Subjective and Objective Assessment of Physically Active People with Knee Injury

Knee injuries are highly prevalent in physically active individuals and are frequently associated with sport participation. Independently of the nature of the injury, subjective and objective clinical measures are used to assess, monitor and evaluate treatment outcomes in this population. To be clinically meaningful, these outcome measures should be relevant to the condition, the anatomical area, the individual or population, and importantly, possess adequate psychometric properties. Despite a high prevalence of knee injuries, there are several aspects of the subjective and objective knee evaluation in physically active individuals that remain unclear or have not been considered in previous research.The main aim of the present thesis was to fill some of the gaps identified in the literature regarding both subjective and objective knee measures in physically active individuals. Therefore, this thesis was divided into two distinct parts. The first part looked at the patient-reported outcome (PRO) measures of the knee and physical activity, and consisted of two studies. The first study was a systematic review conducted to explore the PRO measures that are commonly used in the evaluation of physical activity and return to sport following autologous chondrocyte implantation (ACI). Aiming as well, to provide a critical analysis of these instruments from a rehabilitative perspective. This review revealed not only the heterogeneity in the selection, but also in the timing and reporting of patient-reported activity scoring instruments following ACI, which makes a systematic comparison difficult and introduces bias into the interpretation of these outcomes. Another important finding of this review, was that the instruments currently used to evaluate postoperative outcomes in an articular cartilage repair population do not always fulfil the rehabilitative needs of physically active individuals. The second study was conducted in recreational marathon runners and aimed to provide normative values for a widely used knee specific PRO measure in athletes with knee injury, the Knee Injury Osteoarthritis Outcome Score (KOOS). Alongside the normative KOOS subscales values stratified by age group and history of knee injury that were presented, this study also showed that recent history of knee running-related injury (RRI) has a negative impact on the KOOS scores. In runners with no history of knee RRI, the results observed suggested a lack of interaction between KOOS subscale values and age. Furthermore, the KOOS values seen were substantially higher compared to previously published normative population-based KOOS values.

The second part of the present thesis comprised three experimental studies concerning single-leg cycling (SLC) exercise testing, in particular assessing the potential use of the self-paced test (SPT) concept as an objective measure following knee surgery. The first study analysed the reliability of a 5x2 min stages SPT anchored to the rate of perceived exertion (RPE) for SLC exercise testing. This study showed that this test protocol elicits reliable cardiorespiratory and metabolic responses. The second study examined the validity of the SPT protocol used in the previous study, through a concurrent comparison against a conventional fixed power incremental SLC exercise test. This investigation showed that the 5x2 min SPT provides a valid objective means for assessing peak aerobic capacity in SLC exercise testing. Moreover, it may be associated with increased activity enjoyment comparatively to conventional testing. The third and last experimental study investigated the effect of a 10 kg counterweight device (CW10) on cardiorespiratory, metabolic and perceptual responses to SLC exercise testing. The results of this study demonstrated that the CW10 despite eliciting an improvement in the activity enjoyment, did not affect peak cardiorespiratory and metabolic responses to SLC exercise testing. When matched for test duration the SPT elicited higher peak power output and peak oxygen consumption than conventional incremental testing, regardless of the CW10 usage or not. In conclusion, the original work of the present thesis increases the body of knowledge of two distinct, but complementary fields in the subjective and objective knee assessment of physically active individuals. The outcomes provided both on PRO measures and SLC exercise testing, may have impact on the clinical practice of clinicians, sport rehabilitation professionals and researchers.