I'm going to my sports med dr today. he gives me cortisone shot in my knee. my knee is locking up and crackling sound & sharp pains. what can i do.

See details: I am not in favor of repeated cortisone injections especially in a 22 year old knee. You need an MRI even if one has been done previously and then you need a second opinion.

Further workup: You may want to consider further workup and discussions with your surgeon about other options for treatment rather than getting multiple steroid injections.

Trust your doctor: you need to have MRI to find out what is wrong with your knee. see a knee specialist for evaluation and advises. keep up with the exercise they give you to improve the knee function. follow up with your doctor. trust your doctor.