Arthritis is a general medical term used to describe a disorder in which the smooth cartilagenous layer that lines a joint is lost, resulting in bone grinding on bone during joint movement. Symptoms generally include joint pain and stiffness. Other symptoms may include redness, warmth, swelling, and decreased range of motion of the affected joints. In certain types of arthritis, other organs, such as the skin, are also affected. Onset can be gradual or sudden.

There are several types of arthritis. The most common forms are osteoarthritis (most commonly seen in weight-bearing joints) and rheumatoid arthritis. Osteoarthritis usually occurs as a person ages and often affects the hips, knees, shoulders, and fingers. Rheumatoid arthritis is an autoimmune disorder that often affects the hands and feet. Other types of arthritis include gout, lupus, spondyloarthritis, and septic arthritis. These are inflammatory based types of rheumatic disease.

Early treatment for arthritis commonly includes resting the affected joint and conservative measures such as heating or icing. Weight loss and exercise may also be useful to reduce the force across a weight-bearing joint. Medication intervention for symptoms depends on the form of arthritis. These may include anti-inflammatory medications such as ibuprofen and paracetamol (acetaminophen). With severe cases of arthritis, joint replacement surgery may be necessary.

Osteoarthritis is the most common form of arthritis affecting more than 3.8% of people, while rheumatoid arthritis is the second most common affecting about 0.24% of people. In Australia about 15% of people are affected by arthritis, while in the United States more than 20% have a type of arthritis. Overall arthritis becomes more common with age. Arthritis is a common reason people are unable to carry out their work and can result in decreased ability to complete activities of daily living. The term arthritis is derived from arthr- (meaning 'joint') and -itis (meaning 'inflammation').

Classification There are several diseases where joint pain is the most prominent symptom. Generally when a person has "arthritis" it means that they have one of the following diseases: Hemarthrosis Osteoarthritis Rheumatoid arthritis Gout and pseudogout Septic arthritis Ankylosing spondylitis Juvenile idiopathic arthritis Still's disease Psoriatic arthritis

Joint pain can also be a symptom of other diseases. In this case, the person may not have arthritis and instead have one of the following diseases: Psoriasis Reactive arthritis Ehlers–Danlos syndrome Iron overload Hepatitis Lyme disease Sjögren's disease Hashimoto's thyroiditis Celiac disease Non-celiac gluten sensitivity Inflammatory bowel disease (including Crohn's disease and ulcerative colitis) Henoch–Schönlein purpura Hyperimmunoglobulinemia D with recurrent fever Sarcoidosis Whipple's disease TNF receptor associated periodic syndromesubscription needed Granulomatosis with polyangiitis (and many other vasculitis syndromes) Familial Mediterranean fever Systemic lupus erythematosus

An undifferentiated arthritis is an arthritis that does not fit into well-known clinical disease categories, possibly being an early stage of a definite rheumatic disease.

Signs and symptoms Extra-articular features of joint disease Cutaneous nodules Cutaneous vasculitis lesions Lymphadenopathy Oedema Ocular inflammation Urethritis Tenosynovitis (tendon sheath effusions) Bursitis (swollen bursa) Diarrhea Orogenital ulceration Pain in varying severity is a common symptom in most types of arthritis. Other symptoms include swelling, joint stiffness, redness, and aching around the joint(s). Arthritic disorders like lupus and rheumatoid arthritis can affect other organs in the body, leading to a variety of symptoms including: Inability to use the hand or walk Stiffness in one or more joints Rash or itch Malaise and fatigue Weight loss Poor sleep Muscle aches and pains Tenderness Difficulty moving the joint

Causes Several factors contribute to the development of arthritis, differing on the type of arthritis.

Osteoarthritis occurs from damage to joint cartilage from prior injury or long-term wear-and-tear, resulting in bone-to-bone contact and grinding. The resulting arthritis can occur over years, or be worsened by further injury or infection. If joint cartilage is severely damaged, inflammation and swelling may add to the extent and pain of osteoarthritis.

In rheumatoid arthritis, the immune system itself, which normally serves to protect against infection and diseases, attacks the lining of the joint capsule, causing inflammation and swelling.

Gout is a form of arthritis caused by excessive uric acid production, resulting in urate crystals depositing in joints, particularly in extremities, such as toes. Urate levels in the blood may increase from consuming purine-rich foods or from body factors affecting urate clearance from the blood, a topic remaining under study.

Arthritis types may also include ankylosing spondylitis, juvenile idiopathic arthritis, psoriatic arthritis, and reactive arthritis, among others.

Risk factors There are common risk factors that increase a person's chance of developing arthritis later in adulthood. Some of these are modifiable while others are not.

Some common risk factors that can increase the chances of developing osteoarthritis include obesity, prior injury to the joint, type of joint, and muscle strength.

The risk factors with the strongest association for developing inflammatory arthritis (such as rheumatoid arthritis and lupus arthritis) are the female sex, a family history, age, obesity, joint damage from a previous injury, and exposure to tobacco smoke.

Smoking has been linked to an increased susceptibility of developing arthritis, particularly rheumatoid arthritis.

