My Husband Has Arthritis In His Knee...it Has Been Very

My husband has arthritis in his knee...it has been very painful recently...he has noticed swelling in his lower left leg from knee to and including ankle only in his left leg...no other symptoms like shortness of breath, etc. should he go to a walkin clinic or the hospital (it is Friday aft.) or can he wait to make an appt. with his Dr. on Monday?