The aim of this study is to evaluate the possibility of establishing a patient-based ultrasound monitoring of the knee (representing a target joint accessible with any hand) with a handheld device:

The following questions will be answered:

1. What is necessary for the organisational implementation of a patient-based ultrasound monitoring in patients with haemophilia?
2. Is it possible to train patients with haemophilia to perform sonography of their target joints?
3. Does a patient-based ultrasound monitoring with a handheld device work in a home setting?
4. What is the quality of the patient's self-acquired ultrasound images?
5. Will the test persons be able to distinguish normal findings from (any) pathologic findings?

Inclusion Criteria:

• Adult patients (≥ 18 years of age) suffering from severe haemophilia A or B
• No professional medical background
• Submitted written consent to participate in the study and to use their study related pseudonymized data

Exclusion Criteria:

• Patients suffering from other bleeding diseases
• Participants < 18 years of age
• Participants without written consent
• Professional medical background

Adult patients (≥ 18 years of age) suffering from severe haemophilia A or B. Haemophilia is an X-linked recessive genetic bleeding disease characterised by absence or deficiency of factor VIII in haemophilia A or factor IX in haemophilia B. This can cause spontaneous bleedings, particularly into joints. Joint bleedings initiate an inflammatory process characterised by chronic synovitis that causes degeneration of the affected joints and results in haemophilic arthropathy

The publication of anonymous patient data is not allowed by informed consent.