Joint stability is essential for maintaining normal everyday function. However, assessment of stability often still relies on subjective or obtrusive methods. An unobtrusive approach would be to have our clothes assess our joint stability. Methods. A new application consisting of an attachable clothing sensing system (ACSS), constructed from a flexible carbon black and polyurethane composite film, was tested against an optical tracking system to assess if the ACSS placed across the knee could provide stability results that correlate with the optical tracking outcomes. Stability was challenged by reducing the base of support and by removing vision generating different experimental conditions. Results. Bland and Altman plots indicated a general proportional error between the measurement systems within each stability condition. However, across all conditions a Spearman correlation coefficient of 0.81 () was found between the displacement values and ACSS, showing a good association between stability measurements. Electromyography (EMG) also indicated that joint stability was challenged between the different conditions. The ACSS was experienced by users as comfortable and hardly noticeable. Conclusions. This study indicates that smart clothing can measure important physiological parameters in an unobtrusive manner. This “wear and measure” approach might change how we gather relevant clinical data in the future.