Background: Arthroscopy and splint bone removal are the common orthopedic procedures in horses. Estimation of the dynamics of acute phase proteins in postoperative monitoring seems to be interesting diagnostic approach. The aim of the study was to investigate changes in the concentrations of plasma inflammatory markers—fibrinogen, haptoglobin, and protease inhibitors—following orthopedic surgery in horses. The study involved 114 horses, divided into two study groups undergoing: arthroscopy (41 horses) and splint bone removal (13 horses). The control group consisted of 60 healthy horses. The blood was collected before the surgery and 24, 48, 72 h, 5, 7, 10, 14 and 28 days after the surgery. Plasma fibrinogen, serum haptoglobin and proteinase inhibitors were measured. Results: In non-complicated cases of arthroscopy and splint bone removal, fibrinogen and haptoglobin increased stepwise from 24 h, achieved the maximum level at 72 h and returned to preoperative levels after 10–14 days. In one complicated case after arthroscopy surgery the marked increase in fibrinogen and haptoglobin concentrations was observed 24 h earlier than standard parameters of inflammation Conclusion: The study shows the evolution of APPs after arthroscopy and splint bone removal in 28 days postsurgery period and in the case of one complicated case of arthroscopy.