LH maintains relations with a number of carriers that have left the *A. A prime example is AA who merged with US Airways. LH still uses US former hub in CLT and interlines to AA destinations in the Carribean. If there are destinations served by SK only and LH wants to sell tickets there, they will make arrangements to sell thru tickets and interline with SK. So you will be able to travel without issues, but will not be able to use the *A priviledges (baggage allowance, lounge etc).