Let’s first quickly review what bruising is. Bruising is a result of capillaries (ie. small blood vessels) being damaged which then leak blood into the surrounding tissue. On the other hand, you can have swelling without bruising. This swelling is called edema.
The degree of bruising all depends on a variety of factors. The first is the invasiveness of the surgery itself. The more invasive the surgery the more bruising there will be. Therefore, surgeries such as the TPLO (tibial plateau leveling osteotomy) or TTA (tibial tuberosity advancement) or a hip surgery such as an FHO (femoral head osteotomy) or THR (total hip replacement) may in some cases have substantial bruising.
In addition to the type of surgery you also have to expect that all dogs are individuals and therefore there are simply going to be some dogs that bruise easier than others.
Whatever the cause, what is more, important is what can you do about it. Since these are a result of micro hemorrhaging the initial focus should be on icing and cold therapy, which constricts these blood vessels. The more icing the better in the early stages of recovery.
After the first three days, you can start to incorporate gentle massage into the area. You always want to start at the bottom and gently massage upwards towards the core of the body. At this point, you can also start moist heat therapy, which then relaxes, the affected muscle, improve local blood flow and help to heal the area quicker.
If the bruise appears to be getting worse at any point make sure you call your veterinarian.