I saw you write somewhere recently that subscapularis dysfunction was generally associated with posterior capsule tightness? Is there a causal relationship?
The subscapularis, infraspinatus, and teres minor work together to depress the humeral head during dynamic shoulder activities.
The subscapularis posteriorly pulls the humeral head in the joint (counteracts pectoralis major), while the other two anteriorly pull it (counteract posterior deltoid).
So, they're antagonists and synergists at the same time.
If subscapularis shuts down, infraspinatus and teres minor fire overtime as depressors - but you don't get subscapularis’ posterior humeral head pull. Tightness kicks in with the posterior capsule, and you can also get anterior humeral glide issues. This is a big no-no in overhead throwing, as they’ll look to the elbow to get range of motion – and that’s when you start to see ulnar collateral ligament ruptures, ulnar nerve compression, etc.