Tribology is the science of interacting surfaces in relative motion. It is specifically concerned with the friction, wear and lubrication of these surfaces. Although tribology has conventionally been associated with the surface interaction of mechanical systems, concepts of tribology have also been important in the study of biological systems. Biotribology is one of the newest fields to emerge in the discipline of tribology. It can be described as the study of friction, wear and lubrication of biological systems, mainly synovial joints such as the human hip and knee. Osteoarthritis (OA) is partially characterized by the loss of articular cartilage from the contacting surface of the articulating bones in synovial joints. Although it has been studied extensively, the exact pathways and pathogenesis of OA have yet to be determined. Several factors have been cited as possible contributors to the condition. These factors can primarily be grouped into two categories of mechanical or biochemical abnormalities. Research in biotribology enables the examination of both the mechanical and biochemical factors involved in joint lubrication and OA. This research has focussed on the mechanisms of normal joint lubrication, as well as the possible connections between biotribology and osteoarthritis. Particular emphasis is placed on the effects of biochemical changes and environment on cartilage wear and damage. Studies were carried out using a test device developed to study the tribological properties of articular cartilage, in vitro. A cartilage-on-cartilage test configuration was used with bovine articular cartilage and a cartilage-on-stainless steel configuration used with lapine articular cartilage. Articulating surfaces were put in sliding contact under a normal load. Natural and biochemically modified environments were created to simulate possible normal and pathologic in vivo conditions. Wear and friction of the articular cartilage were measured and related to biochemical environments which are suspected in clinical cases of OA. Quantitative measurement of cartilage wear was achieved through hydroxyproline assay of the post-test lubricants. Surface and subsurface damage were also examined through the use of scanning electron microscopy and histological staining techniques. The results of four separate studies demonstrated that: (1) exposure of bovine cartilage to collagenase-3, an enzyme suspected in the cartilage degeneration seen in OA, significantly increased cartilage wear (p = 0.001); (2) lapine cartilage with surgically induced OA exhibited higher coefficients of friction, but no significant increase in wear over normal cartilage from the same animal; (3) the addition of white blood cell lysate, comparable to what would be seen in mild joint inflammation, to synovial fluid significantly increased cartilage wear over normal synovial fluid (p = 0.002); (4) the removal of "boundary lubricating" surface-active phospholipids (SAPLs) from normal synovial fluid had no significant effect on cartilage wear. These results demonstrate that biochemical changes in the cartilage, as well as the synovial fluid, can lead to increased wear of and damage to the articular cartilage surface. How these changes may occur in living systems remains to be determined. The use of the tribological test device developed and various analytical techniques has made it possible to quantitatively evaluate the effects of biochemical changes and environment on the wear and damage of articular cartilage. These studies have demonstrated that research in biotribology has the potential to make significant contributions to the current knowledge not only of normal joint lubrication but of joint pathology as well. / Ph. D.

In our aging population, arthritis is becoming an increasingly common problem. Pain, loss of joint function and other negative affects make arthritis a major health problem. The most common form of arthritis, osteoarthritis, is caused by the "wear and tear" of articular cartilage on the surface of bones in synovial joints. It is a chronic problem that is slowed with different types of therapies, including pharmaceutical, nutritional and surgical, but to date the wearing down of the cartilage cannot be stopped or reversed. Normal, mature, articular cartilage does not spontaneously repair itself after an injury. In light of this, several surgical techniques are being developed to repair degenerate and/or osteoarthritic cartilage. One such approach uses Autologous Chondrocyte Implantation (ACI). Dr. Mats Brittberg, and associates at Goteborg University in Sweden began using this cartilage repair procedure in 1987. Other techniques attempt to stimulate the subchondral bone to generate cartilage, such as Abrasion Arthroplasty. Still others use tissue grafts to attempt to repair lesions in cartilage. The surface biomechanics of these repaired tissues have not yet been studied. How well does the repaired cartilage resist wear? How long will it last? How does the repaired cartilage compare to "normal" cartilage in terms of wear-resistance? It is the goal of this research to gain initial knowledge to help answer these questions. Dr. Brittberg has provided 17 sample of cartilage, from 9 Swedish patients, including repaired and normal pairs using the aforementioned repair techniques and others, as well as a degenerate and normal cartilage pair. The intention of this paper is to report the findings of experiments performed using these samples, and compare the wear-resistance of repaired and degenerate cartilage to that of normal cartilage. Wear and friction tests were carried out on 2 mm diameter specimens using a biotribology device and a new, modified technique developed specifically for these small samples. The cartilage samples were mounted, using specially designed adapters, in our biotribology device for oscillating contact against polished stainless steel disks at a constant applied normal load, oscillating frequency, and test time. A buffered saline solution was used as the lubricant. Cartilage wear was determined from hydroxyproline analysis of the test fluid and washings from the wear test. Thin layers of transferred cartilage-like films to the stainless steel disks were also analyzed. Also, friction data was recorded throughout the tests. The results of these experiments show that: 1) For the two pairs of ACI repaired cartilage, the repaired cartilage gave substantially less wear than that of normal cartilage. 