Osteoarthritis overview

Explained – what is it and what causes it?

Osteoarthritis is the most common type of arthritis.[1] Arthritis is the inflammation of one or more joints of the body so that they are painful and swollen, with redness and warmth of the overlying skin and a reduced range of motion.

Osteoarthritis affects a type of joint called the synovial joints and is characterised by:[1-3]

  • Cartilage loss, mainly at the maximum load-bearing part of the joint
  • New bone formation at the margins of the joints (osteophytes)
  • Changes in subchondral bone
  • Recurrent synovitis, inflammation of the membrane that lines the capsule of the joint (synovium).

These changes in the cartilage and bone (thinning of the cartilage, and remodelling of the bone) slowly change the shape of joints affected by osteoarthritis.[1] 

The condition may have a known precipitating factor, for example, rupture of a ligament. However, the causative factor is not always clear.[1] 

Symptoms and signs

The main symptoms of osteoarthritis include:[1]

  • Pain
  • Restriction in function; for example, a reduced range of motion.

Pain from osteoarthritis usually affects just one or a few joints and appears slowly over a period of months. Typically, the pain is more severe on some days than others. It is mainly replique montre related to movement and putting weight on the joint.[1] 

In the past, it was generally believed that there was only a weak link between the features of knee osteoarthritis on X-ray and knee pain, particularly in the early stages. However, more recent research shows that there is a notable association, even for mild stages of osteoarthritis of the knee.[4] 

If you place your hand over the joint affected by osteoarthritis, you may note a ‘crackling feeling’ (crepitus) on moving the joint; this is because the surfaces of the joint are rougher than usual. You may also feel bony lumps around the margins of the joint – these are the osteophytes – and perhaps note some wasting of the muscles around that joint.[1]

Risk factors and prevention

Risk factors include:[3,5]

  • Older age
  • Other conditions: both related to the musculoskeletal system (for example, other joint diseases) and unrelated to the musculoskeletal system (for example, obesity)
  • History of manual labour, particularly involving bending and carrying
  • Cigarette smoking
  • Having a close relative with osteoarthritis
  • Female gender
  • Previous history of major knee or hip injury or surgery
  • Obesity.

Prevention efforts should be targeted to people who have one or more of these risk factors for knee and hip osteoarthritis:[5] 

The key risk factors which can be modified are obesity (for osteoarthritis affecting the knee and hip), knee injury, and jobs requiring bending or carrying (for knee osteoarthritis).[5] Obesity is the main preventable risk factor that has been identified.[6] 

Tests and diagnosis

The only really useful investigation that has been identified to date for osteoarthritis is a simple X-ray, which may show up one or more of the typical features of osteoarthritis and assess the extent of change in joint structure.[1] 

However, additional investigations may be needed in young people with unexplained osteoarthritis – that is, no known precipitating factor.[1]

Choosing treatments

Moderate exercise seems to improve the function of the affected joint(s) and reduce pain and disability. There is a lot of strong evidence for the benefit of exercise therapy in knee osteoarthritis, in particular.[7] However, some research suggests that exercise may improve function and pain to a lesser extent in hip osteoarthritis.[8] 

An attempt should be made to minimise any factors that would worsen the condition; examples include losing weight if you are overweight, wearing shock-absorbing footwear, and wearing built-up shoes to even out leg lengths.[1] 

A wide variety of medications are available in the management of osteoarthritis. These medications may be taken by mouth (oral), rubbed directly onto the overlying skin of the joint (topical) or injected directly into the joint (intra-articular). Such medications include:[9] 

  • Oral and topical non-steroidal anti-inflammatory drugs (NSAIDs)
  • Intra-articular corticosteroids or hyaluronate
  • Opioids.

