Can Clindamycin cause stiffness?

No, I took it for 6 months after surgery but the possible side effects are nausea, vomiting, diarrhea, stomach pain, and 20% of people have pain when swallowing. Less common are rash, hives, itching, difficulty breathing, yellowing of the skin or whites of the eyes, colitis and joint pain. These are all less common. It sounds more like you are getting a cold or a bug. Take some Tylenol for the fever, it will help the stiffness but you might want to think of getting some cold & flu medication from the store. It's not the antibiotic causing your problem.