Unicompartmental Knee Replacement (UKR)
What is a UKR?
  • In cases where the arthritis is confined to one side of the knee then a unicompartmental (partial) knee replacement (arthroplasty) would be more suitable than a total knee replacement so as to preserve the unaffected parts of the knee
  • It involves taking away the arthritic joint surfaces on one side of the knee: 
    • Medial UKR (inside half): 
      • most commonly performed UKR as 70% of the forces through the knee go through this compartment 
      • therefore the medial knee compartment subjected to greater forces, friction and wear
    • Lateral UKR (outside half): 
      • Less commonly affected compartment so not performed as often
      • Patients having this operation report better outcomes than patients having a medial UKR which still has excellent results
Indications: when is it suitable?
  • Arthritis and symptoms are restricted to one side of the knee
Contraindications: when is it not suitable?
  • Inflammatory arthritis
  • Absence of ACL
  • Ligament instability
  • Contracted medial collateral ligament
  • Marked angular deformity to leg
  • Global knee pain
  • Marked arthritis in other parts of the knee
Expectations
  • Risks are very similar in nature to a  total knee replacement but they are slightly less severe and frequent as the operation is smaller and there is less trauma to the bones and tissues of the knee
  • Therefore rehabilitation is quicker and less painful
  • More than 90% of UKRs are still functioning after 10 years 
  • However, they are revised at slightly higher rate than total knee replacements because:
    • The arthritis may have spread to the other parts of the knee
    • Patients are higher functioning and do more high impact activities than patients with a TKR so wear out their implants quicker
    • They are easier to revise than a TKR
Advantages of a UKR vs TKR
  • Knee movement feels more natural as no ligaments cut and rest of knee preserved
  • Less disruption to tissues
  • Smaller incision (size of wound)
  • Less postoperative pain
  • Less bone removed
  • Less blood loss
  • Less risk of infection, bleeding and wound problems
  • Shorter stay in hospital
  • Quicker recovery
  • Easier, quicker, and fewer complications to revise in future 
  • Suitable for younger more physically active patients than for total knee replacements
Please see section on TKR for risks and complications and methods to minimise them.
Activities following UKR
  • The goal of the UKR is to allow a higher level of function than a TKR
  • However, to optimise the longevity of the implant below is a common sense approach to activities:
    • Recommended (low impact):
      • Walking
      • Cycling
      • Cross-trainer
      • Rowing
      • Swimming
      • Water aerobics
      • Dancing
      • Sedentary occupations (desk based)
    • Permitted (mild to moderate impact):
      • Gentle doubles tennis
      • Hiking
      • Light labour (occupations 
    • Avoid (high impact):
      • Jogging/running
      • Contact sports
      • Sports involving twisting/pivoting (basketball, competitive tennis, squash)
      • Heavy labour (involving heavy lifting, routinely using ladders, kneeling a lot)