A system for determining a change in position of an implanted medical device (100, 600, 700, 800, 900) within an implant pocket, the system comprising: an accelerometer (103, 770, 956) configured to be implanted in a patient, the accelerometer configured to obtain accelerometer data along at least one axis; memory (760, 952) configured to store program instructions; one or more processors (721, 964) that, when executing the program instructions, are configured to: determine the patient is engaging in a determined activity over an activity period; obtain the accelerometer data during the activity period; identify postures of the patient and corresponding posture periods during the activity period based on the accelerometer data; determine a duration related to a non-standing posture identified from the postures identified; and identify a migration of the IMD (100, 600, 700, 800, 900) within the implant pocket based on the duration of the non-standing posture exceeding a duration threshold, characterized in that the one or more processors (721, 964) are further configured to: determine the migration of the IMD (100, 600, 700, 800, 900) within the implant pocket based on the accelerometer data; and suspend obtaining the accelerometer data when the migration exceeds a migration threshold. an accelerometer (103, 770, 956) configured to be implanted in a patient, the accelerometer configured to obtain accelerometer data along at least one axis; memory (760, 952) configured to store program instructions; one or more processors (721, 964) that, when executing the program instructions, are configured to: determine the patient is engaging in a determined activity over an activity period; obtain the accelerometer data during the activity period; identify postures of the patient and corresponding posture periods during the activity period based on the accelerometer data; determine a duration related to a non-standing posture identified from the postures identified; and identify a migration of the IMD (100, 600, 700, 800, 900) within the implant pocket based on the duration of the non-standing posture exceeding a duration threshold, characterized in that the one or more processors (721, 964) are further configured to: determine the migration of the IMD (100, 600, 700, 800, 900) within the implant pocket based on the accelerometer data; and suspend obtaining the accelerometer data when the migration exceeds a migration threshold. determine the patient is engaging in a determined activity over an activity period; obtain the accelerometer data during the activity period; identify postures of the patient and corresponding posture periods during the activity period based on the accelerometer data; determine a duration related to a non-standing posture identified from the postures identified; and identify a migration of the IMD (100, 600, 700, 800, 900) within the implant pocket based on the duration of the non-standing posture exceeding a duration threshold, characterized in that the one or more processors (721, 964) are further configured to: determine the migration of the IMD (100, 600, 700, 800, 900) within the implant pocket based on the accelerometer data; and suspend obtaining the accelerometer data when the migration exceeds a migration threshold. determine the migration of the IMD (100, 600, 700, 800, 900) within the implant pocket based on the accelerometer data; and suspend obtaining the accelerometer data when the migration exceeds a migration threshold.