Normal Knee X-ray: Views, Anatomy & Radiographic Landmarks

Last Updated on October 18, 2025

The knee is one of the most frequently imaged joints in orthopedic practice. As a major load-bearing articulation of the lower limb, it is highly susceptible to trauma, degenerative change, and malalignment. A normal knee X-ray serves as the essential baseline for identifying subtle abnormalities in alignment, joint space, bone contour, and soft-tissue shadows.

Despite advances in CT and MRI, the X-ray continues to be indispensable because of its low cost, accessibility, and value for serial comparison. Interpreting knee radiographs correctly requires a precise understanding of normal osseous and soft-tissue anatomy as it appears on different views.

Routine evaluation of the knee involves anteroposterior (AP) and lateral projections that together demonstrate the femoral condyles, tibial plateaus, joint congruence, and the patellofemoral relationship.

Supplementary views, such as skyline (axial/tangential) and intercondylar (tunnel or Rosenberg) projections, are used when patellar alignment, trochlear morphology, or cruciate insertion areas need further assessment.

Weight-bearing views are crucial for assessing deformities and joint space narrowing under physiological load.

The following sections describe standard projections, radiographic landmarks, normal measurement parameters, and interpretive cues used in evaluating knee radiographs across age groups.

Anatomical Landmarks on Knee X-rays

[Read more on the anatomy of the knee]

Anteroposterior (AP) View

The AP view provides a frontal visualization of the tibiofemoral joint and adjacent structures. It allows evaluation of joint alignment, condylar morphology, and tibial plateau contour.

Key Normal Landmarks

Femoral Condyles

On a normal radiograph, both femoral condyles appear equal in width and smooth in outline. The medial condyle is slightly longer anteroposteriorly, but both should look symmetrical overall.

Any asymmetry or cortical irregularity may suggest a fracture, osteochondral defect, or erosive arthritis.

Tibial Plateaus

Normally, the tibial plateaus appear flat or slightly concave and parallel to the femoral condyles. The medial plateau lies slightly lower than the lateral one. Depression or irregularity of the plateau may indicate a tibial plateau fracture or early arthritis.

Joint Space

In a healthy knee X-ray, the joint space is uniform, about 4 to 6 mm across both the medial and lateral compartments. Narrowing of this space implies cartilage loss or meniscal deficiency.

Intercondylar Eminence (Tibial Spines)

The intercondylar eminence should be centered and equidistant between the femoral condyles. The displacement of the tibial spines may indicate cruciate ligament injury or rotational malalignment.

Fibular Head

Normally, the fibular head is partially superimposed by the lateral tibial condyle; this overlap confirms proper limb rotation during imaging. Excessive visibility or absence of overlap suggests internal or external rotation of the limb during the X-ray.

Patella

The patella should overlie the distal femur, positioned slightly lateral to the midline but not beyond the lateral condyle. Lateral displacement may point to patellar maltracking or rotational malalignment.

Soft-Tissue Shadows

Quadriceps and patellar tendon outlines are usually visible, and the suprapatellar pouch may occasionally be seen. But soft tissue shadows depend on image quality.
Effacement or increased density in the soft-tissue shadows can indicate joint effusion or hemorrhage.

Technical Tip: On a correctly positioned AP view, both femoral condyles are symmetric, the fibular head overlaps the lateral plateau by approximately one-third, and the patella lies central.

Lateral View

The lateral view depicts the sagittal relationships of the distal femur, proximal tibia, and patella, emphasizing patellofemoral congruence and posterior condylar alignment.

Key Normal Landmarks

Femoral Condyles

In a properly positioned lateral knee radiograph, the posterior aspects of the femoral condyles should be perfectly superimposed, forming a single dense cortical line. This superimposition confirms correct limb rotation and positioning.

If the condyles are not fully superimposed, it usually indicates a rotation error during imaging.

Patellofemoral Joint

The patellofemoral joint space should be clearly visible and uniform, with smooth and continuous articular surfaces on both the patella and the distal femur. Any narrowing of this space or the presence of a step deformity may suggest patellar maltracking or an underlying chondral injury.

Patella

The patella normally lies anterior to the distal femur with its apex directed inferiorly. Its height in relation to the femur and tibia can be evaluated using the Insall–Salvati ratio. A patella that appears abnormally high (patella alta) or low (patella baja) may indicate extensor mechanism imbalance or previous trauma.

