Knee - Lateral View
How to perform the examination
Patient Positioning
Primary (recommended) position: the patient is positioned in a contralateral lateral decubitus (with the side to be examined facing upward) or in a supine position with the knee internally rotated to expose the lateral compartment. The knee should be kept in slight flexion (15–20 degrees) to optimize visualization of the ligamentous and meniscal structures.
Alternative position: the patient may be positioned supine with the hip abducted and externally rotated, allowing lateral access to the knee.
This position facilitates dynamic examination and functional assessment of the structures within the lateral compartment.
Anatomy to Identify
- Lateral collateral ligament (lesions, thickening, calcifications)
- Lateral meniscus (tears, degeneration, extrusion)
- Biceps femoris tendon (tendinopathies, partial/complete tears)
- Iliotibial tract (friction syndrome, thickening)
- Lateral joint capsule (synovial thickening, effusions)
- Common peroneal nerve (compression, morphological alterations)
Probe
A high-frequency linear transducer (7–15 MHz) is essential for evaluating the superficial structures of the lateral compartment. It is crucial to use beam steering techniques to overcome anisotropy of the lateral collateral ligament.
Doppler capability is fundamental for assessing synovial vascularization and inflammatory processes. Adjusting the transducer frequency allows optimization of imaging for both superficial and deeper structures within the lateral compartment.
Anatomical Zones
Lateral meniscus
The lateral meniscus is a C-shaped fibrocartilaginous structure that is more mobile than the medial meniscus. In hemophilic arthropathy, the lateral meniscus may show early degenerative changes due to biomechanical alterations caused by repeated hemarthroses and chronic synovial thickening.
Characteristic: Shape: C-shaped, greater mobility compared to the medial meniscus
Findings:
- Myxoid degeneration: Increased internal echogenicity with loss of the normal triangular structure.
- Meniscal tears: Longitudinal tears, bucket-handle lesions, intrasubstance calcifications.
- Meniscal extrusion: Protrusion beyond the tibial margins due to chronic capsular laxity.
- Meniscal cysts: Cystic formations adjacent to the meniscus, often communicating with intrasubstance tears.
Probe Positioning
Perform transverse and longitudinal scans at the level of the lateral joint line. The probe should be positioned just anterior to the lateral collateral ligament, with optimal visualization obtained through varus stress maneuvers.
Biceps femoris tendon
The biceps femoris tendon represents the lateral insertion of the posterior thigh muscles onto the head of the fibula. In hemophilic arthropathy, this structure may be involved in postural and compensatory alterations that develop secondary to chronic joint changes.
Characteristic: Insertion: Fibular head, normal thickness: 4–6 mm
Findings:
- Compensatory tendinopathy: Reactive thickening due to biomechanical alterations of the knee.
- Tendinous calcifications: Calcific deposits along the tendon course in patients with chronic arthropathy.
- Associated bursitis: Inflammation of adjacent bursae, possibly communicating with hematoma collections.
- Insertional changes: Enthesopathy at the fibular head with irregularity of the bony surface.
Probe Positioning
Place the probe longitudinally along the tendon course from the muscle belly to its insertion on the fibular head. The probe marker should be oriented proximally toward the thigh.
Clinical Cases by Severity grade
The clinical cases are organized according to four levels of severity of hemophilic arthropathy. Click on each level to explore the available cases for that specific joint–projection combination.