Development of a Test Battery for Measurement of Knee Function in Patients With Patellar Instability

About six months after patella stabilizing surgery postoperative restrictions are commonly lifted and patients may consider whether a return to activity/sports is feasible. Currently, there are no evidence-based criteria to determine a patients readiness for sports and/or activity (RTS) following stabilizing surgery. The purpose of this project was therefore to investigate the feasibility of a test battery to evaluate knee function in postoperative follow-up evaluation - and in RTS decisions - for patients with patellar instability. Banff Patellofemoral Instability Instrument 2.0 and Norwich Patellar Instability Score is being translated and validatend in a Norwegian population. Furter is patients experience of living with patellar instability explored.

Validation of Banff Patellofemoral Instability Instrument 2.0 - No, Validation of Norwich Instability Score - No

At baseline, approximately 3 weeks before surgery and 6 months after surgery: patients conduct a testbattery consisting of 2 PROMs: the NPI-No and BPII2.0-No together with three physical tests: isokinetic strength tests, hop tests and Y-balance test. For the cross-cultural validation of NPI and BPII2.0 patients also conduct KOOS, IKDC 2000 and Tampa Scale.

Self-administered, disease-specific quality of life score. It will be administered as a patient completed questionnaire.

Patient-perceived symptoms of patellar instability during activity. It will be administered as a patient completed questionnaire.

Evaluates knee stability and asymmetrical balance in three directions (anterior, posteromedial and posterolateral).

Comprises four tasks: single-leg hop for distance, triple hop for distance, triple cross-over hop for distance and six-meter timed hop.

Strength testing of knee extension / flexion (Biodex system 4 dynamometer, Biodex Medical Systems Inc., Shirley, New York). With a standardized protocol of five repetitions at 60 o/sec and 30 repetitions at 240 o/sec.

Is a knee-specific, patient reported tool, including 18 questions across three domains: symptoms, physical activity and function. It will be administered as a patient completed questionnaire.

Is an instrument to assess the patient's opinion about their knee and associated problems. It comprises five domains: pain, other symptoms, function in daily living, function in sports and recreational activities and knee-related QOL. It will be administered as a patient completed questionnaire.

TSK is a 17-item patient-reported questionnaire aimed at quantifying the fear of re-injuries due to movement and physical activity. It will be administered as a patient completed questionnaire.

Inclusion Criteria: Patients who have undergone surgical treatment for recurrent patellar dislocation in Helse Vest. The investigators will include patients with reconstruction of the medial patella femoral ligament, trochleaplasty, tibial tubercle osteotomy, Insall or concomitant procedures. Exclusion Criteria: Unable to give written informed consent. Medial patellar dislocation. unable to understand written or spoken Norwegian. patients with other knee injuries.