Tibial Plateau

On a normal lateral view, the tibial plateau shows a slight posterior inclination of approximately 7 to 10 degrees. Any flattening or depression of this surface can point toward a tibial plateau fracture or degenerative arthritic change.

Fibular Head

The fibular head should appear slightly overlapped by the tibia, but its cortex must remain distinct and well-defined. If the fibular head projects too far anteriorly or shows excessive overlap, it typically reflects a rotational malposition during the X-ray.

Fat Pads

Both the suprapatellar and infrapatellar (Hoffa’s) fat pads appear as parallel radiolucent stripes anterior to the distal femur and tibia. Displacement or obliteration of these fat pads often indicates joint effusion or adjacent soft-tissue swelling.

How to Confirm View?
When the posterior aspects of femoral condyles are superimposed and the adductor tubercle is seen slightly proximal and posterior to the lateral condyle, the projection is considered anatomically correct.

Skyline (Axial / Tangential) View

The skyline (patellofemoral) projection profiles the relationship between the patella and trochlear groove.

Key Normal Landmarks

Patella

The patella appears as a roughly triangular bone free from superimposition, with its apex directed inferiorly and the articular surface facing posteriorly toward the femoral trochlea. The posterior surface of the patella is divided into medial and lateral facets by a faint vertical ridge.

Of these, the lateral facet is broader, flatter, and slopes more gently, while the medial facet is narrower and more steeply inclined.

Trochlear Groove

It is the curved surface of the distal femur where the patella slides. It appears as a smooth, concave depression, usually symmetrical or with a slightly larger lateral facet. The central ridge of the patella lies within the trochlear groove, and the lateral tilt should be less than 5°

Interpretation
Loss of the normal concavity of the trochlear groove, asymmetry between the facets, or excessive lateral tilt of the patella suggest patellofemoral maltracking or trochlear dysplasia. Subchondral irregularity or narrowing of the joint space may indicate chondromalacia or early patellofemoral osteoarthritis.

Indications for Knee Radiographs

Radiographic evaluation of the knee is performed for a wide spectrum of clinical indications, ranging from acute trauma to chronic degenerative disorders. Properly selecting patients for X-ray examination is critical for diagnostic efficiency and for minimizing unnecessary radiation exposure.

Common Clinical Indications

Knee radiographs are typically obtained in the following scenarios:

• Trauma: Suspected fracture, dislocation, or avulsion injury.
• Pain or swelling: Acute or chronic knee pain, unexplained effusion, or restricted motion.
• Deformity or malalignment: Assessment of varus or valgus knee, rotational malalignment, or postoperative deformity correction.
• Degenerative and inflammatory conditions: Evaluation of osteoarthritis, rheumatoid arthritis, or crystal arthropathy for joint space narrowing, osteophytes, and subchondral changes.
• Infection: Suspicion of septic arthritis or osteomyelitis (periarticular osteopenia, erosions, or periosteal reaction).
• Neoplastic and cystic lesions: Local bone pain, lytic or sclerotic changes, or palpable mass.
• Postoperative or post-procedural evaluation: Following internal fixation, arthroplasty, osteotomy, or ligament reconstruction to check hardware placement, alignment, and healing.

Ottawa Knee Rules for X-rays in Knee Injury

In the emergency setting, the Ottawa Knee Rules provide evidence-based guidance on when radiographs are necessary following acute knee injury. According to these criteria, a knee X-ray is indicated if any of the following are present:

• Patient age 55 years or older.
• Isolated tenderness of the patella (no other bony tenderness of the knee).
• Tenderness at the head of the fibula.
• Inability to flex the knee to 90°.
• Inability to bear weight both immediately after injury and for four steps in the emergency department (two steps on each leg, regardless of limping).

These rules have a high sensitivity (~98–100%) for detecting clinically significant fractures and are widely adopted to reduce unnecessary radiographs after knee trauma.
However, they do not substitute for clinical judgment, particularly in high-energy trauma, pediatric patients, or when suspicion for complex injuries (e.g., tibial plateau fracture) remains high.

Additional Considerations

Even when the Ottawa criteria are not met, radiographs may still be justified in:

• Chronic knee pain is unresponsive to conservative care.
• Pre- and post-surgical assessment of mechanical alignment.
• Weight-bearing or functional deformity evaluation in osteoarthritis or post-traumatic malunion.
• Pediatric knees with concerns about the growth plate or suspected epiphyseal injury.

