Locking Total Knee Replacement Design for Treating Knee Extensor Weakness

Market Overview:

This design allows patients to selectively lock the knee in full extension for the purposes of ambulation and unlock free rotation when desired. According to the American Academy of Orthopedic Surgeons, over 600,000 total knee replacement surgeries are performed in the United States each year. While total knee replacement (TKR) is a definitive method to restore knee function in most patients, some have trouble with knee function and weakness following surgery. Knee arthrodesis is required when a patient has inadequate muscular control or soft tissue stability to ambulate. This extended position requires greater muscular strength and endurance to control, even when sitting, which leads to secondary joint pain and muscular fatigue. The permanence of such a position can also prevent patient participation in many activities of daily living. Clemson University researchers developed a new design that provides an alternative surgical treatment to arthrodesis. This design enables a patient controlled locking mechanism within a TKR that can allow for bending of the knee joint when necessary.  This provides functional convenience for patients, allowing them to flex their knee joint as necessary during passive functions and to walk with the functional equivalence of arthrodesis.

Application                                                                                                         Stage of Development

Reconstructive knee surgery; Alternative treatment to arthrodesis                     Validated Prototype


• TKR variant with a non-invasive, handheld, user controlled extension lock, addressing knee dysfunction and arthrodesis complications

• Modular design to fit in existing platform TKR designs, providing simple incorporation of new technology

• Ability to lock the knee in extension, reducing the magnitude of the compressive joint reaction force and resulting in near-complete reduction of quadriceps forces

Technical Summary

The proposed design is a variant of a stabilized total knee replacement used for reconstructive surgery. The device is predicated on hinged knee designs, but incorporates novel features that allow the user to selectively activate and deactivate a latch that locks the device in a position of full extension. The latch incorporates magnets, which allow the user to actuate the latch using an externally applied magnetic field, such as a handheld magnet. The latch is robust enough to resist bending at physiologically relevant loads. This allows the user to walk with a stiff leg gait when the device is locked in full extension. When the user unlocks the device, the user is able to flex the knee as desired or necessary. This reduces the movement of the leg when sitting or lying, increases mobility, and eliminates pain secondary to knee fusion, ultimately solving the problem of terminal knee extensor mechanism weaknesses that traditionally prevent patients from ambulating.

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Inventors:                        Eric Lucas, John DesJardins, Kim Chillag, Frank Voss

Application Type:           Utility

Patent Number:              9,072,606; 9,393,123; 9,693,867

CURF Reference:           2012-084

Patent Information:
Biomedical Sciences
For Information, Contact:
Chase Kasper
Business Development
Clemson University Research Foundation
Eric Lucas
John DesJardins
Kim Chillag
Frank Voss
Medical Device
Orthopaedics - Orthotics/Prosthetics/Hardware/Other
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