Function, measured with physical tests and patient reported outcome measures, six months after surgery for patellar instability. A cross-sectional study

Background: Patellar instability can limit activity and participation for many young people, and more knowledge is needed to assess this complex condition. The aim of this study is to collect physical, and patient reported information about knee function in persons six months after surgery for patellar instability. The purpose is to contribute to the development of a test-battery to guide safe return to activity and sports for this group of patients. The data is collected for an ongoing project at The University in Bergen. Methods: This study is a quantitative study with a cross-sectional design, and the data were collected from physical tests (isokinetic strength tests, Y-balance test and single-leg hop tests) and patient reported outcome measures (NPI and BPII 2.0). Limb symmetry index (LSI) was calculated at the physical tests. Pearson’s r correlation coefficients were calculated to assess the relationships between the patient reported outcome measures (PROMs) and the physical tests and the relationship between the two PROMs. Statistical significance was defined as p ≤ 0.05. Results: The Y-balance tests show good results six months postoperatively (95% LSI). Isokinetic knee extension, single hop and triple hop tests show low LSI (73 to 89% LSI). Further, the results show weak correlation between physical tests and the PROMs. NPI and BPII2.0 were strongly correlated (-.595). Conclusions: There is a need for rehabilitation beyond six months, if the aim is to participate in sports. In the rehabilitation it is important to consider both physical aspects and the patient's own experience of the situatio