Whilst we all know that the knee is the joint between the top of the shin bone (tibia) and the bottom of the thigh bone (femur), what you might not be aware of is exactly how complex a biomechanics like structure it is . You would be forgiven for thinking of the knee as a simple hinge joint. However this is not the case as rotation at the knee also occurs as part of its normal action. Like all large joints in the body, the joint surfaces of the knee are covered in what is known as hyaline cartilage. This cartilage not only protects the knee against stress and absorbs shock ,but also creates a very low frictions surface to help it function efficiently .

As we age, this “cushioning” cartilage can wear away naturally as well as become roughened . Also, damage can occur prematurely due to infection or trauma ( including sport) . When this loss of high quality smooth shock absorbing material occurs ,either as a part of the natural ageing process or prematurely due to inherited factors, it is known as Osteoarthritis (OA) As this cushioning cartilage gradually thins, the knee has less and less protection against shock and the bone ends can become “injured” even by day-to-day activities such as walking. The underlying bone can then become inflamed, which in turn can produce dull aching pain.  The symptoms of osteoarthritis include:

This, in turn, can then result in:

When the level of pain becomes intrusive and disruptive to daily life, this is the point at which all treatment options should be considered including surgery.

Diagnosing osteoarthritis of the knee

Diagnosis involves listening to the patient’s history during the consultation, examination of the patient and the use of specialised tests.  Plain weight-bearing radiographs (x-rays) of the knee are taken to see how much cartilage has been lost. They will also show if there is any deformity in the knee or extra bone formation (osteophytes). These are caused by bone rubbing on bone due to the loss of cartilage. 

Treatment options

It is preferable that osteoarthritis is treated conservatively (without surgery) for as long as possible. However, the need for replacement of the joint may ultimately become inevitable, due to deterioration in the condition of the joint leading to increased disability and pain.

Conservative treatment

Conservative (non-invasive) treatment of knee osteoarthritis involves a combined approach: 

  1. Physiotherapy/muscle strengthening 
  2. Pain management with tablets or joint injections
  3. Weight loss 

I believe strongly that physiotherapists have a significant role in keeping patients away from the need for surgical intervention for as long as possible. The pain from arthritis can be helped significantly, often for many years, by the intermittent, rather than regular, use of non-steroidal anti-inflammatory (NSAI) medication. 

On occasions, some patients will be considered suitable for a series of hyaluronic acid injections into the knee as a part of the treatment referred to as viscosupplementation. These injections help to lubricate the degenerating joint surface and can be very effective in a small majority of ‘early’ cases. 

Similarly, there is a role for the use of injected steroid into the knee when/if acutely inflamed but is usually considered in rare episodes of extreme discomfort. Weight loss, if appropriate, will reduce stress on the knee. Also some braces can offload the damaged part of the knee . Hopefully, with conservative management, patients can avoid the need for surgery for many years after the onset of arthritis. 


Before and after knee replacement
Oxford unicompartmental knee replacement
Total knee replacement

Opting for Surgery 

Knee replacement surgery, like all joint replacement surgery, is a very major operation and requires careful consideration and discussion before proceeding.

If, however, the patient and surgeon have come to the decision that there is little alternative, replacement surgery can offer immense symptomatic relief to the patient. 

Knee replacement surgery can be divided into total knee replacement surgery or unicompartment replacement surgery. In both cases, the operation is carried out under a light general anaesthetic with regional anaesthesia (spinal) and lasts approximately one to one and a half hours. 

Total knee replacement surgery involves the replacement of all aspects of the joint (including the kneecap) with an artificial bearing surface. 

Surgery restores the normal alignment of the joint, as well as the smooth articulating surface that has been damaged by osteoarthritis. 

This surgery also restores the normal alignment of the soft tissues (ligaments/muscles) around the bone so that the knee continues to work in as near to normal a fashion as it did before the arthritic process started. 

Understanding the risks

As with all operations, it is very important that you fully understand the ‘pros’ and ‘cons’ before electing to proceed with surgery. Whilst the benefits are clear, time must be given to discuss ‘what can go wrong’.  The main risks of knee replacement include: 

Whilst all of these complications are extremely rare, they can and do occur. 

Patients usually stay in hospital for 4 to 5 days.. During this time you will have daily physiotherapy.  Patients are ready to leave hospital when they can: 

After surgery

The wound will be checked by me at two weeks after the surgery but as the sutures are all under the skin and are absorbable they will not require removal =.

I then review most patients after another six weeks to check on their progress.  My main concern is to ensure that the wound is healing well and that the swelling is beginning to reduce. However, you should expect the knee to be swollen for some months and therefore your flexibility will be quite markedly restricted by this swelling. 

Only when the swelling has diminished and the knee is moving well can you start to build up the muscle that will have wasted away in the preceding months. Physiotherapy is a vital part of the recovery process and needs to be arranged in advance of the operation starting again very soon after you leave the hospital.

Recovering from a total knee replacement operation takes time; sometimes it takes as long as a year for the knee to feel comfortable again. 

Interrupted sleep, unfortunately, is normal in the first three months after such major surgery and you should be prepared for this. 


This form of knee replacement surgery is considered if you have osteoarthritis affecting just one compartment of their knee – the inner (medial) or outer (lateral) joint surface, or, very rarely, the kneecap. 

It is less invasive than total knee replacement surgery. This means that more of the original knee and its ligaments are preserved which has the benefit of retaining a more natural movement. 

Anyone who presents with arthritis is considered for this less invasive procedure, but, unfortunately, only a minority (10% to 15%) of my patients are actually found to be suitable. 

The deciding factors include your age and the exact distribution of arthritis. The best way to assess the situation is by either arthroscopy, either at the time of knee replacement surgery, or beforehand. MRI scan can also be a useful tool .

I favour the Oxford unicompartmental replacement. More details about it can be found here.

Oxford unicompartmental knee replacement
Total knee replacement

Frequently Asked Questions

5 nights.

You have no stitches to remove.

You will need to see a physiotherapist about once or twice a week for the first few weeks. If you don’t have a physiotherapist, please call Mr Sweetnam’s secretary who will recommend one in your area.

Two weeks post surgery.

After 6 weeks.

You can go back to work 6 weeks following surgery.