Ankle - Anterior View
How to perform the examination
Patient Positioning
Primary position (recommended): the patient is positioned supine with the lower limb extended and the foot in a neutral position. The ankle should be relaxed with slight plantar flexion (10–15 degrees) to optimize the opening of the anterior synovial recess. A pillow may be placed under the knee for patient comfort.
Alternative position: the patient may be seated with the leg hanging off the edge of the examination table and the foot resting on a stool. This position facilitates dynamic assessment with dorsiflexion–plantar flexion movements to evaluate the mobility of the anterior structures.
Anatomy to Identify
- Anterior synovial recess (effusion, synovial thickening)
- Talar trochlea (cartilage erosions, bone alterations)
- Tibial articular surface (sclerosis, osteophytes, erosions)
- Anterior joint capsule (thickening, adhesions, calcifications)
- Extensor tendons (secondary changes, compressions)
- Dorsal foot vessels (vascular compression)
Probe
High-frequency linear transducer (10–15 MHz) is optimal for imaging the superficial anterior structures of the ankle. Composite imaging techniques are essential to improve resolution of the articular surfaces. Power Doppler is fundamental for assessing synovial hyperemia and neovascularization processes. Frequency modulation allows analysis from superficial capsular structures to deeper bony surfaces.
Anatomical Zones
Anterior synovial recess
The anterior synovial recess of the ankle represents the anterior extension of the tibiotalar synovial cavity, located anterior to the articular surfaces of the tibia and talar trochlea. In hemophilic arthropathy, this recess is the first site of hemarthrosis accumulation and serves as an early indicator of joint disease activity.
Characteristic: Normal thickness: <2 mm, anechoic appearance in the absence of effusion
Findings:
- Hemarthrosis: Synovial fluid collection with internal echoes due to blood products at different stages of evolution
- Synovial thickening: Proliferation of synovial tissue with heterogeneous echotexture and possible increased vascularization
- Hemosiderin deposits: Scattered hyperechoic punctate echoes in the synovial fluid due to iron-derived deposits
- Synovial fibrosis: Fibrotic thickening of the recess walls with loss of normal distensibility
Probe Positioning
Place the probe transversely over the anterior surface of the ankle at the level of the tibiotalar joint line. The marker should be oriented medially. Use gentle pressure to avoid compressing the synovial recess.
Talar trochlea
The talar trochlea forms the superior articular surface of the talus, which articulates with the inferior surface of the tibia. In hemophilic arthropathy, this structure is particularly vulnerable to erosive processes due to its central position within the joint and direct exposure to lytic enzymes contained in intra-articular blood.
Characteristic: Convex pulley-shaped surface covered by hyaline cartilage
Findings:
- Cartilage erosions: Progressive loss of articular cartilage with irregularity of the trochlear surface
- Subchondral bone changes: Sclerosis or formation of subchondral cysts (geodes) due to bone remodeling
- Trochlear flattening: Loss of normal convexity due to extensive erosive processes
- Marginal osteophytes: Osteophytic formations at the trochlear edges as a response to degenerative changes
Probe Positioning
Perform longitudinal and transverse scans centered on the talar trochlea, placing the probe just distal to the anterior tibial malleolus. Optimal visualization is achieved with the foot in dorsiflexion.
Anterior articular capsule
The anterior articular capsule of the ankle is a fibrosynovial structure that forms the anterior boundary of the tibiotalar joint cavity. In hemophilic arthropathy, the capsule undergoes progressive structural changes characterized by thickening, fibrosis, and adhesion formation, which significantly limit joint mobility.
Characteristic: Normal thickness: 1–2 mm, homogeneous hypoechoic echotexture
Findings:
- Capsular thickening: Marked increase in thickness with heterogeneous echotexture due to fibro-inflammatory processes
- Capsular calcifications: Calcific deposits within the fibrous portion of the capsule, especially at bony insertions
- Intra-articular adhesions: Fibrous bands connecting articular surfaces and limiting dorsiflexion movements
- Equinus contracture: Capsular retraction causing limitation of dorsiflexion and plantar flexion posture
- Proliferative synovitis: Thickening of the synovial layer of the capsule with possible invasive synovial pannus
Probe Positioning
Place the probe longitudinally on the anterior surface of the distal tibia, extending to the superior surface of the talus. Dynamic flexion-extension movements of the foot are essential for capsular evaluation.
Clinical Cases by Severity grade
The clinical cases are organized according to the HEAD-US protocol (Head-to-Head Assessment of Ultrasound Score), which classifies the severity of hemophilic arthropathy into four levels. Click on each level to explore the available cases for that specific joint–projection combination.