Yоu hаve gоtten yоur 10 а.m. pаtient back that is post-op TKA, you notice that the patient is limping really bad on the surgical leg. After talking with the patient, you find out that the calf is really tight and painful. You check the surgical leg and find that the calf is red, swollen, hot, and painful to the touch. You have a positive Homans test. Which of the following should you suspect?