Robotic arm assisted Patello-femoral Joint Replacement

What is it?

Patello-femoral joint replacement is performed for arthritis that solely affects the patello-femoral joint (kneecap joint).

The patello-femoral joint is made up of the patella (kneecap) and the end of the thighbone (femur) that articulates with the patella the trochlea.

Arthritis can affect both or only one of the patella and the trochlea. Normally, the joint surfaces are covered by a smooth, frictionless surface called articular cartilage. When this wears away, the joint surfaces become rough causing pain usually felt at the front of the knee, swelling, restriction in movement and function and stiffness.

This procedure replaces the worn surfaces of the joint with artificial surfaces, and in doing so, relieves pain, swelling and stiffness, improves range of movement and function.

This procedure is relatively new, when compared with total knee replacement for example. Designs of patello- femoral replacements are constantly evolving and Mr Patel will be happy to talk to you about suitable implants at your consultation. With the advent of robotic arm assisted surgery (Stryker - MAKO), patellofemoral joint replacement has been revolutionised by facilitating a degree of accuracy and personalisation that is unprecedented and results in better outcomes.

Who should have patello-femoral joint replacement?

Patello-femoral joint arthritis causes anterior (front) knee pain that is worse going up and down stairs or inclines. It may also cause pain at night, like arthritis of any joint, and when severe, cause pain at rest.

Initial treatment is almost always involves strengthening exercises, weight loss, analgesia, joint supplements and cortisone injections. Most patello- femoral conditions resolve with this treatment.

When these become less effective and quality of life begins to deteriorate, one may consider surgery. This may be in the form of knee arthroscopy, which aims to assess the extent of the arthritis, stabilise any cartilage lesions and lavage the joint of any debris; the results of this can provide temporary relief, but cannot reverse or cure the arthritic process. If arthroscopy is unsuccessful, and quality of life continues to be poor, the next surgical option is replacement.

The decision to undergo surgery should be discussed in detail with Mr Patel at your consultation.

Will I need any tests/scans?

X-rays and a CT scan will be requested for all cases. MRI can be used to ensure that other parts of the joint are not affected by arthritis, or in some circumstances, a diagnostic knee arthroscopy may be performed to accurately assess the joint. Please see the section Surgery FAQs to see if you will need any other tests e.g. blood tests before your surgery.

How is it done?

The surgery is usually carried out under general anaesthetic. A tourniquet is applied and inflated. The incision is made at the front of your knee, in the midline. The robotic arm assists in removing worn areas of the joint and then the implant is fixed into place, usually using special bone cement. The implant is essentially made up of two metal alloy parts and a polyethylene (high grade plastic) insert. The movement and stability of the joint are checked.

The wound is closed with sutures and clips and a small drain is inserted to help remove excess fluid in the first 24-48 hours. A dressing and bandage are then applied.

The procedure normally takes between 1-2 hours.

How long is the hospital stay?

Your stay in hospital will approximately be between 3-7 days. Safely regaining mobility with crutches and being able to go up and down stairs are pre- requisites for discharge. Post-operatively, a blood test and an X-ray will be taken. The drain will be removed on the ward.

What about after I leave hospital?

You will see a physiotherapist before discharge to be instructed on crutch use and simple exercises to carry out in the short term. Crutches are advised for approximately 4-6 weeks, but this varies from patient to patient.

You will be allowed to weight-bear as tolerated in most cases. Swelling of the knee and lower leg and bruising is very common after patello-femoral joint replacement and is to be expected. It may persist for several weeks until full range of motion and mobility has been regained.

You will be prescribed analgesia to take home and Mr Patel strongly advocates its use to keep pain to a minimum; it should be noted that pain is more difficult to control if it is allowed to establish itself. Mr Patel recommends the regular application of ice as an adjunct to relieve pain and swelling in the acute post-operative period.

You will also be prescribed anti-coagulant medication to take for a further 14 days or until you are fully mobile. This is to minimise the risk of a deep vein thrombosis.

You will see Mr Patel two weeks after surgery for a wound check (and stitch/clip removal) and a physiotherapy program will ensue thereafter which is paramount to the success of the operation. You are likely to have been seeing a physiotherapist before the operation and Mr Patel will liaise with him/her in detail to advise on the post-operative exercise program.

Total recovery time is between 3-6 months. Gradual improvement is seen during this period and Mr Patel advises driving can resume once he has seen you and consented.

It is good and common practice to keep patello-femoral joint replacements under regular review to ensure they are performing adequately. Thus routine follow up should be organised. Mr Patel would like to see you for clinical examination and X-ray your knee at the following post-operative intervals:

  • 6 weeks (no X-ray required)
  • 6 months
  • 1 year
  • 2 year
  • 5 years
  • 10 years
  • Every 5 years after that

What are the potential complications?

All surgery carries a risk. Specific risks to patello-femoral joint replacement are:

Infection this can be either superficial (wound) or within the joint. Antibiotics will be given to reduce this risk.

Thrombosis a clot in the deep veins of the lower limb (DVT). The risk is minimised by early mobility and anti-coagulant medication. Oral contraceptive pills and HRT, which are known to increase risk, should be stopped before surgery. Mr Patel will advise you on this

Bleeding this may require a return to the operating room for removal of blood clots and to stop the bleeding.

Stiffness It is very important that some mobility of the knee is maintained after surgery. The physiotherapist will advise on simple exercises that can be carried out at home. Mr Patel also recommends that you take regular analgesia and use ice (see Surgery FAQs) to help minimise post- operative discomfort and facilitate early movements.

Loosening the implant can become loose, either due to infection or as a function of time. It will need to be replaced in either case.

Residual symptoms unfortunately, no guarantees can be offered regarding curing your symptoms, despite the surgeon’s best efforts. In this case, further management and treatment options will be discussed with you.

For private patients

The Wellington Hospital
The Knee Unit
Wellington Place
London NW8 9LE

Tel: 02074835059
Fax: 020 7483 9131
PA Email:

The Schoen Clinic
66 Wigmore Street
London W1U 2SB

Tel: 02074835059
PA Email:

For NHS patients

University College London Hospital
2nd Floor Maple House
149 Tottenham Court Road
London W1T 7BN

Tel: 02034479413
Fax: 020 7380 9081
PA Email: