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Partial (Unicompartmental) Knee Replacement
The knee joint has three main compartments; inner, outer, and behind the kneecap, and osteoarthritis often affects one more severely than the others.
A partial, or unicompartmental, knee replacement replaces only the damaged compartment, leaving the healthy parts of the knee, including the natural ligaments, intact.
Understanding the Surgery
Knee prior to surgery
Osteoarthritis with cartilage loss isolated to inside of the knee (medial)
A partial knee replacement implant on the inside of the knee preserving the soft tissues
Knee seen following surgery with the scar slightly to the medial side
Who's a Good Candidate
Good candidates typically have arthritis genuinely confined to a single compartment, with the rest of the knee - including the cruciate ligaments - in reasonably good condition. It's generally not suitable for more widespread, multi-compartment arthritis, significant deformity, or ligament instability.
Careful assessment and imaging confirm exactly which compartments are affected before this option is considered.
A more natural feel — with the healthy ligaments and bone preserved, movement can feel
more like your own knee than a total replacement
Less invasive surgery — typically a smaller incision, less blood loss, and for many patients,
a somewhat quicker initial recovery
Faster return to activity — many patients regain mobility a little sooner in the first few
weeks compared with total knee replacement
Benefits Over a Total Knee Replacement
A partial knee replacement doesn't address arthritis in other compartments, so if arthritis progresses elsewhere in the knee, a total knee replacement may become necessary later.
Long-term data has historically shown a somewhat higher revision rate than total knee replacement, though outcomes have improved with modern implants and technique. This is discussed openly as part of your decision-making.
Considerations
The Role of Robotic-Assisted Planning
Robotic-assisted planning can be particularly valuable for partial knee replacement, since precise implant positioning matters significantly for how well the replaced compartment works alongside the knee's remaining natural structures. Read more about robotic-assisted knee replacement.