Started limping nearly 2 years after major surgery

[Noitsnotteatimeyet]

Nearly 2 years ago our ex-Dubai street cat got hit by a car and shattered his pelvis. Several thousand pounds of surgery later and after three months of house arrest he seemed to have made a full recovery.

However in the last couple of weeks I've noticed that when he runs he's developed a limp. It's not stopping him from patrolling his territory, jumping up onto ridiculous heights, imposing his will on the neighbourhood cats and sitting on our front wall chatting to passers-by but ... he's definitely limping

Could the pins holding his pelvis together be coming loose? Or could he have developed arthritis in that joint (but he's only 5 or 6 - don't know for sure)