In vivo validation of patellofemoral kinematics during overground gait and stair ascent.
Samuel Pitcairn, Bryson Lesniak, William Anderst
PMID 29929162WHAT IT FOUND
Biplane radiography measured patellar motion during walking within 0.69 mm and 2.9 degrees in four people with implanted markers.
Stair ascent errors were up to 0.44 mm and 2.1 degrees. Errors rose when the other leg obstructed the view.
Key findings
01The model-based tracking error during walking was 0.69 mm or less in translation and 2.9 degrees or less in rotation; during stair ascent, it was 0.44 mm or less in translation and 2.1 degrees or less in rotation.
02The other leg obstructed the patella in 51% of walking image pairs and 21% of stair ascent image pairs. When the patella was at least partly obstructed, average tracking error rose from 0.41 mm and 1.97 degrees to 0.55 mm and 2.76 degrees.
03Patellofemoral joint space tracking error was 0.90 mm or less during walking and stair ascent.
STILL TO COME
How it was doneWhat they foundWhat it means for PTs
Read the rest of this summary
You get three full summaries a month, free, and we do not ask for a card. Search, the TL;DRs and your library stay unlimited either way.
What it does not show
Only four subjects were tested, and 19 trials were analysed, so the results may not cover all knee anatomy or movement patterns. Only walking and stair ascent were tested; running, pivoting, and other movements were not validated. Three walking trials were excluded for one participant with BMI 37.3 because the other leg obstructed the patella, and two walking trials from other participants were excluded because the anterior patella edge was washed out. Obstruction by the other leg was common and increased tracking error. The femur markers were placed in a nearly straight line in one subject, so the femur was tracked with the model-based method rather than bead tracking for all participants. The study did not test whether abnormal patellar tracking causes anterior knee pain or whether treatments change it.
Declared interests
The paper lists NIH extramural and non-U.S. government research support. The authors declared no financial or personal conflicts, and they reported that study sponsors had no influence on data collection, analysis, or interpretation.
The easy way to misread this
Do not conclude that this study shows a treatment improves patellar tracking or that abnormal patellar tracking causes anterior knee pain. It only tested how accurately an imaging method measures patellar motion in four people, and errors increased when the other leg blocked the view.