The coronoid fossa is a bony depression located on the anterior surface of the distal humerus, which accommodates the coronoid process of the ulna during elbow flexion. In hemophilic arthropathy, this structure may show significant bone alterations due to the erosive and proliferative processes characteristic of chronic joint disease.

Characteristic: Normal depth: 2–4 mm, smooth and regular surface

Findings:

• Marginal osteophytes: Osteophytic formations at the margins of the fossa due to chronic degenerative processes.
• Bone erosions: Areas of bone loss with irregularity of the fossa profile.
• Loose bodies: Free osteochondral fragments within the fossa, resulting from erosive processes.
• Subchondral sclerosis: Increased echogenicity of the subchondral bone due to chronic remodeling.

Probe Positioning
Place the probe longitudinally on the anterior surface of the distal arm, centered over the coronoid fossa of the humerus. The probe marker should be oriented proximally toward the arm. Apply gentle pressure to avoid compressing the superficial structures.

The coronoid process of the ulna is the anterior bony prominence of the proximal ulna that articulates with the coronoid fossa during flexion movements. In hemophilic arthropathy, this structure is frequently involved in the erosive processes characteristic of the disease, leading to morphological and functional alterations.

Characteristic: Morphology: triangular, smooth articular surface covered by cartilage

Findings:

• Cartilage erosions: Focal or diffuse loss of articular cartilage with exposure of the subchondral bone.
• Profile irregularities: Morphological changes of the process due to erosive and reparative processes.
• Periarticular calcifications: Calcific deposits in the soft tissues adjacent to the coronoid process.
• Bone fragmentations: Small bone avulsions due to repeated mechanical stress on weakened bone tissue.

Probe Positioning
Perform transverse and longitudinal scans at the humeroulnar joint, positioning the probe on the anteromedial surface of the elbow. Optimal visualization is achieved with the elbow slightly flexed.

The anterior joint capsule of the elbow is a fibro-synovial structure that anteriorly defines the joint cavity. In hemophilic arthropathy, the capsule undergoes significant structural changes characterized by synovial thickening, fibrosis, and adhesion formation, which severely compromise joint mobility.

Characteristic: Normal thickness: 1–2 mm, homogeneous hypoechoic appearance

Findings:

• Synovial thickening: Marked increase in capsular thickness with heterogeneous echotexture.
• Joint effusions: Anechoic or hypoechoic synovial fluid collection in the anterior joint cavity.
• Synovial proliferation: Hyperplastic synovial tissue with possible increased vascular component on Doppler.
• Intra-articular adhesions: Fibrous bands connecting opposing joint surfaces, limiting motion.
• Capsular calcifications: Calcific deposits within fibrotic portions of the capsule, particularly in advanced chronic stages.

Probe Positioning
Place the probe transversely on the anterior surface of the elbow at the level of the joint line. A dynamic scanning technique with flexion-extension movements is required to assess capsular distensibility.