Eight parameters measurable by the sensor "Orthelligent Pro" are compared with traditional measurements based on a goniometer or video taping. The aim is to inform potential users about the distribution of the differences they have to expect when moving from traditional measurement methods to the new sensor.

Patients will perform eight corresponding movement exercises at a single study visit.

In patients suffering from musculo-skeletal disorders, the restoration of full functioning is an important goal of many interventions. Assessment of functioning is often based on corresponding tests. If functioning is related to specific movement patterns, accelerometers and similar sensors are promising to allow a simple and objective assessment, and may replace traditional assessment methods, e.g. based on measurements with the goniometer. Corresponding products tend to enter the market and face clinicians and patients with the question, to which degree they are reliable and comparable with the traditional assessment methods.

Recently, a sensor named "Orthelligent Pro" has been released by the medical device company OPED and is today commercially available. The sensor - to be attached to the knee of a subject - offers the opportunity to assess several parameters related to movement patterns in the lower extremities that are of relevance in the rehabilitation process of orthopedic patients.

The aim of the current project is to inform potential users of this sensor about the difference they have to expect when compared to traditional assessment techniques of the same parameters and about the reproducibility of the measurements both based on the sensor and based on traditional assessments.

Patients of a single clinic will be offered participation. The patients will perform the eight exercises at a single study visit arranged as an addition to a routine follow up visit.

Inclusion Criteria:

• Patients after knee surgery (ACL reconstruction, total or partial knee arthroplasty, knee arthroscopy etc.) who are scheduled to a clinical follow up assessment by the surgeon between 4 months and 15 months after surgery.
• Informed consent

Exclusion Criteria:

• Age below 18 years
• Patients who underwent surgery in the lower extremities within the last 4 months
• Patients with severe acute pain
• Patients with contraindications to perform the movements/exercises
• Patients who underwent surgery also at the contralateral leg since the surgery related to the current follow up visit
• Patients who cannot follow the instructions due to language or cognitive problems

Data will be made available on request

The data will become available after publication of the study results