation For Horizontal Ray Lateral Technique To Correct Rotation Error: Rotate leg internally To Correct Angulation Error: More cephalic angulation For Rolled Lateral technique To Correct Rotation Error: Rotate leg internally To Correct Angulation Error: More caudal Angulation Note Horizontal ray technique will always require opposite angulation correction to rolled technique because one technique is a medial-lateral beam and the other is lateral-medial beam These images are presented for the purpose of demonstration and are not necessarily worthy of repeating. The decision to repeat should be based on a balanced consideration of the costs vs the likely benefits to the patient Discussion There is a large knee effusion evident in Hoffa's fatpad and the suprapatellar pouch There is a lipohaemarthrosis The lateral condylar sulcus is largely obscured by the overlying medial condylar articular cortcal bone

The Indicators The lateral femoral notch is demonstrated (top white arrow) The adductor tubercle is demonstrated (bottom white arrow) The fibula head appears to be excessively overlapping the proximal tibial metaphysis For Horizontal Ray Lateral Technique To Correct Rotation Error: Rotate leg externally To Correct Angulation Error: More cephalic angulation For Rolled Lateral technique To Correct Rotation Error: Rotate leg externally To Correct Angulation Error: More caudal Angulation Note: Horizontal ray technique will always require opposite angulation correction to rolled technique because one technique is a medial-lateral beam and the other is lateral-medial beam These images are presented for the purpose of demonstration and are not necessarily worthy of repeating. The decision to repeat should be based on a balanced consideration of the costs vs the likely benefits to the patient

The Indicators The lateral femoral notch is not demonstrated The adductor tubercle is not demonstrated The fibula head is largely projected free of the proximal tibial metaphysis suggesting excessive external rotation of the knee. For Horizontal Ray Lateral Technique To Correct Rotation Error: Rotate leg internally To Correct Angulation Error: More cephalic angulation For Rolled Lateral technique To Correct Rotation Error: Rotate leg internally To Correct Angulation Error: More caudal Angulation Note: Horizontal ray technique will always require opposite angulation correction to rolled technique because one technique is a medial-lateral beam and the other is lateral-medial beam These images are presented for the purpose of demonstration and are not necessarily worthy of repeating. The decision to repeat should be based on a balanced consideration of the costs vs the likely benefits to the patient Discussion This is a repeat of the lateral knee shown above. The radiographer has over-corrected the malposition error shown above. The radiographer has attempted to correct the rotation error only - the tube angle error is unchanged.

The Indicators The lateral femoral notch is demonstrated (top white arrow) The adductor tubercle is demonstrated (bottom white arrow) The head of fibula is too superimposed over the proximal tibial metaphysis suggesting the need for further external rotation For Horizontal Ray Lateral Technique To Correct Rotation Error: Rotate leg externally To Correct Angulation Error: More cephalic angulation For Rolled Lateral technique To Correct Rotation Error: Rotate leg externally To Correct Angulation Error: More caudal Angulation Note: Horizontal ray technique will always require opposite angulation correction to rolled technique because one technique is a medial-lateral beam and the other is lateral-medial beam These images are presented for the purpose of demonstration and are not necessarily worthy of repeating. The decision to repeat should be based on a balanced consideration of the costs vs the likely benefits to the patient Discussion This lateral knee position would generally be considered within acceptable positioning limits

The Indicators The lateral femoral notch is demonstrated (white arrow) The adductor tubercle is not demonstrated The fibula head position is normal For Horizontal Ray Lateral Technique To Correct Rotation Error: no change required To Correct Angulation Error: More caudal angulation For Rolled Lateral technique To Correct Rotation Error: no change required To Correct Angulation Error: More cephalic Angulation Note: Horizontal ray technique will always require opposite angulation correction to rolled technique because one technique is a medial-lateral beam and the other is lateral-medial beam These images are presented for the purpose of demonstration and are not necessarily worthy of repeating. The decision to repeat should be based on a balanced consideration of the costs vs the likely benefits to the patient

The Indicators The lateral femoral notch is demonstrated (white arrow) The adductor tubercle is not demonstrated The fibula head is largely unobscured by the proximal tibial metaphysis suggesting excessive external rotation of the knee For Horizontal Ray Lateral Technique To Correct Rotation Error: Rotate leg internally To Correct Angulation Error: no change required For Rolled Lateral technique To Correct Rotation Error: Rotate leg internally To Correct Angulation Error: no change required Note: Horizontal ray technique will always require opposite angulation correction to rolled technique because one technique is a medial-lateral beam and the other is lateral-medial beam These images are presented for the purpose of demonstration and are not necessarily worthy of repeating. The decision to repeat should be based on a balanced consideration of the costs vs the likely benefits to the patient Discussion this lateral knee position is acceptable and would not need repeating under normal circumstances.

