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Range of motion (ROM) is one of the commonly used objective methods for clinical assessments of movement and function of the musculoskeletal system. Traditionally, it is difficult to ensure that change in ROM over a period of time can actually reflect a real change in the patient and not biased by the measuring instrumentation or process. To develop a reliable measurement device that can provide continuous feedback to the patient, this paper presents a method for angle estimation based on acceleration data acquired using a wireless sensor node. Through experiments with rotating a tri-axial accelerometer placed on the goniometer arm in various settings of rotational plane and device coordinate, a kinematic model explaining the relationship between the measurement values and the joint angles has been derived. A detailed error analysis has been performed to assess the capabilities and limitations of ROM estimation using a single tri-axial accelerometer.