Knee Joint Loading during Single-Leg Forward Hopping

Increased or abnormal loading on the intact limb is thought to contribute to the relatively high risk of knee osteoarthritis in this limb for individuals with unilateral lower limb loss. This theory has been assessed previously by studying walking, but knee joint loading during walking is often similar between individuals with and without limb loss, prompting assessment of other movements that may place unusual loads on the knee. One such movement, hopping, is a form of locomotion that individuals with unilateral lower limb loss may situationally use instead of walking, but the mechanical effects of hopping on the intact limb are unknown. Purpose: Compare knee joint kinetics of healthy adults during single-leg forward hopping compared to walking, a more traditional form of locomotion. Methods: Twenty-four healthy adults walked and hopped at self-selected speeds of 1.5 and 2.3 m.s(-1), respectively. Joint moments were calculated using inverse dynamics. A paired Student's t-test was utilized to compare peak, impulse, and loading rate (LR) of knee adduction moment (KAM), and peak knee flexion moment (KFM) between walking and hopping. Results: Peak KFM and KAM LR were greater during hopping compared to walking (peak KFM: 20.73% vs 5.51% body weight (BW) x height (Ht), P < 0.001; KAM LR: 0.47 vs. 0.33 BW.Ht.s(-1), P = 0.01). Conclusions: Kinetic measures affecting knee joint loading are greater in hopping compared to walking. It may be advisable to limit single-leg forward hopping in the limb loss population until it is known if these loads increase knee osteoarthritis risk.