The Indicators The lateral femoral notch is demonstrated (white arrow) The adductor tubercle is demonstrated (black arrow) The fibula head is largely overlying the proximal tibial metaphysis suggesting excessive internal rotation positioning error. For Horizontal Ray Lateral Technique To Correct Rotation Error: Rotate leg externally To Correct Angulation Error: More caudal angulation For Rolled Lateral technique To Correct Rotation Error: Rotate leg externally To Correct Angulation Error: More cephalic Angulation Note: Horizontal ray technique will always require opposite angulation correction to rolled technique because one technique is a medial-lateral beam and the other is lateral-medial beam These images are presented for the purpose of demonstration and are not necessarily worthy of repeating. The decision to repeat should be based on a balanced consideration of the costs vs the likely benefits to the patient patellar fracture noted

The Indicators The lateral femoral notch is not demonstrated The adductor tubercle is not demonstrated The fibula head position is unremarkable For Horizontal Ray Lateral Technique To Correct Rotation Error: no change required To Correct Angulation Error: ? For Rolled Lateral technique To Correct Rotation Error: no change required To Correct Angulation Error: ? Note Horizontal ray technique will always require opposite angulation correction to rolled technique because one technique is a medial-lateral beam and the other is lateral-medial beam These images are presented for the purpose of demonstration and are not necessarily worthy of repeating. The decision to repeat should be based on a balanced consideration of the costs vs the likely benefits to the patient Comment You will sometimes see a lateral knee where all of the malposition indicators are absent knee joint effusion noted ? lipohaemarthrosis

The Indicators The lateral femoral notch is demonstrated (white arrow) The adductor tubercle is demonstrated (black arrow) The fibula head position is unremarkable For Horizontal Ray Lateral Technique To Correct Rotation Error: there is insignificant error To Correct Angulation Error: More cephalic angulation For Rolled Lateral technique To Correct Rotation Error: there is insignificant error To Correct Angulation Error: More caudal angulation Note Horizontal ray technique will always require opposite angulation correction to rolled technique because one technique is a medial-lateral beam and the other is lateral-medial beam These images are presented for the purpose of demonstration and are not necessarily worthy of repeating. The decision to repeat should be based on a balanced consideration of the costs vs the likely benefits to the patient

The Indicators The lateral femoral notch is not well demonstrated (although probably visible) The adductor tubercle is not demonstrated The fibula head position is normal For Horizontal Ray Lateral Technique To Correct Rotation Error: none To Correct Angulation Error: none For Rolled Lateral technique To Correct Rotation Error: none To Correct Angulation Error: none Note Horizontal ray technique will always require opposite angulation correction to rolled technique because one technique is a medial-lateral beam and the other is lateral-medial beam These images are presented for the purpose of demonstration and are not necessary worthy of repeating. The decision to repeat should be based on a balanced consideration of the costs vs the likely benefits to the patient

The Indicators The lateral femoral notch is poorly demonstrated (top black arrow) The adductor tubercle is also poorly demonstrated (bottom black arrow) For Horizontal Ray Lateral Technique To Correct Rotation Error: insignificant error To Correct Angulation Error: increased caudal angulation For Rolled Lateral technique To Correct Rotation Error: insignificant error To Correct Angulation Error: decreased caudal angulation Note Horizontal ray technique will always require opposite angulation correction to rolled technique because one technique is a medial-lateral beam and the other is lateral-medial beam These images are presented for the purpose of demonstration and are not necessarily worthy of repeating. The decision to repeat should be based on a balanced consideration of the costs vs the likely benefits to the patient Discussion knee joint effusion noted

The Indicators The lateral femoral notch is not demonstrated The adductor tubercle is not well demonstrated The fibula head position is unremarkable For Horizontal Ray Lateral Technique To Correct Rotation Error: none To Correct Angulation Error: none For Rolled Lateral technique To Correct Rotation Error: none To Correct Angulation Error: none Note Horizontal ray technique will always require opposite angulation correction to rolled technique because one technique is a medial-lateral beam and the other is lateral-medial beam These images are presented for the purpose of demonstration and are not necessary worthy of repeating. The decision to repeat should be based on a balanced consideration of the costs vs the likely benefits to the patient Discussion large knee joint effusion noted

The Indicators The lateral femoral notch is demonstrated (white arrow) The adductor tubercle is not demonstrated The fibula head position is normal For Horizontal Ray Lateral Technique To Correct Rotation Error: none To Correct Angulation Error: none For Rolled Lateral technique To Correct Rotation Error: none To Correct Angulation Error: none Note Horizontal ray technique will always require opposite angulation correction to rolled technique because one technique is a medial-lateral beam and the other is lateral-medial beam These images are presented for the purpose of demonstration and are not necessarily worthy of repeating. The decision to repeat should be based on a balanced consideration of the costs vs the likely benefits to the patient Discussion knee joint effusion noted

The Indicators The lateral femoral notch is poorly demonstrated (white arrow) The adductor tubercle is also somewhat poorly demonstrated (black arrow) The fibula head position is normal For Horizontal Ray Lateral Technique To Correct Rotation Error: none To Correct Angulation Error: More caudal angulation For Rolled Lateral technique To Correct Rotation Error: none To Correct Angulation Error: More cephalic Angulation Note Horizontal ray technique will always require opposite angulation correction to rolled technique because one technique is a medial-lateral beam and the other is lateral-medial beam These images are presented for the purpose of demonstration and are not necessarily worthy of repeating. The decision to repeat should be based on a balanced consideration of the costs vs the likely benefits to the patient Discussion Fractured patella noted

This 73 year old lady presented with right knee pain and a history of gout. She was referred for radiography of both knees. You can be confident that you have mastered lateral knee radiography when you are producing good quality images... you can be very confident when you produce bilateral knee images that look like mirror images!

Lateral knee radiography is one of the more difficult radiographic positioning challenges (perhaps surpassed only by the lateral elbow). Persistence and practice will yield results. If you have any technique tips, you can post them as a thread on this page.