Risk factors associated with a clinical presentation of patellar tendinopathy are patellar tendon ultrasonographic abnormality (PTA) and excessive loading. It remains unknown whether characteristics of an athlete's landing technique contribute to this excessive patellar tendon loading. This study investigated whether asymptomatic athletes with and without PTA had different landing strategies and hypothesized that asymptomatic athletes with a PTA would create higher patellar tendon loading and a different lower-limb landing strategy compared with athletes with normal patellar tendons.
Seven athletes with no previous history or clinical signs of patellar tendon injury with a PTA were matched to athletes with normal patellar tendons (controls). Participants performed five successful trials of a stop-jump task, which involved a simultaneous two-foot horizontal and then vertical landing. During each trial, the participants' ground reaction forces and lower-limb electromyographic data were recorded, the three-dimensional kinematics measured, and the peak patellar tendon force calculated by dividing the net knee joint moment by the patellar tendon moment arm.
Significant between-group differences in landing technique were mostly observed during the horizontal landing phase. Participants with a PTA created similar patellar tendon loading to the controls, but with altered sequencing, by landing with significantly greater knee flexion and extending their hips while the controls flexed their hips as they landed, reflecting a different muscle recruitment order compared with the PTA group.
The crucial part in the development of PTA and, in turn, patellar tendinopathy may not be the magnitude of the patellar tendon load but rather the loading patterns. This research provides clinicians with important landing assessment criteria against which to identify athletes at risk of developing patellar tendinopathy.
1Biomechanics Research Laboratory, University of Wollongong, New South Wales, AUSTRALIA; 2PRP Diagnostic Imaging, Wollongong, New South Wales, AUSTRALIA; 3Department of Physical Therapies, Australian Institute of Sport, Canberra, Australian Capital Territory, AUSTRALIA; and 4School of Exercise and Nutrition Sciences, Deakin University, Burwood, Victoria, AUSTRALIA
Address for correspondence: Julie R. Steele, Dip Teach, B.P.E. (Hons), Ph.D., F.A.S.M.F., Biomechanics Research Laboratory, University of Wollongong, Northfields Ave., Wollongong NSW 2522, Australia; E-mail: email@example.com.
Submitted for publication November 2009.
Accepted for publication March 2010.