Ambulation speed and corresponding mechanics are associated with changes in serum cartilage oligomeric matrix protein

Because serum cartilage oligomeric matrix protein (COMP) has been used to reflect articular cartilage condition, we aimed to identify walking and running mechanics that are associated with changes in serum COMP. Eighteen subjects (9 male, 9 female; age=23 ± 2 yrs.; mass=68.3 ± 9.6 kg; height=1.70 ± 0.08 m) completed 4000 steps on an instrumented treadmill on three separate days. Each day corresponded to a different ambulation speed: slow (preferred walking speed), medium (+50% of slow), and fast (+100% of slow). Synchronized ground reaction force and video data were collected to evaluate walking mechanics. Blood samples were collected pre-, post-, 30-minute post-, and 60-minute post-ambulation to determine serum COMP concentration at these times. Serum COMP increased 29%, 18%, and 5% immediately post ambulation for the fast, medium, and slow sessions (p<0.01). When the speeds were pooled, peak ankle inversion, knee extension, knee abduction, hip flexion, hip extension, and hip abduction moment, and knee flexion angle at impact explained 61.4% of total variance in COMP concentration change (p<0.001). These results indicate that (1) certain joint mechanics are associated with acute change in serum COMP due to ambulation, and (2) increased ambulation speed increases serum COMP concentration.