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Uni-compartamental Knee Replacement

Uni-compartmental knee replacement is an operation in which only the damaged compartment of the knee is replaced with an implant. It is also called a partial knee replacement. The knee can be divided into three compartments: patellofemoral, the compartment in front of the knee between the knee cap and thigh bone, medial compartment, on the inside portion of the knee, and lateral compartment which is the area on the outside portion of the knee joint.Uni-compartamental replacements usually refers to the inner or outer side of the knee and not the patella femoral joint. Your surgeon may recommend surgery if non-surgical treatment options such as medications, injections and physical therapy have failed to relieve the symptoms.

Selection criteria

There are specific criteria required for a patient to be suitable for a uni-compartamental knee replacement (Over and above the usual total joint replacement contraindications)

  • Only one compartment affected by arthritis (minor painless patella femoral arthritis is not a contral-indication)
  • Stable knee with intact cruciate and collateral ligaments
  • Good range of movement (no more than 10 degree fixed bend and bending past 100 degrees)
  • Non inflammatory arthritis (no Rheumatoid type arthritis)
  • Non Obese patients
  • Pain limited to the arthritic compartment
  • No extreme angular deformity


  • Under anaesthesia, with of without a tourniquet
  • An modest incision is made over the knee to expose the knee joint
  • The knee is inspected for the appropriateness of the partial knee replacement
  • Only the damaged side of the joint is prepared, removing the meniscus and shaping the tibial and the femur to receive the appropriate sized implants
  • Accurate cuts are made with special instruments. On occasion, computer navigation may aid in assessing alignment
  • The knee is checked for balance, alignment,stability and range of movement
  • The implants may be cemented or un-cemented
  • The wound is closed in layers

Goals and outcome

The aim of the surgery is to reduce pain in the knee, to re-align or straighten the knee and to regain functional or near normal range of movement. Restore a good quality of life. The long term results following partial knee replacement are good and recent results equivalent with those for total knee replacement surgery.

As part of the preparation for surgery, the better informed and prepared the patient is, the better the likely outcome. Signing an informed consent is a vital part of preparing for surgery. Attending a preadmission clinic is helpful. Many steps and actions are taken to reduce the risks of surgery and to aid in an uneventful full post-operative recovery.

The advantages of this form of knee replacement surgery may be:

  • Less soft tissue and bony dissection and resection allows for faster recovery
  • Shorter hospital stay
  • Reduced blood loss
  • Less pain and lower dose analgesia required
  • A better range of movement compared to TKR
  • A more natural feeling knee

Post-Operative care

Post-operative pathway usually include:

  • The patient beingmonitored regularly
  • Pain will be managed in a multi-modality style
  • Drugs will be administered to avoid blood clots, prevent infections and prevent bleeding
  • Urinary catheters usually remain in for 1-2 days
  • Patients usually stay 3-4 days in the acute care ward
  • Patients will be given specific instructions regarding exercises and activity. Starting on the day of surgery. The physiotherapist will guide these
  • Knee and leg swelling is common after knee surgery. Ice and elevation of the leg are recommended to minimize swelling and pain
  • Foot or calf pumps, early mobilising and hydration will be utilised to prevent calf and lung clots
  • If progress is slow, a referred to in or out patient rehabilitation will be arranged
  • Eating a healthy diet and not smoking will promote healing

Risks and complications

As with any major surgery, possible risks and complications associated with uni-compartamentalknee replacement surgery include, but are not limited to:

  • Progression of arthritis in the untreated parts of the joint with pain
  • Knee pain
  • Wound breakdown and oozing
  • Knee stiffness
  • Infection, superficial and deep
  • Blood clots (deep vein thrombosis, pulmonary embolus)
  • Fractures around the knee joint
  • Nerve and blood vessel damage
  • Numbness around the scar
  • Instability
  • Clicking
  • Patella (kneecap) dislocation
  • Plastic liner wears out
  • Loosening of the implant
  • Bone loss from wear debris

The patient is a very important part of the pathway pre and post surgery. Patients need to be responsible for there own health and follow instructions. Informing the doctor or appropriate professional if there is a concern. Early diagnosis and treatment of complications will improve the success of treatment.

Uni-compartamental Knee Replacement