What are signs a loculated cyst in the insertion are of the medial head of the gastrocnemius muscle the knee is getting worse?

Mass/Cyst: You may be developing a ganglion cyst, or a Baker's cyst. It is difficult to tell from your description, but if it is a fluid filled cyst, it is most likely a Gangion. If your MRI (which I am assuming you have had as you know the cyst is 'loculated') shows a solid mass, you must seek medical attention for a possible excision or biopsy for a proper dianosis