There will always be risks to surgery, but these can be kept to a minimum by proper patient selection and careful preparation.

The risks are of two types – those related directly to the operation and those that could affect your health in general.  The specific operation risks are covered in the sections on individual procedures but the most important are infection, bleeding and poor wound healing.

Infection –

This develops when bacteria get into the operation site and multiply causing pain, swelling, heat and redness.  The organisms can get there from the patient’s own skin or from the environment at the time of surgery, or at a later date from the patient’s blood stream if there is infection elsewhere.

Infection is always a serious complication and everything should be done to prevent it developing.  Some people have an increased risk such as having diabetes or some skin rashes such as psoriasis.  Any local infections or wounds such as cuts, grazes or animal scratches will mean your surgery is likely to be delayed until they have healed up.  Surgery is always performed in a very clean environment, but careful skin preparation is also very important.  The area for surgery is likely to be shaved, but please leave this to the operating team and don’t do it yourself – again any nicks or scratches means a delay.

Antibiotics are often given by injection to help prevent infection at the time of surgery.

Bleeding –

Some bleeding is almost inevitable but should always be kept to a minimum.  Again, prevention is key.  Some medications cause increased bleeding because they inhibit blood clotting.  Warfarin, aspirin and Clopidogrel are the most common.  They can usually be stopped before surgery in consultation with your surgeon, but they need to be stopped at different times as they can keep working long after the last dose.  As general guidance Warfarin should be stopped 5 days pre-op, aspirin 5 days and clopidogrel as much as 10 days pre-op.  Instructions are usually clear in your pre-op information pack, but if you are on any of these medications, please ensure you tell your surgeon.

Wound healing –

Poor wound healing is more of a problem at some sites than others and around the knee it is usually straightforward unless you have had a lot of previous surgery.  Once again, there are some risk factors.  Poor would healing is related to poor general health, diabetes, a poor immune system, poor circulation, marked swelling such as lymphoedema, smoking and obesity.  The risk of poor healing is the development of more serious deep infection so it is important to get a well healed wound as quickly as possible.


General complications

Blood clots –

Operations on the lower limb carry a significant risk of producing a blood clot in one of the deep veins of the leg – known as a DVT.  If this occurs, the leg becomes swollen, painful and difficult to walk on.  It can develop from very early after surgery up to as much as 3 months post-op.  If a clot breaks off and travels to the lung (pulmonary embolism) then chest pain, breathlessness, a cough with blood-stained sputum or even complete collapse can occur.

Again, prevention is most important.  Risk factors such as smoking, obesity, taking the contraceptive pill or HRT, a past history of blood clots or even a family history must be taken into account.  The usual measures taken are to get as mobile as possible as quickly as possible after your surgery.  Devices such as foot or calf pumps may be used, or compressive stockings.  After more major surgery such as knee replacement, you may be given a series of injections to inhibit blood clotting or you may have some tablets to take that do much the same thing.  By taking these measures, the risks are very low.

Those patients at very high risk due to an abnormality of clotting or a past history of blood clots will need to take Warfarin or an equivalent for at least 3 months after major knee surgery.  Those same patients may already be on Warfarin long term.  This will need to be stopped 5 days before surgery and then re-started 2 days later with the intervening period covered by injections of heparin.

We know that the risk of getting blood clots is increased by long-haul flights - thought to be due to a combination of immobility and dehydration.  It makes sense that these conditions will yet further increase the risks of blood clots after knee surgery.  There is very little science on which to base advice, but it seems sensible to avoid short-haul flights for 6 weeks after major knee surgery and long-haul flights for as much as 3 months.  If you do have to fly, it is advised to take the following precautions -

  • Walk around the cabin occasionally to avoid being totally immobile
  • Use compressive flight socks
  • Keep well hydrated and avoid alcohol
  • Consider taking Aspirin at low dose (75mg daily) starting 5 days before you fly

Chest infections –

If you already have poor breathing or if you smoke, then you have an increased risk of getting a chest infection after your surgery. If you already have a heavy cold, cough or chest symptoms, then surgery will be postponed until you have recovered.  One particularly nasty complication is severe infection and lung damage that can occur if you inhale stomach contents.  This is why you are asked to be starved before surgery – usually for 6 hours.  This includes chewing gum as it encourages the stomach to fill up with saliva and acid.

Heart problems –

There is an increased risk of heart attack after surgery.  This is really only possible if you already have significant heart disease, but it is important that your blood pressure is well controlled.  If there are concerns, then screening tests may be needed such as an ECG and an Echocardiogram may be advised.


Key points –


If you want to be as safe as possible and avoid being cancelled on the day –


  • Read the pre-op information
  • Avoid any scratches or infections around the knee
  • Call in and cancel if you have a chest infection or heavy cold
  • Stop medications as advised by your surgeon
  • Follow starving instructions – including no chewing-gum
  • Stop smoking
  • Lose weight
  • Get mobile











Alexandra Hospital
0161 495 7000/1/2/3
Spire Manchester
0161 447 6600
Practice Manager
0161 495 6869