In vivo knee loading characteristics during activities of daily living as measured by an instrumented total knee replacement

Abstract

We examined the relationship between activity, peak load, medial to lateral load distribution, and flexion angle at peak load for activities of daily living. An instrumented knee prosthesis was used to measure knee joint force simultaneously with motion capture during walking, chair sit to stand and stand to sit, stair ascending and descending, squatting from a standing position, and golf swings. The maximum total compressive load at the knee was highest during stair ascending and descending and lowest during rising from a chair. Maximum total compressive load occurred at substantially different flexion angles ranging from 8.58 during walking to 91.88 during squatting. For all activities, total compressive load exceeded 2 times body weight, and for most activities 2.5 times body weight. Most activities placed a greater load on the medial compartment than the lateral compartment. Activities were grouped into three categories: high cycle loading (walk), high load (stair ascent, descent, and golf), and high flexion angle (chair sit to stand/stand to sit, and squat). The results demonstrate that the forces and motion sustained by the knee are highly activity-dependent and that the unique loading characteristics for specific activities should be considered for the design of functional and robust total knee replacements, as well as for rehabilitation programs for patients with knee osteoarthritis or following total knee arthroplasty. Keywords: contact force; ambulation; total knee replacement; arthroplasty; wearThe anatomy of the human knee is complex, and the knee is able to sustain large contact forces over a broad range of flexion angles. The tibial-femoral motion is related to the activity, the phase of the activity, and flexion angle.1,2 Similarly, the magnitude of contact force varies between activities and between the phases of the activity. 3 The relationships among flexion angle, peak joint loading, and the balance of medial to lateral load distribution for different activities can provide important insight for understanding normal and pathological conditions.The human knee experiences flexion angles from 08 to 308 during the stance phase of normal walking and from 308 to 608 during the swing phase of normal walking. Similarly, the load on the knee varies greatly between the stance and swing phase with loads exceeding two times body weight during stance.3 The knee adduction moment as a marker for the medial to lateral load distribution has been related to the ratio of medial to lateral cartilage thickness. 4 Regions of frequent loading, i.e., regions that are in contact over the range of flexion angles during walking, have thicker cartilage, and regions that are less likely to be loaded have thinner cartilage. 4 Therefore, not only the load magnitude seems to be an important determinant of ambulatory mechanics, but also the flexion angle at which these loads occur. The relationship between loads and flexion angle is also important for nonambulatory activities. For instance, the incidence of knee ost...

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