Inclusion Criteria:

1. Aged over 18 years old;
2. Head and neck cancer patients must have completed radiotherapy for at least 3 months;
3. Those whose mouth-opening distance is less than or equal to 3.5 cm (the functional cut-off point of trismus) and who have tightness or pain in the masticatory muscles;
4. Medical condition is stable;

Exclusion Criteria:

1. Those who have undergone surgery on their masticatory muscles;
2. Patients with obvious muscle atrophy or complete fibrosis of masticatory muscles ;
3. Those with tumor recurrence at the time of admission;
4. Those whose vital signs are unstable due to acute illness.