Here are a few things to keep in mind when advancing your client.
1)Is their diagnosis recent or long standing?
You must find out whether the condition is acute (days old), subacute (weeks old) or chronic (months old). If it is acute, you should be cautious, and advance intensity slowly. If chronic, you may be more aggressive.
2) What is your client's reactivity?
Ask yourself: "Does a little activity causes a great deal of pain?" If so, you need to modify.
3)Is the problem an inflammatory or mechanical issue?
Acute inflammation may present as red, swollen, hot. It is usually better with activity due to the "moving around" of inflammatory chemicals. Chronic inflammation presents with no resting pain, but may be worse with activity. Is the activity you are performing creating more inflammation, rather than "flushing out" the inflammatory agents? With Mechanical issues, pain increases with activity and is better with rest. However, there is no redness, swelling, or warmth. If you adjust the mechanics, does the pain diminish?
4) What is the seriousness or severity of the condition?
Is it a serious pathology that may worsen upon increased activity (Multiple Sclerosis, torn tendon/ligament, etc...)
So these are a few things to keep in mind when initiating a progression in your client's program. They will help with your client's health and comfort level, his/her confidence level in you, the longevity of your relationship with your client, the speed of your client's recovery, and his/her return to a healthy fitness lifestyle.