Loading of the knee joint during ergometer cycling: telemetric in vivo data.

STUDY DESIGN: Within-subject, repeated-measures design.

OBJECTIVES: To measure tibiofemoral contact forces during cycling in vivo and to quantify the influences of power, pedaling cadence, and seat height on tibiofemoral contact forces.

BACKGROUND: Cycling is usually classified as a low-demand activity for the knee joint and is therefore recommended for persons with osteoarthritis and rehabilitation programs following knee surgery. However, there are limited data regarding actual joint loading.

METHODS: Instrumented knee implants with telemetric data transmission were used to measure the tibiofemoral contact forces. Data were obtained in 9 subjects, during ergometer cycling and walking, 15 ± 7 months after total knee arthroplasty. Tibiofemoral forces during cycling at power levels between 25 and 120 W, cadences of 40 and 60 rpm, and 2 seat heights were investigated.

RESULTS: Within the examined power range, tibiofemoral forces during cycling were smaller than those during walking. At the moderate condition of 60 W and 40 rpm, peak resultant forces of 119% of body weight were measured during the pedal downstroke. Shear forces ranged from 5% to 7% of body weight. Forces increased linearly with cycling power. Higher cadences led to smaller forces. A lower seat height did not increase the resultant force but caused higher posterior shear forces.

CONCLUSION: Due to the relatively small tibiofemoral forces, cycling with moderate power levels is suited for individuals with osteoarthritis and rehabilitation programs following knee surgery, such as cartilage repair or total knee replacement. The lowest forces can be expected while cycling at a low power level, a high cadence, and a high seat height.