Knee osteoarthritis is a degenerative disease of the knee that results in the wearing away of the cartilage between the bones of the joint. This reduces the cushioning effect of cartilage, which can lead to decreased movement, stiffness and pain. As we get older cartilage takes a longer time to heal so it is not surprising that the most common cause of knee osteoarthritis (OA) is age. 

According to the World Health Organization (WHO), “Up to 40% of people over 70 suffer with osteoarthritis of the knee.”1 Although there is a higher prevalence of knee OA in middle-aged and elderly individuals it is not exclusive to these groups. Knee OA can occur in young adults, most commonly as a result of injury to the knee, which leads to deconditioning of the musculoskeletal system. Obesity is also a risk factor for OA due to an increased load placed on the
knee joint.2

As knee OA is a degenerative disease patients gradually experience an increase in stiffness, swelling, and pain in their joint. This makes daily activities like walking up a flight of stairs quite difficult and in severe cases of OA mobility of the knee is compromised. OA can be diagnosed through examination and x-ray and magnetic resonance imaging (MRI) scans. Management of the disease varies from individual to individual and would depend on a variety of factors including age, severity of the disease, lifestyle and the patient’s treatment preference.

 WHO predicts that knee OA is likely to become a leading cause of disability among men and women globally.3 This would put a significant strain on healthcare systems across the world and would have economic repercussions, so it is understandable that treatments are constantly evolving so that patients can be treated more successfully and cost-effectivly.

How is knee osteoarthritis treated? 

The main goal when treating knee OA is to relieve pain and improve the mobility of patients. This is done through a combination of therapies and treatments. Weight loss as well as exercise (strengthening of the muscles around the knee) have been shown to significantly reduce pain in patients and increase their mobility. This is particularly true for older over-weight patients with knee OA and the combination of the two therapies is more effective than either intervention alone.4 Patients are often prescribed painkillers, non steroidal anti-inflammatory drugs (NSAIDs) and various braces to cope with the condition. In patients with severe pain and/or a diminished quality of living opiates can be used but these patients must be monitored carefully.5 Hyaluronic acid, which is an important component of cartilage can be injected directly into the knee—intra-articular hyaluronic acid (IAHA). The efficacy of IAHA has been investigated in many studies and one such study determined that it had a small effect when compared with an intra-articular placebo. The highest molecular weight hyaluronic acid has shown to be more effective than the lower molecular weight hyaluronic acid in treating knee OA.6

Generally these studies have not reached a consensus when it comes to the effectiveness and safety of the hyaluronic acid. A review comparing the efficacy of IAHA to NSAIDs in the treatment of knee OA found that there was not much of a significant difference between the two. IAHA however had a favourable safety profile and would therefore be a viable alternative to NSAIDs especially for the elderly who are at higher risk for adverse events.7 Detractors of the use of IAHA in treatment claim that it is clinically ineffective and may in fact be associated with a greater risk of adverse events.8

Knee replacement surgery
When knee OA is very severe or other treatments have not worked, surgery is often considered. Knee replacement surgery (total knee arthroplasty) is one of the most common treatments for osteoarthritis. In the UK more than 70,000 knee replacements are carried out each year with the majority of patients being over the age of 65 years. Knee surgery has changed radically over the last two centuries. In the past severe diseases of the knee were treated by arthrodesis, which involved joint ossification but this resulted in a high degree of knee stiffness. This warranted a new form of knee treatment and it was only until the early third of the 20th century that soft tissue arthroplasty became a dominant thought in the surgical communities. 

Brief history of knee arthroplasty
In the 1960s Freeman and Swanson in London and Insall and Walker in New York, USA contributed to the development of the condylar knee replacement through the use of a cobalt-chrome femoral prosthesis articulating with a high density polyethylene tibial tray. This permitted rotation of the knee as well as 90 degree of flexion. The Freeman-Swanson ICLH knee prosthesis was the first to be subject to a multi-centre trial. In the 80s, Freeman and Samuelson modified the ICLH prosthesis by displacing the tibial articular surface posteriorly and decreasing the size of the posterior tibial lip to allow a greater deal of flexion.

Success of knee arthroplasty operations is measured by postoperative knee flexion. A healthy human knee is capable of 150 degrees of flexion whereas a prosthetic knee achieves just over 110 degrees of flexion. Whilst 105 degrees to 110 degrees of flexion is adequate for carrying out daily activities, individuals are still limited in their motion: for example squatting or sitting may be difficult. It has been shown that high flex designs allow more knee flexion in patients post operatively but the question of whether this extra degree of flexion is needed for the average patient has been widely debated. Several studies agree that although high flex designs allow more knee mobility, patients without any special lifestyle demands will rarely utilise the increase flexion in their everyday activities.10,11

Surgical techniques for knee arthroplasty are constantly evolving in order to increase effectiveness of the implant and reduce the post-operative recovering period.
Minimally invasive surgery (MIS) aims at reducing soft tissue damage, postoperative pain and the size of the incision. There is however a concern that because of the limited exposure the implant may not be positioned correctly and this could increase complication rates.12

Total knee arthroplasty, however, is not the only surgical treatment for patients with severe knee osteoarthritis—partial knee replacements can be performed on patients as an alternative treatment to total knee arthroplasty. Patients who qualify for partial knee replacements usually have one sided knee damage.

Partial knee replacement is a much smaller operation than total knee arthroplasty and involves less bone being removed. This results in a shorter recovery period and can lead to more mobility in the knee post-operatively.13

Peri-operative care
The main goals of peri-operative care programmes for patients undergoing knee replacement surgery are to minimise complications, reduce morbidity and ensure a quick recovery period. If these goals are achieved patients spend less time in the hospital post-operatively and the rates of readmission will decrease. 

One of the most important aspects of peri-operative care is patient education. Patients should be informed of what to expect during and after surgery. Patients who are educated pre-operatively on rehabilitation after surgery are better equipped to face these stresses and are likely to have a reduced hospital stay and also reduced pain-medication usage.14

Total knee arthroplasty, like any surgical procedure, is associated with a degree of pain post-operatively. Studies suggest that a combination of pre-operative and post operative anti-inflammatory medications, intra-articular anaesthetic and regional anaesthetic can effectively be used for pain control post operatively.15 Nutrition is also important in peri-operative care as it is likely that patients with low serum albumin and transferrin levels pre-operatively will have delayed wound healing, increased morbidity and a longer than normal hospital stay. 

What about other forms of arthritis?
We have discussed osteoarthritis in quite some detail but there are other (less common) forms of arthritis that can have deleterious effects. Rheumatoid arthritis (RA) is an autoimmune disorder whereby the body’s defence systems attack tissues and joints causing inflammation, typically of the small joints in hands and feet. This type of arthritis can affect the organs of the body—such as the heart, lungs, skin, kidneys and eyes. Gout is another form of arthritis, which is characterised by a sudden burning pain and swelling in a joint—usually the big toe. Gout occurs when uric acid in the blood is so high in concentration that it forms crystals in the joints. Gout attacks can be recurrent unless treated.

Conclusion
Arthritis affects millions of people around the world and it has the potential to be severely debilitating; when people have reduced mobility and are in pain their quality of life changes drastically. This can have physical, emotional and financial consequences on individuals especially among the elderly who are also more prone to other health problems. Treatment for arthritis however has greatly improved over the last few decades and with technological advances in medicine future treatment options look promising.

Conflict of interest: none declared.
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