Ulnar nerve injuries often lead to muscle atrophy and reduced hand function, necessitating precise monitoring and effective rehabilitation strategies. Current grip strength measurement tools rely on rigid mechanical equipment, which is inconvenient and requires frequent calibration. To address this, a muscle atrophy evaluation and rehabilitation system (MUERS) is presented, featuring a highly sensitive rare earth oxide-enhanced triboelectric sensor (RETS). Utilizing the unique electrochemical properties of rare earth oxides, RETS demonstrates a linear voltage-force response in the range of 8–80 kPa, with a maximum linear error of 1.5%. Integrated with a multi-channel STM32 signal collector, RETS enables real-time grip strength monitoring across all five fingers. Combining sensor output with an SVM algorithm, the system achieves 98.61% accuracy in identifying finger grip strength injuries and classifies damage into three levels with an average accuracy of 96.67%. MUERS evaluates rehabilitation progress by scoring grip strength and providing feedback to clinicians. Over a four-week cycle, it consistently captures improvements in muscle recovery, aiding individualized rehabilitation plans. This system offers fine-grained assessment capabilities for diagnosing and monitoring nerve injury-induced muscle atrophy, paving the way for advanced biomedical sensing and personalized rehabilitation.