Standard Radiographic Projections of the Knee

A proper understanding of standard knee radiographic views is crucial for accurate diagnosis. Each projection provides unique anatomic and biomechanical information, and a complete study typically includes anteroposterior (AP) and lateral views, with skyline, intercondylar, and weight-bearing views added as indicated.

Anteroposterior (AP) View

The AP view demonstrates the tibiofemoral joint, distal femur, proximal tibia and fibula, and patella in a frontal plane. It is the fundamental projection for evaluating bony alignment, condylar symmetry, and joint space.

AP view is the best knee view for assessing tibiofemoral alignment, plateau contour, and osteoarthritic joint space narrowing. Standing AP views are preferred for evaluating functional deformities and joint loading.

Technique:

• The patient lies supine or stands erect for a weight-bearing study.
• The leg is extended with the knee and ankle joints resting on the table or detector, ensuring neutral rotation.
• The central beam is directed vertically to a point approximately 1.5 cm distal to the apex of the patella.[The center of the knee lies there]
• Exposure is made with full extension unless flexion is specifically requested.

Cues for Normal Knee X-ray, AP view

• Femoral and tibial condyles appear symmetrical.
• Joint space is uniform, typically 4–6 mm medially and laterally.
• The fibular head is partially superimposed by the lateral tibial condyle, an indicator of correct rotation.
• The patella lies centrally over the distal femur.
• Normal trabecular continuity without cortical breaks or lytic zones.

Lateral View

The lateral projection provides a sagittal visualization of the knee joint, revealing relationships between the femoral condyles, the tibial plateau, and the patella. The lateral view is essential for evaluating the patellofemoral relationship, joint effusion, tibial slope, and posterior condylar morphology.

Techniques

Two standard methods are used:

Horizontal Beam Lateral (Cross-table Lateral)

• Ideal for acute injuries or effusion evaluation as it involves minimal patient movement
• The affected knee is flexed to approximately 30–45°.
• The beam passes horizontally, perpendicular to the long axis of the limb.
• The detector is placed against the medial aspect of the knee.
• Minimal patient movement is required, making it suitable for trauma cases.
• Useful for detecting lipohemarthrosis (fat-fluid level).

Rolled (True) Lateral View

• The patient lies on the affected side, knee flexed 20–30°.
• The opposite limb is positioned behind for balance.
• The X-ray beam is directed medially to laterally, centered on the joint line.
• Produces a true lateral orientation when the posterior aspects of the femoral condyles are superimposed.

Cues for Normal Knee X-ray, Lateral view

• Superimposed femoral condyles indicate proper positioning.
• Open the patellofemoral joint space.
• Slight overlap of the fibular head and tibia.
• Patella visualized in its trochlear groove; malposition may suggest patella alta or baja.

Skyline (Axial / Tangential / Merchant) View

This projection visualizes the patellofemoral joint and trochlear groove in profile, enabling assessment of patellar tilt, subluxation, and articular congruence. Valuable for detecting patellofemoral dysplasia, chondromalacia patellae, subluxation, and postoperative tracking abnormalities.

Techniques

• Merchant View (Superior–Inferior Beam): The patient lies supine with knees flexed to 45°, the detector placed below the knees, and the beam directed from above downward.
• Laurin View (Inferior–Superior Beam): The patient sits or lies with knees flexed 30–45°, and the beam is directed upward toward the patella.

Interpreting Normal Knee X-ray, Skyline View

• Patella should be free of superimposition with femoral condyles.
• The patellofemoral joint space should be clearly visible.
• The trochlear groove appears concave, with symmetric facets on both sides.
• Patellar tilt or lateral displacement indicates maltracking.

Intercondylar (Tunnel / Notch) View

Demonstrates the intercondylar fossa, tibial spines, and cruciate ligament insertion sites. It aids in evaluating osteochondral defects, loose bodies, and early arthritic changes in the posterior compartments. Highlights subtle osteochondral lesions, tibial spine avulsions, and posterior joint-space narrowing not evident on AP or lateral views.

Technique:

• The knee is flexed 45–50°
• The beam is directed posteroanteriorly, centered on the popliteal fossa.
• The detector is placed anterior to the knee.

Normal Knee x-ray, Skyline View

• Clear delineation of femoral condyles and intercondylar notch.
• The tibial spines should appear sharp and distinct.
• Absence of step-offs or irregularity confirms normal contour.

Weight-Bearing Views

Depict the knee under physiological loading conditions, essential for accurate evaluation of deformities and arthritic progression. Indispensable in osteoarthritis grading, valgus/varus assessment, and preoperative templating for total knee arthroplasty.