Diagnosis

Diagnosis is made by clinical examination from an appropriate health professional, and may be supported by tests such as radiologic imaging and blood tests, depending on the type of suspected arthritis. Pain patterns may vary depending on the type of arthritis and the location. Rheumatoid arthritis is generally worse in the morning and associated with stiffness lasting over 30 minutes. On the other hand, with osteoarthritis, the pain tends to initially be related to activity and then becomes more constant over time.

Important features to look out for include the following:

Rate of onset of symptoms Pattern of joint involvement Symmetry of symptoms Early morning stiffness Associated tenderness around the joint Locking of joint with inactivity Aggravating and relieving factors, and/or Presence of systemic symptoms

Physical examination may include observing the affected joints, evaluating gait, and examining the skin for findings that could be related to rheumatological disease or pulmonary inflammation. Physical examination may confirm the diagnosis or may indicate systemic disease. Chest radiographs are often used to follow progression or help assess severity.

Screening blood tests for suspected arthritis include: rheumatoid factor, antinuclear factor (ANF), extractable nuclear antigen, and specific antibodies.

Rheumatoid arthritis patients often have elevated erythrocyte sedimentation rate (ESR, also known as sed rate) or C-reactive protein (CRP) levels, which indicates the presence of an inflammatory process in the body. Anti-cyclic citrullinated peptide (anti-CCP) antibodies and rheumatoid factor (RF) are two more common blood tests when assessing for rheumatoid arthritis.

Imaging tests like X-rays are commonly utilized to diagnose and monitor arthritis. Other imaging tests for rheumatoid arthritis that may be considered include computed tomography (CT) scanning, positron emission tomography (PET) scanning, bone scanning, and dual-energy X-ray absorptiometry (DEXA).

Osteoarthritis

Osteoarthritis (OA) is the most common form of arthritis. It affects humans and other animals like dogs, cats, and horses. It can affect both the larger joints (i.e. knee, hip, shoulder, etc.) and the smaller joints (i.e. fingers, toes, foot, etc.) of the body. Caused by daily wear and tear of the joint, this can speed up its progression. OA results from cartilage breakdown, leading to bones rubbing directly and eroding each other. The symptoms typically begin with minor pain during physical activity, but can eventually progress to be present at rest. The pain can be debilitating and prevent one from doing activities that they would normally do as part of their daily routine. OA typically affects the weight-bearing joints, such as the back, knee and hip due to the mechanical nature of this disease process. Unlike rheumatoid arthritis, OA is more common in the elderly, with increased age being the strongest predictor, likely due to declining chondrocytes ability to maintain cartilage. Over 30 percent of women have some degree of OA by age 65. The primary diagnostic tool for OA is X-ray imaging of the joint. Findings on X-ray that are consistent with OA include joint space narrowing (due to cartilage breakdown), bone spurs, sclerosis, and bone cysts.

Rheumatoid arthritis

Rheumatoid arthritis (RA) is a disorder in which the body's own immune system starts to attack body tissues specifically the cartilage at the end of bones known as articular cartilage. The attack is not only directed at the joint but to many other parts of the body. RA often affects joints in the fingers, wrists, knees and elbows, is symmetrical (appears on both sides of the body), and can lead to severe progressive deformity in a matter of years if not adequately treated. RA usually onsets earlier in life than OA and commonly affects people aged 20 and above. In children, the disorder can present with a skin rash, fever, pain, disability, and limitations in daily activities. With earlier diagnosis and appropriate aggressive treatment, many individuals can obtain control of their symptoms leading to a better quality of life compared to those without treatment.

One of the main triggers of bone erosion in the joints in rheumatoid arthritis is inflammation of the synovium (lining of the joint capsule), caused in part by the production of pro-inflammatory cytokines and receptor activator of nuclear factor kappa B ligand (RANKL), a cell surface protein present in Th17 cells and osteoblasts. Osteoclast activity can be directly induced by osteoblasts through the RANK/RANKL mechanism.

Lupus

Lupus is an autoimmune collagen vascular disorder that can be present with severe arthritis. In fact, about 90% of patients with Lupus have musculoskeletal involvement. Symptoms in these patients can often mimic those of rheumatoid arthritis with similar stiffness and pain patterns. Joints in the fingers, wrist, and knee tend to be the most affected. Other features commonly seen in patients with Lupus include a skin rash (pictured on the right), extreme photosensitivity, hair loss, kidney problems, and shortness of breath secondary to scarring that occurs in the lungs.

Gout

In the early stages of gout, usually only one joint is affected; however over time, many joints can become affected. Gout most commonly occurs in joints located in the big toe, knee, and/or fingers. During a gout flare, the affected joints often become swollen with associated warmth and redness. The resulting pain can be significant and potentially debilitating. When one of these flares occurs, management involves the use of anti-inflammatories, such as NSAIDs, colchicine, or glucocorticoids. In between gout flares, it is recommended that patients take medications that decrease the production of uric acid (i.e. allopurinol, febuxostat) or increase the elimination of uric acid from the body (i.e. probenecid).