There are no official guidelines to assist in answering this question. I will search for relevant research papers instead.
From the Research
Muscle Pain with Internal Rotation of the Shoulder
- The subscapularis muscle is the primary internal rotator of the shoulder and plays a key role in causing adduction, internal rotation, and pain in the hemiplegic patient 1.
- Decreased subscapularis strength resulted in a significant increase in maximum external rotation and increased glenohumeral contact pressure, which may lead to rotator cuff tears and type II superior labrum anterior and posterior lesions 2.
- During internal rotation, significantly higher activity levels were found in subscapularis, indicating its role as an internal rotator of the shoulder 3.
- Posterior shoulder muscle stiffness, including the infraspinatus and teres minor muscles, was correlated with internal rotation, suggesting that these muscles may also contribute to pain with internal rotation 4.
- Increased stiffness of the pectoralis major, teres major, and latissimus dorsi muscles was observed in patients with hemiplegic shoulder pain, and the stiffness of the teres major muscle was associated with pain intensity and shoulder mobility 5.