KRO · Class II · 21 CFR 888.3510

FDA Product Code KRO: Prosthesis, Knee, Femorotibial, Constrained, Cemented, Metal/polymer

Constrained knee designs address the most challenging revision and deformity cases in orthopedic surgery. FDA product code KRO covers constrained cemented femorotibial knee prostheses.

These implants provide mechanical constraint of varus-valgus and rotational motion through a linked hinge or post-cam mechanism, compensating for severe ligamentous insufficiency that cannot be managed with less constrained designs.

KRO devices are Class II medical devices, regulated under 21 CFR 888.3510 and reviewed by the FDA Orthopedic panel.

Leading manufacturers include Howmedica Osteonics Corp., Biomet, Inc. and Zimmer, Inc..

86
Total
86
Cleared
121d
Avg days
1979
Since
Declining activity - 4 submissions in the last 2 years vs 6 in the prior period
Review times improving: avg 60d recently vs 124d historically

FDA 510(k) Cleared Prosthesis, Knee, Femorotibial, Constrained, Cemented, Metal/polymer Devices (Product Code KRO)

86 devices
1–24 of 86
Cleared Dec 15, 2025
Triathlon® Tritanium® Asymmetric Patella
K252898
Howmedica Osteonics Corp., Dba Stryker Orthopaedics
Orthopedic · 95d
Cleared Aug 22, 2025
Stem Extension Line (USTAR II System)
K252303
United Orthopedic Corporation
Orthopedic · 29d
Cleared Jul 25, 2025
Triathlon® Hinge Knee System
K251665
Howmedica Osteonics Corp., Dba Stryker Orthopaedics
Orthopedic · 56d
Cleared Nov 21, 2024
ATTUNE™ Revision Hinge Knee
K242871
Depuy Ireland UC
Orthopedic · 59d
Cleared Apr 01, 2024
EVOLUTION® Hinge Knee System
K240043
Microport Orthopedics, Inc.
Orthopedic · 87d
Cleared Mar 21, 2024
ATTUNE Total Knee System, ATTUNE Cementless Knee System, LPS Limb Preservation System, Sigma High Performance (HP) Partial Knee System
K233980
Depuy Ireland UC
Orthopedic · 94d
Cleared Sep 27, 2023
EVOLUTION® Hinge Knee System
K230563
Microport Orthopedics, Inc.
Orthopedic · 210d
Cleared May 19, 2023
Triathlon® Hinge Knee System
K230416
Stryker
Orthopedic · 92d
Cleared Apr 21, 2023
Modular Rotating Hinge Knee Systems and Compatible Components
K223069
Howmedica Osteonics Corp., Dba Stryker Orthopaedics
Orthopedic · 203d
Cleared Jan 20, 2023
Triathlon® Hinge Knee System
K223528
Howmedica Osteonics Corp., Dba Stryker Orthopaedics
Orthopedic · 58d
Cleared May 03, 2022
LINK Endo-Model EVO Knee System
K220628
Waldemar Link GmbH & Co. KG
Orthopedic · 60d
Cleared Jul 28, 2021
ELEOS Limb Salvage System
K211677
Onkos Surgical
Orthopedic · 57d
Cleared Jun 30, 2021
LINK Endo-Model Knee System, Femoral Segments (Augments), UHMWPE
K211768
Waldemar Link GmbH & Co. KG
Orthopedic · 22d
Cleared Mar 02, 2021
GMK Revision & Hinge Extension - TiNbN Coating
K210010
Medacta International S.A.
Orthopedic · 57d
Cleared Dec 10, 2020
Zimmer Segmental System
K192798
Zimmer, Inc.
Orthopedic · 437d
Cleared Oct 25, 2019
Instruments for LINK MEGASYSTEM-C Family
K190181
LinkBio Corp.
Orthopedic · 266d
Cleared Oct 08, 2019
Attune Revision LPS Inserts
K191779
Depuy(Ireland)
Orthopedic · 98d
Cleared Sep 23, 2019
USTAR II System
K190100
United Orthopedic Corporation
Orthopedic · 244d
Cleared Nov 01, 2017
GMK Hinge, GMK Revision
K172347
Medacta International S.A.
Orthopedic · 90d
Cleared Feb 06, 2015
Zimmer Segmental System XT Components
K150028
Zimmer, Inc.
Orthopedic · 30d
Cleared Feb 22, 2013
DISTAL FEMORAL GROWING PROSTHESIS, TIBIAL ROTATING COMPONENTS, BEARING, AXIS, CIRCLIP, WEDGE
K122015
Howmedica Osteonics Corp.
Orthopedic · 227d
Cleared Jul 01, 2011
ZIMMER SEGMENT SYSTEM TRABECULAR METAL PROXIMAL TIBIAL COMPONENT, TRABECULAR METAL PROXIMAL COMPONENT, ADDITIONAL SEGMEN
K110940
Zimmer, Inc.
Orthopedic · 88d
Cleared Jul 23, 2008
LEGION HINGE KNEE SYSTEM
K081111
Smith & Nephew, Inc.
Orthopedic · 96d
Cleared Jun 11, 2008
SEGMENTAL DISTAL FEMORAL COMPONENTS AND PROXIMAL FEMORAL BODIES WITH A COMPRESS FEMALE TAPER
K080330
Biomet, Inc.
Orthopedic · 126d

About Product Code KRO - Regulatory Context

510(k) Submission Activity

86 total 510(k) submissions under product code KRO since 1979, with 86 receiving FDA clearance (average review time: 121 days).

Submission volume has declined in recent years - 4 submissions in the last 24 months compared to 6 in the prior period.

FDA 510(k) Review Time - KRO Product Code

Recent submissions under KRO have taken an average of 60 days to reach a decision - down from 124 days historically, suggesting improved FDA processing for this classification.

KRO devices are reviewed by the Orthopedic panel. Browse all Orthopedic devices →