Patella Tracking and Kinematic Assessment for Knee Arthroplasty

Patellofemoral joint biomechanics profoundly influence knee replacement outcomes. Howmedica Osteonics presents a surgical method that tracks the patella‘s position and movement through knee flexion and extension, generates a kinematic profile of how the patella naturally moves, and compares this profile to target parameters. Surgeons can then decide whether to preserve the native patella or modify technique based on kinematic assessment.

The Problem

Proper patellar function after total knee arthroplasty remains challenging. The patella must track correctly through the femoral groove during knee flexion and extension, maintaining appropriate load distribution and avoiding edge-loading that causes pain and accelerates wear. Traditional surgical techniques do not systematically assess patellofemoral kinematics before and after bone resections, leaving surgeons to make intra-operative decisions with limited objective information about patellar movement.

Patellofemoral joint assessment proves particularly difficult during surgery because the joint’s complex three-dimensional kinematics are not visible to the surgeon without specialized imaging. Determining whether native patellar anatomy will function adequately with the planned implants requires intra-operative kinematic evaluation that current practice does not systematically provide. Surgeons must estimate patellar function based on visual inspection and experience rather than objective kinematic data. This lack of objective assessment contributes to variable outcomes and occasional patellofemoral complications.

What This Invention Does

Howmedica’s method initiates by tracking a point on or adjacent to the unresected patella as the knee moves through flexion and extension. This tracking establishes the native kinematic profile – the actual path the patella follows during knee motion. The system displays and compares this native profile against a target kinematic profile that represents ideal patellar tracking. The native profile generates quantitative kinematic data that reveals whether the patella naturally tracks within safe zones during knee motion.

If the native kinematics fall within predetermined safe thresholds relative to the target profile, surgeons may proceed with standard resection protocols, preserving the patient’s natural patellar anatomy. If native kinematics fall outside safe zones, surgeons implement pre-resection steps to modify bone cuts or implant positioning before creating irreversible bone resections. This objective kinematic assessment replaces estimation with quantitative data, enabling evidence-based surgical decisions about patellar preservation versus modification.

Key Features

• Native Patella Tracking Measurement. The system precisely captures patellar position and movement throughout the knee’s range of motion, generating detailed kinematic profiles of natural patella behavior.
• Kinematic Profile Generation. Tracking data is processed into a comprehensive profile showing how the patella moves relative to the femoral implant throughout flexion and extension.
• Target Comparison Framework. The native kinematic profile is systematically compared to predetermined target profiles that represent optimal patellar tracking characteristics.
• Safe Zone Definition. Predetermined thresholds establish acceptable ranges for patellar tracking, allowing surgeons to determine whether native anatomy aligns with desired characteristics.
• Intra-operative Assessment. The measurement and comparison process occurs during surgery, enabling real-time decision-making about bone resections and implant positioning before they are executed.
• Pre-resection Modification Guidance. When native kinematics fall outside safe zones, the system guides surgeons on modifications to implement before bone cutting, enabling anatomy-specific optimization.
• Kinematic Profile Preservation Option. The system identifies patients whose natural patellar kinematics align with targets, enabling preservation of native anatomy when appropriate.

Who Is Behind It?

Howmedica Osteonics Corp., headquartered in the United States, specializes in orthopedic surgical implants and instruments. The invention credits three inventors: Emily Hampp, Azhar Ali, and Sebastien Lustig, representing the company’s surgical innovation and kinematic analysis expertise. The application prioritizes US Patent Application 63/688,017, filed 28 August 2024. IP Gateway Patent and Trade Mark Attorneys provides representation, supporting IP protection strategy.

Why It Matters

Patellofemoral complications represent a significant source of patient dissatisfaction following knee arthroplasty. This innovation provides surgeons with objective kinematic data to guide surgical decisions about patellar management. The ability to assess native patellar kinematics intra-operatively and compare to target profiles represents a substantial advancement over visual estimation alone. The system supports a more conservative approach for patients whose native anatomy aligns with optimal kinematics, potentially reducing surgical modification while improving outcomes. For patients whose anatomy requires modification, the system guides surgeons on specific adjustments needed before irreversible bone cuts. This kinematic assessment methodology could be adapted to other joints, establishing a broader paradigm of objective kinematic guidance in arthroplasty surgery.

Related Concepts

Total knee arthroplasty is one of the most commonly performed orthopaedic procedures worldwide. While implant survivorship now routinely exceeds 15 years, patient satisfaction remains variable, with patellofemoral complications – including maltracking of the kneecap – among the leading causes of revision surgery and persistent pain.

The patella glides within the femoral trochlear groove through the full arc of knee flexion and extension. Its path – influenced by implant geometry, soft tissue tension, and bony anatomy – must remain centred to avoid edge-loading and lateral instability. Intraoperative kinematic tracking gives surgeons objective data to guide these critical surgical decisions before irreversible bone cuts are made.

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AU 2025220734 was published in the Australian Official Journal of Patents on 19 March 2026 and is open for public inspection. Patent applications represent inventions that are sought to be protected and do not necessarily reflect commercially available products.