Weight-Bearing AP View

• Patient stands erect against the detector, knees fully extended and in neutral rotation.
• Demonstrates tibiofemoral joint space under load.
• Often performed bilaterally for comparison.

Rosenberg View (Weight-Bearing, 45° Flexion)

The maximum stresses in the knee joint occur between 30 and 60 degrees of flexion and therefore, standard anteroposterior weight-bearing radiographs on extension are not ideal for evaluation of cartilage loss. This view addresses this issue.

• The patient stands with knees flexed 45° and the beam angled 10° caudally.
• This position concentrates compressive forces across the posterior compartments, revealing early cartilage loss.
• More sensitive to early joint space narrowing than standard extension AP films.

Evaluation of Normal X-ray of Knee

Anteroposterior View

In a correctly done view

• The femoral and tibial condyles should be symmetrical
• The head of the fibula is slightly superimposed bit the lateral tibial condyle. [The fibula head is a great indication of rotation]
• The patella is rested on the superior portion of the image and superimposes on the distal femur.

Image evaluation lateral

A true horizontal beam lateral projection will have the following characteristic:

• Superimposition of the medial and lateral condyles of the distal femur
• An open patellofemoral joint space
• Slight superimposition of the fibular head with the tibia

The medial condyle has a medial adductor tubercle [see above] whilst the lateral condyle has a lateral condylopatellar sulcus. [see below]. Their positions can guide about the rotation of the limb.

Peripatellar fat pads should sit next to each other

Differentiating between the lateral and medial condyles on a slightly rotated lateral X-ray. Normally, they absolutely superimpose.

 The knee is generally considered to be in a true lateral position when the posterior aspects of the femoral condyles are superimposed.

The lateral view shows the patellofemoral joint, joint space between the femoral condyles and the tibia. Usually, the knee is not flexed beyond thirty degrees.

Skyline View

• Patella should be free from the superimposition of all bony structures
• Clear visualization of the patellofemoral joint space

Normal Knee X-ray Measurements

Quantitative parameters measured on knee radiographs provide objective information on alignment, patellar height, and articular congruence. Recognizing normal values and measurement techniques helps in accurate interpretation and comparison in trauma, deformity correction, and postoperative assessment.

Tibiofemoral Alignment

On a properly taken AP radiograph, the mechanical axis of the lower limb passes from the center of the femoral head through the center of the knee to the center of the ankle.

On a standard AP knee film, a simpler assessment of alignment can be made using the tibiofemoral alignment line:

• Draw a line along the lateral margin of the lateral femoral condyle.
• In a normal alignment, the lateral cortex of the tibia should not project more than 5 mm outside this line.
• Greater lateral displacement indicates valgus, while medial displacement implies varus alignment.

Typical Ranges:

• Mechanical axis passes through or within 3° of the knee center (0° ± 3°).
• The anatomic axis (femoral shaft to tibial shaft) forms a lateral angle of 174–177°, leading to about 6 degrees of valgus

Joint Space and Congruency

A parallel relationship between femoral and tibial articular margins indicates a congruent knee joint.
In the normal knee, the joint space width is 4–6 mm, equal in both compartments. Any asymmetric narrowing implies cartilage loss, meniscal degeneration, or malalignment. Apparent widening may occur transiently in the effusion or growth plate phase (children).

Tibial Slope

The posterior tibial slope represents the angle between the tibial plateau and a line perpendicular to the tibial shaft axis on the lateral view. Precise slope measurement is crucial for osteotomy planning and ACL reconstruction biomechanics.

Normal values for this are 7–10° posterior inclination. Increased slope is noted with ACL-deficient knees and may predispose to anterior tibial translation. A decreased slope or reverse slope is seen after a plateau malunion or posterior tibial wedge osteotomy.

Patellar Height Indices

• Insall–Salvati Ratio (Classic): Measured on a lateral X-ray with the knee flexed 30°.
  • A: Length of the patellar tendon (inferior patellar pole to tibial tuberosity),
  • B: Length of the patella (pole to pole).
  • Insall–Salvati Ratio = A / B
  • Normal value: 1.0 ± 0.2 [>1.2 is Patella alta,<0.8 is Patella baja]

• Modified Insall–Salvati Ratio: It uses the articular surface of the patella rather than its full height.
  • A: Distance from the inferior end of the articular surface to patellar tendon insertion.
  • B: Length of the articular surface.
  • Ratio = A / B
  • Normal value: ~1.25
• Alternative Ratios (for completeness)
  • Blackburne–Peel index: 0.8 ± 0.1
  • Caton–Deschamps index: 1.0 ± 0.2
    

These use fixed bony landmarks on the tibial plateau and patellar articular surface and may be preferred in post-arthroplasty assessment.

