Tibiofemoral Cartilage Contact Differences Between Level Walking and Downhill Running.

Background: Some studies have suggested that altered tibiofemoral cartilage contact behavior (arthrokinematics) may contribute to long-term cartilage degeneration, potentially leading to tibiofemoral osteoarthritis. However, few studies have assessed normal tibiofemoral arthrokinematics during dynamic activities. Purpose: To characterize tibiofemoral arthrokinematics during the impact phase of level walking and downhill running. Study Design: Descriptive laboratory study. Methods: Arthrokinematic data were collected on uninjured knees of 44 participants (mean age, 20.7 +/- 6.6 years). Using a dynamic stereoradiographic imaging system with superimposed 3-dimensional bone models from computed tomography and magnetic resonance imaging of participant-specific tibiofemoral joints, arthrokinematics were assessed during the first 15% of the gait cycle during level walking and the first 10% of the gait cycle during downhill running. Results: During level walking and downhill running, the medial compartment had a greater cartilage contact area versus the lateral compartment. Both compartments had a significantly less cartilage contact area during running versus walking (medial compartment gait cycle affected: 8%-10%; lateral compartment gait cycle affected: 5%-10%). Further, medial and lateral compartment tibiofemoral contact paths were significantly more posterior and longer during downhill running. Conclusion: There was a decreased tibiofemoral cartilage contact area during downhill running compared with level walking, suggesting that underlying bone morphology may play a key role in determining the size of cartilage contact regions.