Tai Chi for Reducing Aromatase Inhibitor-Induced Arthralgia

The objective of the pilot RCT is to evaluate the feasibility and acceptability of a Tai Chi intervention "TaiChi4Joint" vs. an HE AC group for relieving AIIA in women with hormone receptor positive stage I-III BCa. The investigators will pilot test our data collection for mechanism measures via three innovatively integrated biobehavioral pathways.

Inclusion Criteria: -Individuals must meet all the following inclusion criteria in order to be eligible to participate in the study: * Age ≥18 years * Diagnosis of stage I-III hormone receptor-positive breast cancer * Postmenopausal * Currently receiving an aromatase inhibitor (anastrozole, letrozole, or exemestane) or within 5 years of initiation * Report joint pain that started or worsened after initiation of AI therapy * Report worst pain in the past week ≥3 on the BPI (0-10 scale) * Able to complete study procedures in English * Willing to be randomized to an intervention or attention control group and adhere to study procedures Exclusion Criteria: -An individual who meets any of the following criteria will be excluded from participation in this study: * Undergoing active cancer treatment (excluding endocrine therapy) * Uncontrolled cardiac or pulmonary disease that would limit safe participation * Currently engaged in regular structured moderate- or vigorous-intensity exercise (e.g., brisk walking, jogging/running, cycling, swimming, aerobic classes, or resistance training) totaling ≥150 minutes per week over the past 3 months * Currently participating in Tai Chi, yoga, Pilates, or other structured mind-body practice ≥2 times per week over the past 3 months * Joint pain due to inflammatory arthritic conditions * Recent surgery or joint injection within the past 4-6 weeks * Initiation or dose change of corticosteroids or opioids within the past 4 weeks * Planned discontinuation of AI therapy within the next 6 months * This study is limited to women with breast cancer, as \