Read more about patellar height measurements

Normal Knee X-ray Measurements

Knee X-rays in Children

Interpreting knee radiographs in children requires familiarity with the evolving pattern of ossification, physeal orientation, and common developmental variants. The presence of multiple secondary ossification centers, open physes, and variable mineralization can easily be mistaken for fracture or pathology.

Tip: Physeal lines appear smooth, symmetric, and parallel to the joint surface. Any asymmetry, widening, or irregularity must raise suspicion for injury or growth disturbance.

Radiographic Characteristics in the Growing Knee

• Tibial Tuberosity: Fragmented appearance during growth spurts is normal. Tenderness over the tuberosity may indicate Osgood–Schlatter disease rather than avulsion.
• Physeal lines: Smooth, symmetric, parallel to joint. Any disruption suggests a physeal injury.
• Metaphyseal cupping and flaring are normal near active physes, especially the distal femur and proximal tibia. But excessive may indicate rickets.
• Epiphyseal contour: May appear irregular due to incomplete ossification. Distinguishable from fracture by lack of cortical step-off.
• Patellar appearance: Multiple ossification centers separated by radiolucent clefts. Fusion occurs gradually from the center outward.

Ossification of Knee Region

Normal Variations Often Misinterpreted as Pathology

Bipartite Patella

A bipartite patella presents as a smooth, corticated line at the superolateral aspect of the patella, without adjacent soft-tissue swelling. It is often bilateral in about half of cases. The margins are well-corticated and not sharply disrupted, distinguishing it from a patellar fracture, which shows irregular, non-sclerotic edges and associated soft-tissue reaction.

Tibial Tubercle Accessory Ossification Center

This appears as a small, separate ossicle just below the tibial tuberosity. It is a benign developmental variant often mistaken for an avulsion fracture. The key diagnostic clue is that the fragment’s edges are smooth and corticated, and it remains aligned with the patellar tendon, unlike the irregular displacement seen in true avulsion injuries.

Physiologic Genu Varum/ Valgum

Normal developmental changes in coronal knee alignment include a progression from physiologic genu varum in infancy to genu valgum between 4 and 6 years, eventually reaching a neutral or slight valgus alignment by adolescence. These are symmetrical and self-limiting changes, with the mechanical axis passing normally through the knee. Misinterpreting them as pathologic deformities should be avoided unless asymmetry, progression, or clinical symptoms are present.

Irregular Distal Femoral Metaphysis

In toddlers and young children, the distal femoral metaphysis may show slight cortical undulation or irregularity, a normal developmental feature often misread as a healing fracture. The key distinguishing point is that this pattern is bilateral and symmetric, without periosteal reaction or focal cortical disruption.

Radiographic Evaluation of Knee X-ray

A systematic evaluation approach is used for the reliable interpretation of knee radiographs. Even in an apparently normal knee x-ray, each element should be scrutinized. The standard interpretive sequence follows the ABCS format: Alignment, Bones, Cartilage, and Soft tissues, after technical adequacy is ascertained.

Technical Adequacy

Before analyzing anatomy, verify that the radiograph meets baseline quality parameters.

• Positioning: The knee radiograph should be obtained in a proper anteroposterior (AP) or true lateral projection. On the lateral view, the femoral condyles should be nearly superimposed to confirm correct positioning.
• Rotation: On the AP view, approximately one-third of the fibular head should overlap the tibia, indicating correct limb rotation. On the lateral view, the posterior femoral condyles should be superimposed.
• Exposure: Cortical bone margins should appear crisp, and the trabecular pattern should be clearly visible without evidence of over- or under-penetration.
• Weight-bearing status: The image should specify whether it was taken in the standing (weight-bearing) or supine position, as overall alignment and joint space appearance differ between the two.

Alignment

• AP View: Femoral condyles and tibial plateaus are parallel and symmetric. Mechanical axis passes near the knee center (slight medial bias normal). Fibular head overlap confirms neutral rotation.
• Lateral View: Posterior condyles superimposed. Patella aligned within trochlear groove. Tibial plateau inclination ~7–10° posterior.
• Skyline View: Patella centered in trochlear groove; joint space equal on both sides.