2) For all other repair techniques tested, the repaired cartilage produced more wear than normal cartilage. 3) The single osteoarthritic cartilage tested produced similar wear to that of normal cartilage. This is surprising since the current thought is osteoarthritic cartilage is more susceptible to wear. 4) The hydroxyproline concentration, by weight, of cartilage increases after the wear test. 5) Friction levels were in the boundary lubrication regime, and had no correlation with the amount of wear. To our knowledge, this research represents the first controlled "in vitro" study of an important unknown in cartilage repair, i.e., the wear-resistance of the repaired cartilage. It shows that ACI produces a cartilage with very good wear-resistance, better than that of other repair techniques, and possibly better than normal, healthy cartilage. ACI and its applications to the treatment of degenerate and osteoarthritic joints are promising, and studies will continue to investigate this and other types of cartilage repair. / Master of Science

The ability to kneel is an important function of the knee joint, as it is required for many daily activities, including religious practices, professional occupations and recreational pursuits. The inability to kneel following total knee arthroplasty (TKA) is frequently a source of disappointment. This work investigates patients' understanding of the term 'kneeling' and what proportion of patients can kneel before and after TKA, as well as identifying the factors that can affect the ability to kneel following TKA. The underlying hypothesis tested was: 'There are no differences between kneeling ability before and after TKA'. Kneeling ability after TKA may be affected by many factors, including patient-specific factors, the extent of wear on RPC (Retro patellar Cartilage), postoperative AKP (Anterior Knee Pain) and post-operative ROM (Range of Motion). Thus a consecutive series of TKA patients were assessed to test the afore-mentioned hypothesis. In particular, the thesis has examined: • Interpretation of kneeling and perceptions of kneeling ability after TKA. • The extent of wear on Retro Patellar Cartilage (RPC) and its correlation to kneeling ability. • Sensory changes in the knee after TKA. • Preoperative and Postoperative Anterior Knee Pain (AKP) assessment. • The reality of kneeling ability before and after TKA. • Postoperative ROM of the knee and its correlation to kneeling function. The advice offered by healthcare professionals may contribute to a low postoperative rate of kneeling. The patellofemoral joint plays an essential role in knee function and a person's kneeling ability, may be greatly affected by the performance of this joint. Firstly, this study analysed the responses of two samples of participants drawn from diverse cultural backgrounds (Christian and Muslim), it examined their primary interpretation of what kneeling constitutes, along with a subjective assessment of the importance of kneeling in their everyday lives. Secondly, it explored patients' perceptions of their kneeling ability after TKA, with a comparative analysis of their responses to the kneeling questionnaire specifically constructed by the author and also the question in relation to kneeling in the Oxford Knee Score (OKS). The third component investigated retro-patellar cartilage (RPC) morphology using intraoperative examination and standardised photography. Fourthly, a cohort of patients listed for TKAs was followed prospectively, in order to assess their kneeling ability prior to and following treatment, along with identifying the factors that could affect this function, i.e. knee pain, range of motion, sensory changes and sensitivity to pain on the anterior aspect of the knee as assessed with dolorimetry. Differences were detected in the subjective interpretation of the kneeling function, as well as its importance, for the two diverse cultures involved in this study. Pain, as opposed to poor range of movement, was identified as the main reason which led to kneeling difficulties. The majority of respondents reported that it was either extremely difficult or impossible to kneel on the operated knee. The high flexed position (required for prayer in certain cultures) was the most difficult position to achieve for most of the patients. Prior to surgery, 30 patients were seen during this period, 15 (50%) out of 30 consecutive patients were unable to kneel in any position whatsoever. Of those who could kneel to some degree, the most common posture that they could achieve was the upright kneeling position. Considerable variations were found to occur in patients' understanding of the term 'kneeling'. Consequently, this has significant implications for the design and interpretation of questions in relation to kneeling for diverse cultures, which are characterised by distinct lifestyles. The current patient-based selfV administered questionnaires, such as the OKS, although useful as a simple measure of overall knee function, were found to have limitations as an effective assessment tool in the measurement of kneeling function either before or after TKA and indicate that there is a need for a culturally appropriate questionnaire to assess kneeling function. Retro-patellar cartilage lesions were very prevalent in patients undergoing TKA. However, no significant correlation existed between the total amount of retro-patellar cartilage wear and the ability to kneel. Patients were more likely to be able to kneel if the cartilage of the superior facets of the patella were disease free (P=0.02). At the six months post-surgery stage, of the 14 consecutive patients, who could kneel pre-operatively 6 were able to kneel post-operatively. Of the 13 consecutive patients who were unable to kneel pre-operatively, all were unable to kneel post-operatively. Knee pain was the main reason attributed to this difficulty. However, no link was found to occur between sensory changes and kneeling function in the patients who participated in the study, after TKA performed via an anterior midline incision.