Variation in patients' independent exercise and activity after total knee arthroplasty (TKA) surgery may contribute to variable functional gains but have never been quantified. We pilot tested daily exercise logs and step activity monitors to quantify exercise and general home activity post-TKA. Patients successfully maintained logs and wore activity monitors. Logs documented significant variation in quantity of daily exercises. Women with poor emotional health recorded fewer repetitions and greater variation. More daily exercise repetitions correlated with larger 6-month functional improvement. Activity peaks on step monitors correlated with logged exercise sessions. However, most step activity was in addition to exercise sessions. Further research is needed to validate these findings and to clarify the relationship among post-TKA exercise, activity, and functional gain.