If the land surrounding the property is homeowner association owned (likely- it's a condo, right?) then you need to review the offering plan carefully. Many condo communities permit nothing in the way of changes to the exact landscape/exterior plan (I recall one where an owner planted some flowers at the foundation and was told to remove them). A dog run or enclosed area could be problematic- anything that interferes with the maintenance agreed to in the docs is a question that you need answered by architecural control (the management company should be able to provide you with the #)- a dog pen (even on a patio) alters the "look", in addition to potentially interfering with maintenance depending on, (as Bill mentioned) the current restrictions- each community is different.
This is a question best directed to the condo association. These guidelines vary greatly from association to association and can change quite often, making it extremely to keep track of this information.