Expert perspective from Richard Scott, who performed his first UKA in 1973, synthesizing 50 years of lessons on patient selection, implant design, alignment, and technique. The paper traces the evolution from the original Kozinn-Scott criteria through the 2015 liberalized consensus and distills the technical principles that determine UKA success or failure.
UKA sits at a decision crossroads every time you see a patient with isolated medial compartment arthritis. The 1%/year failure rate (versus 0.3–0.5%/year for TKA) is the number you quote when counseling patients — but the faster recovery, cruciate preservation, and easier revision tip the balance for the right candidate.
When selecting patients, apply the Kozinn-Scott framework: varus <10°, intact ACL without subluxation, flexion contracture <15°, and patellofemoral arthritis no worse than grade 3. The 2015 liberalized criteria let you offer UKA to obese patients (with a metal-backed tibial component) and younger patients (with conservative tibial resection), expanding your candidate pool from 6% to roughly 10–15% of arthroplasty patients.
Intraoperatively, two technical rules are non-negotiable: use a non-conforming (round-on-flat) bearing for any fixed-bearing construct, and target 2–5° anatomic valgus without performing a formal medial release. Overcorrection and conforming fixed bearings are the two most avoidable causes of early failure.
For lateral UKA, always use a medial parapatellar approach. A mini-lateral incision locks you out of intraoperative TKA conversion if needed.
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Expert perspective from Richard Scott, who performed his first UKA in 1973, synthesizing 50 years of lessons on patient selection, implant design, alignment, and technique. The paper traces the evolution from the original Kozinn-Scott criteria through the 2015 liberalized consensus and distills the technical principles that determine UKA success or failure.
UKA sits at a decision crossroads every time you see a patient with isolated medial compartment arthritis. The 1%/year failure rate (versus 0.3–0.5%/year for TKA) is the number you quote when counseling patients — but the faster recovery, cruciate preservation, and easier revision tip the balance for the right candidate.
When selecting patients, apply the Kozinn-Scott framework: varus <10°, intact ACL without subluxation, flexion contracture <15°, and patellofemoral arthritis no worse than grade 3. The 2015 liberalized criteria let you offer UKA to obese patients (with a metal-backed tibial component) and younger patients (with conservative tibial resection), expanding your candidate pool from 6% to roughly 10–15% of arthroplasty patients.
Intraoperatively, two technical rules are non-negotiable: use a non-conforming (round-on-flat) bearing for any fixed-bearing construct, and target 2–5° anatomic valgus without performing a formal medial release. Overcorrection and conforming fixed bearings are the two most avoidable causes of early failure.
For lateral UKA, always use a medial parapatellar approach. A mini-lateral incision locks you out of intraoperative TKA conversion if needed.