A partial (unicompartmental) knee replacement replaces only the damaged part of the knee joint, preserving the healthy bone, cartilage, and ligaments. It is suitable when arthritis is limited to one compartment of the knee.
A smaller incision is made than for a total knee replacement. Only the damaged compartment (usually the inner/medial side) is resurfaced with a metal and plastic implant. The healthy parts of the knee, including the cruciate ligaments, are preserved. The operation typically takes one to one and a half hours.
A partial knee replacement is suitable when arthritis is confined to one compartment of the knee, the cruciate ligaments are intact, and the knee is not severely deformed. It may provide a more natural-feeling knee than a total replacement.
Weight management, physiotherapy, pain medication, activity modification, injections, and bracing. A total knee replacement is the main surgical alternative if the arthritis progresses or involves more than one compartment.
Standard pre-assessment. The same preparation as for total knee replacement.
Faster recovery, more natural knee movement, and preservation of bone stock compared to total knee replacement. Many patients report the knee feels more 'normal' than after a total replacement. Typically lasts 15–20 years.
Expected but often less than after total knee replacement.
The remaining compartments may develop arthritis over time, potentially requiring conversion to total knee replacement.
Common and usually settles.
The plastic bearing may dislocate in some designs. May require a further procedure.
Tibial plateau fracture is a rare but recognised complication.
If the partial replacement fails, conversion to a total knee replacement is needed. This is usually straightforward.
Risk similar to total knee replacement, approximately 1%.
DVT or pulmonary embolism despite preventive measures.
Spinal or general anaesthesia, as for total knee replacement.
Recovery is typically faster than total knee replacement. Hospital stay is one to two days. Many patients return to driving at three to four weeks and to desk work at similar timescales. Full recovery takes three to six months. Higher activity levels are often achievable than after total knee replacement.
Same schedule as total knee replacement.
A partial replacement preserves healthy bone and ligaments, gives a more natural feel, and allows faster recovery. However, it is only suitable if arthritis is limited to one compartment.
If the remaining compartments develop arthritis, the partial replacement can usually be converted to a total knee replacement.
Many surgeons are comfortable allowing higher activity levels with a partial replacement than with a total replacement, including gentle impact activities.