The aim of the present study was to analyse and describe muscle function, quality of life and functional capacity before and after shoulder instability surgery. Twenty-six women aged 34 (± 14) years and 95 men aged 32 (± 10) years participated in this study. All patients were on the waiting list or had undergone shoulder instability surgery. The study was performed with a cross-sectional design and patients were examined pre-operatively, 6-month post-operatively or 7-year post-operatively. Handgrip strength measurement, active range of motion (AROM), isometric shoulder muscle strength measurement, health-related quality of life measured by Western Ontario Shoulder Instability Index (WOSI©) and shoulder function using the Constant Score were evaluated. The mean AROM in flexion for women in all groups ranged from 162° (± 16) to 169° (± 12), and for men from 157° (± 19) to 162° (± 12). The mean AROM in abduction ranged from 170° (± 25) to 177°(± 5) for women and from 177° (± 8) to 179° (± 24) for men. The mean AROM in external rotation ranged from 89° (± 14) to 95° (± 14) for women and from 83° (± 21) to 85° (± 12) for men. Men were significantly stronger and had a larger AROM on the non-injured side compared with the injured side, whereas differences were found between non-injured and injured side for women only in AROM. The scores from the WOSI© for all the patients were far from normative values suggesting that the patient's subjective experience does not fully reflect the physical examination. The results from the present study can guide the physiotherapist to give patients realistic expectations of shoulder function concerning AROM and muscle strength.