Diminished Knee Reflex Following Total Knee Arthroplasty

Mechanism and Clinical Implications

The American College of Radiology suggests that the altered knee anatomy following TKA affects the normal biomechanics of the knee joint and the function of the extensor mechanism, which may contribute to changes in reflex response 1, 2
Component positioning and rotation can affect patellar alignment and tracking, which may contribute to changes in reflex response, according to the American College of Radiology 1, 2
Patellofemoral instability occurs in 1-12% of TKA patients, often due to internal malrotation of femoral and/or tibial components, which may further impact reflex mechanisms, as reported by the American College of Radiology 1
Extensor mechanism alterations following TKA can include changes to the quadriceps and patellar tendons, potentially affecting the reflex arc, as noted by the American College of Radiology 3

The American College of Radiology states that the most common complications following TKA include loosening (39.9%), infection (27.4%), instability (7.5%), periprosthetic fracture (4.7%), and arthrofibrosis (4.5%) 4
Patellar complications occur in approximately 3.6% of TKA cases and include subluxation, dislocation, fracture, component loosening or wear, impingement, and osteonecrosis, according to the American College of Radiology 5

The American College of Radiology recommends that radiographs remain the initial imaging modality for evaluation of a patient with TKA concerns, typically consisting of anteroposterior, lateral, and axial views 4
CT is the modality most commonly used for measuring axial malrotation of knee prosthesis components when alignment issues are suspected, as reported by the American College of Radiology 6
MRI with metal artifact reduction techniques can be used to assess soft tissue complications and component rotation, according to the American College of Radiology 3