Any deviation suggests varus/valgus malalignment, rotational abnormality, or subluxation.

Bones

Evaluate each bony component systematically:

• Distal femur: Inspect the condylar contour, cortical integrity, and trabecular pattern. The cortical margins should appear smooth, and the trabeculae should converge symmetrically toward the condyles.
• Proximal tibia: Evaluate the tibial spines, plateau surface, and metaphyseal region. Normal findings include clearly defined tibial spines, continuous cortical outlines, and a slight concavity of the medial plateau.
• Patella: Assess the cortical outline and internal trabecular density. The cortex should be intact without any step-off or lucent area, and the trabecular pattern should appear uniform.
• Proximal fibula: Check the continuity of the cortex and its relation to the tibia. On the AP view, mild overlap with the tibia is expected, and the fibular neck cortex should remain intact.

Cartilage (Joint Spaces)

Radiographs do not visualize cartilage directly. Its thickness is inferred from joint space width and uniformity.

Also assess the subchondral bone plate for sclerosis or cysts, early indicators of degeneration.

Soft Tissues

Soft tissue detail may provide indirect evidence of joint or periarticular pathology.

• Suprapatellar pouch: Normally appears as a clear radiolucent stripe above the patella. Obliteration of this lucency suggests joint effusion.
• Infrapatellar (Hoffa’s) fat pad: Shows uniform radiolucency just below the patella. Displacement or blurring of its margins may indicate joint effusion or injury to the patellar tendon.
• Quadriceps and patellar tendon shadows: These should form continuous, well-defined soft-tissue outlines from the quadriceps to the tibial tuberosity. Thickening or loss of definition can point to tendinopathy or a partial tear.
• Prepatellar soft tissue: Normally presents as a thin, smooth contour anterior to the patella. Soft-tissue swelling or thickening in this region suggests prepatellar bursitis or cellulitis.
• Popliteal region: The area behind the knee should appear clear and free of any mass effect. Posterior fullness may represent a Baker’s cyst or a popliteal hematoma.

Role of X-rays in the Era of Modern Imaging

Even in the era of high-resolution MRI and multiplanar CT, plain radiography remains the foundation of knee imaging. Its continued primacy rests on diagnostic efficiency, biomechanical insight, and universal accessibility.

Often First Line Investigation

Radiographs are the first-line investigation for almost every knee complaint. By establishing an immediate anatomical baseline, X-rays determine when cross-sectional imaging is warranted.

Complementary to Advanced Modalities

• CT delineates complex intra-articular or comminuted fractures with precision, yet interpretation relies on orientation derived from conventional X-ray planes.
• MRI is superior for soft-tissue, cartilage, and marrow pathology, but its findings are referenced against the bony framework and axes visible on radiographs.
• Ultrasound and nuclear imaging complement functional assessment but cannot replace the structural overview that radiography provides.

Functional Assessment

Weight-bearing radiographs uniquely demonstrate joint behavior under load, revealing compartmental cartilage loss, malalignment, and mechanical axis deviation—parameters impossible to reproduce in supine CT or MRI.

Moreover, serial radiographs allow objective follow-up of fracture healing, deformity correction, osteotomy outcome, and prosthetic alignment using reproducible measurements.

Accessibility and Cost-effectiveness

Digital radiography offers rapid acquisition, minimal radiation exposure, and low cost, ensuring its utility in both tertiary centers and peripheral clinics.

Because of these advantages, radiography remains indispensable for screening, monitoring, and comparative evaluation, forming the interpretive baseline for every other imaging modality.

References

• Oksendahl HL, Gomez N, Thomas CS, Badger GD, Hulstyn MJ, Fadale PD, Fleming BC. Digital radiographic assessment of tibiofemoral joint space width: a variance component analysis. J Knee Surg. 2009 Jul;22(3):205-12. [PubMed]
• Buckland-Wright JC. Radiographic assessment of osteoarthritis: Comparison between existing methodologies. Osteoarthritis Cartilage. 1999;7:430–433. – [PubMed]
• Stiell IG, Greenberg GH, Wells GA et-al. Prospective validation of a decision rule for the use of radiography in acute knee injuries. JAMA. 1996;275 (8): 611-5. [Pubmed ]
• Seeram, E. (2023). Digital radiography: A technical review. Radiography (London), 29(2), e60–e68. [DOI]