Both NSAIDs and corticosteroids are useful for their anti-inflammatory effects. However, NSAIDs may be given with another agent to protect the lining of the stomach (one example is a proton pump inhibitor), as they can increase the risk of gastrointestinal bleeding; in addition, the number of intra-articular corticosteroid injections should be limited to avoid side-effects.[9,10]

Intraarticular hyaluronate, the injection of hyaluronic acid into joints affected by osteoarthritis, has beneficial effects that take longer to appear but last longer than those of corticosteroid injections.[11] 

If conservative and medical treatments are not sufficient, surgery may help. The choice of surgical procedure depends on the severity of osteoarthritis and the joints affected, and characteristics such as occupation and age. Options include:

  • Arthroscopy
  • Osteotomy
  • Arthroplasty. [12] 

Arthroscopy involves inserting a very small instrument into the joint under anaesthetic, to view the inside of the joint and remove any loose debris within it. However, this procedure has not been shown to affect disease progression.[12] 

Osteotomy is a procedure to remove a part of the bone so that the weight load is transferred from the damaged part of the joint to another part, and is usually considered in younger people.[12] 

Arthroplasty, or joint replacement, is reserved for people who have severe osteoarthritis. It may be total or partial.[12] 

Outlook and living with

The course of osteoarthritis may differ from person to person. Risk factors for worsening function include pain, stiffness, reduced muscle strength, a lack of joint position sense (proprioception) and being overweight.[13] 

Certain tools may help in day-to-day functioning, for example special footwear and a walking stick for people with painful hip or knee arthritis.[1] 

Finally, novel ways to cope with osteoarthritis are always being explored. One small study suggested that the practice of Tai Chi, a Chinese art involving meditative, physical movements, may reduce pain, improve function and lessen any symptoms of depression in people with osteoarthritis of the knee.[14]  


1. Boon NA, Colledge NR and Walker BR. Davidson’s Principles and Practice of Medicine Churchill Livingstone Elsevier. 2006; 20th edition.

2. Fuerst M, Bertrand J, Lammers L et al. Calcification of articular cartilage in human osteoarthritis. Arthritis & Rheumatism 2009; 60: 2694–703.

3. Moskowitz RW. The burden of osteoarthritis: clinical and quality-of-life issues. Am J Manag Care. 2009; 15: S223-9.

4. Neogi T, Felson D, Niu J et al. Association between radiographic features of knee osteoarthritis and pain: results from two cohort studies. BMJ 2009; 339: b2844.

5. Felson DT and Zhang Y. An update on the epidemiology of knee and hip osteoarthritis with a view to prevention. Arthritis & Rheumatism 1998; 41: 1343-55.

6. Powell A, Teichtahl AJ, Wluka AE et al. Obesity: a preventable risk factor for large joint osteoarthritis which may act through biomechanical factors. Br J Sports Med 2005; 39: 4–5.

7. NJ Bosomworth. Exercise and knee osteoarthritis: benefit or hazard? Canadian Family Physician 2009 55: 871-8.

8. Fransen M, McConnell S, Hernandez-Molina G et al. Exercise for osteoarthritis of the hip. Cochrane Database of Systematic Reviews 2009, Issue 3.

9. Altman RD. Practical considerations for the pharmacologic management of osteoarthritis. Am J Manag Care 2009; 15: S236-43.

10. Bellamy N, Campbell J, Robinson V et al. Intraarticular corticosteroid for treatment of osteoarthritis of the knee. Cochrane Database Syst Rev 2006, Issue 2.

11. Brzusek D and Petron D. Treating knee osteoarthritis with intra-articular hyaluronans. Current Medical Research and Opinion 2008; 24: 3307-22.

12. Lützner J, Kasten P, Günther KP. Surgical options for patients with osteoarthritis of the knee. Nat Rev Rheumatol 2009; 5: 309–16.

13. Dekker J, van Dijk GM and Veenhof C. Risk factors for functional decline in osteoarthritis of the hip or knee. Curr Opin Rheumatol 2009; 21: 520-4.

14. C Wang, CH Schmid, PL Hibberd. Tai Chi is effective in treating knee osteoarthritis: A randomized controlled trial. Arthritis & Rheumatism 2009; 61: 1545–53.