Patellar Tendon Loading During Dynamic Landings: How this is Moderated by Fatigue and the Presence of a Patellar Tendon Abnormality

BACKGROUND Patellar tendinopathy is a complex overuse knee injury common in sportsinvolving repetitive jumping and landing, in which repetitive loading is the mostfrequently reported causative factor associated with patellar tendinopathy. In order toprovide evidence for the development of prevention and rehabilitation programs forpatellar tendinopathy, research is required to broaden our understanding of the riskfactors associated with patellar tendinopathy. THESIS AIM The primary purpose of this thesis was to systematically investigate andcharacterise the patellar tendon loading generated during dynamic landings, and theinfluence of fatigue and the presence of a patellar tendon abnormality on diagnosticimaging (PTA) on these loads. METHODS To achieve the thesis aim, the thesis was completed in three parts. Part I (Chapter 2) assessed whether lower limb symmetry during a stop-jump landing task in16 male athletes with normal patellar tendons could be assumed. Then the validity andreliability of an experimental protocol designed to induce lower limb fatigue wasassessed (Chapter 3), in which 13 healthy male athletes performed the fatigue protocolon three separate occasions. The participants performed sets of 30 submaximal stretchshorteningcycle efforts immediately followed by 30 seconds rest during which theparticipants‟ kinetics and kinematics were quantified and blood lactate samplesrecorded. The experimental protocol that was developed in Part I (Chapter 2), was thenused to investigate the landing technique and patellar tendon loads generated during thelanding phases of a stop-jump task by 16 male athletes with healthy patellar tendons (Chapter 4), and between seven male athletes with a PTA but with no previous historyor clinical signs of patellar tendon injury who were then matched to seven male athleteswith normal patellar tendons (Chapter 6). Part II and III used the experimental protocolthat was developed in Part I (Chapter 3) to investigate the effect of fatigue on landingtechnique and patellar tendon loads generated during a stop-jump movement by 16 maleathletes with normal patellar tendons (Chapter 5) and by seven asymptomatic athleteswith a PTA (Chapter 7). During each stop-jump trial (Chapters 2, 4-7), the participants‟ground reaction forces (GRF) were recorded, three-dimensional kinematics estimated,and FPT calculated by dividing the net knee joint moment by the patellar tendon momentarm. MAJOR CONCLUSIONS In characterising the patellar tendon loads generated during the landing phasesof a stop-jump task, it was evident that athletes with normal patellar tendons were ableto reduce their patellar tendon loads when fatigued. This was achieved by altering theirlanding technique in a way which may have a protective effect and potentially decreasethe likelihood of patellar tendon pathologies in vulnerable athletes. In contrast,asymptomatic athletes with a PTA utilised a different lower limb landing technique thantheir healthy counterparts with normal patellar tendons, by landing with greater kneeflexion and utilising a hip extension rather than a hip flexion strategy. Theseasymptomatic athletes with a PTA, however, were unable to modify either their patellar tendon load or their landing technique in response to fatigue. It was speculated thatthese asymptomatic athletes with a PTA, may be less able to adapt to changes evokedby fatigue and are therefore at risk of developing patellar tendinopathy due to higherpatellar tendon loading