Home Consumer Info Conditions & Procedures Knee Joint Uniknee Replacement

Back to knee topics

Unicondylar (Unicompartmental) Knee Replacement

If only a single compartment of the knee is worn out, then it may be possible to
replace only the worn out component. This is usually done via a minimally invasive
approach and the recovery time is much quicker. A 7 to 10cm skin incision is used
and the kneecap is not reflected. The worn out surface is prepared. The femoral or
tibial component is usually glued or press-fitted in place. The patient can be mobilised
four to six hourly post-operatively and can go home after one to three days
depending on the amount of pain experienced.

In an arthritic knee

• The cartilage lining is thinner than normal or completely absent. The degree of
  cartilage damage and inflammation varies with the type and stage of arthritis.
• The capsule of the arthritic knee is swollen
• The joint space is narrowed and irregular in outline; this can be seen in an X-ray
  image.
• Bone spurs or excessive bone can also build up around the edges of the joint.

The combinations of these factors make the arthritic knee stiff and limit activities due to
pain or fatigue.

Diagnosis

• The diagnosis of osteoarthritis is made on history, physical examination & X-rays
• There is no blood test to diagnose Osteoarthritis (wear & tear arthritis)

Complications:

Anesthesia complications

As anybody undergoes general or regional anesthesia (epidural anesthesia) there
are always risks associated with it. The risks of course are magnified if you have
abnormal general medical conditions in addition to your older age, which may
have affected the functions of your vital organs such as heart, lungs and kidneys.
Therefore a complete evaluation of those systems has to be performed before you
are taken to the Operating theatre.

Specific complications relating to knee replacement surgery include the following:

1. Deep vein thrombosis: The risk of this occurring is lowered by giving blood thinning
   medication. However if it does occur more specific treatment is given.
2. Infection: The risk of infection is less than 1% and pre-operative antibiotics are
   given to prevent this from happening.
3. Stiffness: Occasionally knee replacement may stiffen up particularly in patients
   who are significantly overweight or have diabetes. Occasionally one will require
   a manipulation under an anaesthetic should this occur.
4. Nerve and vessel damage: It is unlikely that any major nerve or vessel will be damaged.
   It is, however, very common to have a small area of numbness over the outer side
   of your knee where a superficial skin nerve is always cut during the surgery.
   This little numb patch is of no significance.
5. Prosthesis failure: The prosthesis may fail due to the plastic wearing out and it
   may require revision.
6. Reflex sympathetic dystrophy: Very rarely a condition can occur where the leg becomes
   stiff, hypersensitive and painful. This requires specific treatment with a pain management specialist.
7. Excessive bleeding around the joint: This usually settles but may require drainage.
8. Excessive scarring: Some skin will scar up significantly (keloid).
9. Fluid build-up in the knee joint: Occasionally this may occur and require drainage.
   It is usual for knees to be a little swollen and a little warm.
10. Pain with kneeling: Kneeling may produce discomfort over the incision site.

Patello-femoral replacement:

If the patello-femoral joint is the only part that is worn out, then this can be replaced
similarly to a uni-compartmental knee replacement. The incision is similar to a total knee replacement but naturally less bone is removed. A total knee replacement may be
required in the future.