The Mark Coventry Award: in vivo knee forces during recreation and exercise after knee arthroplasty

Abstract

Knee forces directly affect arthroplasty component survivorship, wear of articular bearing surfaces, and integrity of the bone-implant interface. It is not known which activities generate forces within a range that is physiologically desirable but not high enough to jeopardize the survivorship of the prosthetic components. We implanted three patients with an instrumented tibial prosthesis and measured knee forces and moments in vivo during exercise and recreational activities. As expected, stationary bicycling generated low tibial forces, whereas jogging and tennis generated high peak forces. On the other hand, the golf swing generated unexpectedly high forces, especially in the leading knee. Exercise on the elliptical trainer generated lower forces than jogging but not lower than treadmill walking. These novel data allow for a more scientific approach to recommending activities after TKA. In addition, these data can be used to develop clinically relevant structural and tribologic testing, which may result in activity-specific knee designs such as a knee design more tolerant of golfing by optimizing the conflicting needs of increased rotational laxity and conformity.

Fig. 1

Postoperative radiograph of one of the subjects displays the location of the strain gauges (S), microprocessor (M), internal induction coil (C), and transmitting antenna.

Fig. 2

Peak forces were in the range of 1.8 to 2.5 times body weight (BW) for treadmill walking at the speeds tested. Treadmill speed during comfortable walking (range, 1–3 miles per hour) had no effect on peak tibial forces. A speed comparable to power walking (4 miles per hour) generated higher forces on the treadmill. Peak forces recorded during jogging were even higher than those recorded during power walking.

Fig. 3

Increasing the speed of bicycling from 60 to 90 rpm or increasing the resistance up to Level 3 did not substantially affect peak tibial forces. BW = body weight.

Fig 4A–B

High tibial forces were generated during the golf swing. (A) Much higher forces were generated in the leading knee relative to the trailing knee. (B) A golf swing with a driver tended to generate higher forces than a sand wedge. BW = body weight.

Fig. 5

Mean peak forces generated during the serve and during a forehand return were higher than those generated during the backhand return. BW = body weight.

Fig. 6A–B

(A) Exercising on the elliptical trainer generated mean peak tibial forces, which remained largely unchanged with increasing levels of difficulty. (B) Exercising on the StairMaster generated similar forces at low levels of intensity but increased to over 3 times body weight (BW) at higher levels.

Fig. 7A–B

(A) Peak tibial forces increased with increasing resistance during the leg-press activity but (B) did not change during the knee-extension activity. BW = body weight.