Arthritis is a disease of aging leading to pain, lack of joint movement, particularly in hips and knees, and poor quality of life. The Global Burden of Disease Study 2019 reported those living with osteoarthritis had more than doubled since 1990 and this trend will continue due to "the epidemic of obesity". Knee osteoarthritis accounted for 61% of cases. In the UK, around 33% of those over 45 have sought treatment for osteoarthritis. The number with knee osteoarthritis is \>5million and estimated to increase a further 30% by 2030\. Estimated UK direct healthcare costs for treating arthritis in 2017 were £10.2billion. There is a rapidly increasing demand for treatment of osteoarthritis in young (35-55 years old) high activity patients who are still within their working life, so costs to society include the loss of productivity (36 million lost working days in the UK per year), general and psychological health, as well as costs of direct treatment. It is widely accepted by orthopaedic scientific societies and surgeons that conservative treatment fails many of these patients but that current joint replacement technologies, although very successful in older patients, are not suitable or efficient. Therefore, a new approach is needed to tackle this problem and return these individuals to their chosen lifestyle. Current knee replacement implants are made of plastic, metal and ceramics and cannot, like our natural bodies, repair themselves. Eventually they wear out. The operation to replace them, revision knee surgery, is more difficult and more likely to have problems than the initial surgery. Therefore, a knee replacement that does not wear out is desirable. To make this possible, we will develop constructs that make tissues to be used to replace areas damaged by osteoarthritis. We have already made supporting structures that are strong enough to be implanted and support cells to grow. This project will further develop these materials to regenerate complex tissues. This will remove the need to use metal, plastic, or ceramic to mend the knee joint. This will have other benefits, such as giving better movement as it is the same as a normal knee and reducing the chances of serious infections after operations by reducing the risk of biofilm formation. It will preserve the current approach to knee surgery so also allowing patients to benefit from the advances that have been made in knee surgery over the last 30 years which have significantly improved functional outcomes.

Arthritis is a disease of aging and leads to pain, lack of movement in joints, particularly hips and knees, and poor quality of life. The Global Burden of Disease Study 2016 has hip and knee osteoarthritis ranked as the 12th highest contributor to global disability. With an aging population and increasing obesity the number of people in the UK with knee osteoarthritis is over 5 million and estimated to increase a further 30% by 2030\. There is a rapidly increasing demand for treatment of osteoarthritis in young (35-55 years old) high activity patients. These patients are still within their working life so costs to society include the loss of productivity, general and psychological health, as well as those of direct treatment. It is widely accepted that conservative treatment fails many of these patients but that current joint replacement technologies, although very successful in older patients, are not suitable or efficient. Therefore, a new approach is needed to tackle this problem and return these individuals to their chosen lifestyle. Current knee replacement implants are made of plastic, metal and sometimes ceramics and so cannot, like our natural bodies, repair themselves so they eventually wear out. The operation to replace them, revision knee surgery, is more difficult and more likely to have problems than the first one. Therefore, a knee replacement that did not wear out would be more desirable. To make this a possibility, we will develop the first stage in making tissue structures that can be used to make components that could then replace the parts of the knee damaged by osteoarthritis. This will be by making the correct supporting structures needed for these tissues as they need to be strong enough to be made into components that can be implanted. This will remove the need to use metal, plastic or ceramic to mend the knee joint. This will have other benefits, it should give better movement as it is the same as a normal knee, it should reduce the chances of serious infections after operations as there is no "foreign" material such as metal, plastic or ceramic within the body for bacteria to attach to. It will preserve the current approach to knee surgery so it will also allow patients to benefit from the advances that have been made in knee surgery over the last 20 years which have significantly improved functional outcomes for patients.