Causes and Biological Mechanisms
Osteoarthritis is primarily caused by the gradual deterioration of cartilage, the slippery tissue that covers the ends of bones where they form a joint. As cartilage wears away, bones may rub against each other, causing friction and pain. The condition is not simply due to wear and tear; it affects the entire joint, causing changes in the bone and deterioration of the connective tissues that hold the joint together and attach muscle to bone. It also causes inflammation of the joint lining.

Risk Factors
Several factors increase the risk of developing osteoarthritis. Age is a primary factor, as the risk increases significantly as people get older. Women are more likely to develop the condition than men, particularly after age 50. Obesity is a major risk factor because extra weight adds stress to weight-bearing joints like the hips and knees, and fat tissue produces proteins that can cause harmful inflammation in and around the joints. Other risk factors include:

• Joint injuries, such as those from sports or accidents, which can increase the risk of osteoarthritis even years after the injury has healed.
• Repeated stress on the joint caused by jobs or sports that involve repetitive stress on a joint.
• Genetics, as some people inherit a tendency to develop the condition.
• Bone deformities, such as being born with malformed joints or defective cartilage.
• Certain metabolic diseases, including diabetes and hemachromatosis.

Prevention Strategies
While osteoarthritis cannot always be prevented, certain lifestyle changes can reduce the risk or delay its onset. Maintaining a healthy weight is one of the most effective ways to prevent osteoarthritis in the knees and hips. Participating in regular exercise helps strengthen the muscles around the joints to increase stability. To prevent injury-related osteoarthritis, it is important to avoid joint overuse and protect joints during sports or physical labor. Controlling blood sugar levels can also help, as high glucose levels may speed up the formation of molecules that make cartilage stiffer and more sensitive to stress.

Signs and Symptoms
Symptoms of osteoarthritis often develop slowly and worsen over time. The most common sign is pain in the affected joints during or after movement. Joints may feel stiff, particularly upon awakening or after being inactive, but this stiffness usually resolves within 30 minutes. Other clinical signs include:

• Tenderness when applying light pressure to or near the joint.
• Loss of flexibility, making it difficult to move the joint through its full range of motion.
• A grating sensation, known as crepitus, usually accompanied by a popping or crackling sound when using the joint.
• Bone spurs, which feel like hard lumps and can form around the affected joint.
• Swelling caused by soft tissue inflammation around the joint.

Diagnostic Evaluation
Clinicians diagnose osteoarthritis through a combination of physical examinations, symptom history, and imaging tests. During the physical exam, the doctor checks the affected joint for tenderness, swelling, redness, and flexibility. Imaging plays a key role in confirmation:

• X-rays can reveal a narrowing of the space between bones in the joint, indicating cartilage loss, and can show bone spurs.
• Magnetic Resonance Imaging (MRI) uses radio waves and a strong magnetic field to produce detailed images of bone and soft tissues, including cartilage, helpful for complex cases.

Differential Diagnosis
It is important to distinguish osteoarthritis from other forms of joint disease. Lab tests analyzing blood or joint fluid can help confirm the diagnosis by ruling out other conditions. For example, blood tests can exclude rheumatoid arthritis, an autoimmune condition. Joint fluid analysis involves drawing fluid from the affected joint to examine it for infection or crystals, which would suggest gout rather than osteoarthritis.

Medications
Medications can help relieve pain and improve function, primarily addressing symptoms rather than the underlying disease process. Acetaminophen has historically been used for mild to moderate pain, though nonsteroidal anti-inflammatory drugs (NSAIDs) like ibuprofen and naproxen sodium are often more effective at relieving osteoarthritis pain. Duloxetine, typically an antidepressant, is also approved to treat chronic pain, including osteoarthritis. Topical NSAIDs in the form of gels or creams can be applied directly to the joint to reduce systemic side effects.

Therapies and Procedures
Physical therapy is a cornerstone of management, helping to strengthen the muscles around the joint, increase flexibility, and reduce pain. Occupational therapy helps patients discover ways to perform everyday tasks without putting extra stress on their already painful joints. If conservative treatments fail, procedures may be considered:

• Cortisone injections into the joint can relieve pain for several weeks or months, though frequent use may damage the joint over time.
• Lubrication injections (viscosupplementation) involving hyaluronic acid may offer pain relief by providing some cushioning in the knee.
• Realigning bones (osteotomy) may be helpful if osteoarthritis has damaged one side of a knee more than the other.
• Joint replacement surgery (arthroplasty) involves removing damaged joint surfaces and replacing them with plastic and metal parts.

Lifestyle and Self-Care
Lifestyle changes are critical for managing osteoarthritis. Exercise, specifically low-impact activities like swimming, walking, or biking, increases endurance and muscle strength around the joint. Weight loss is highly effective for relieving pressure on weight-bearing joints like the knees and hips. Using hot and cold packs can relieve pain and stiffness. Assistive devices, such as canes, shoe inserts, or gripping tools, can help reduce stress on joints and improve independence.

When to Seek Medical Care
You should see a doctor if you experience joint pain or stiffness that does not go away or interferes with daily activities. Immediate medical attention is required if joint pain is accompanied by redness, warmth, or a fever, as these may be signs of an infection rather than osteoarthritis. Routine follow-up is recommended to monitor the progression of the disease and adjust pain management strategies as needed.

Disease Severity and Progression
Osteoarthritis is a progressive disease, meaning it typically worsens over time, although the rate of progression varies widely among individuals. It ranges from mild forms, where symptoms are a minor nuisance, to severe forms where the loss of cartilage leads to bone-on-bone friction. Factors that influence progression include body weight, activity level, and history of joint injury. While the damage to joints cannot be reversed, treatment can significantly slow progression and improve joint function.

Complications and Long-Term Effects
Chronic pain and stiffness can lead to complications that affect overall health. Severely painful knees or hips can make it difficult to walk, increasing the risk of falls and injuries. Reduced mobility often leads to weight gain, which can worsen the arthritis and increase the risk of other conditions such as diabetes and heart disease. The breakdown of cartilage affects the joint's mechanics and can lead to misalignment of bones and deterioration of ligaments.

Prognosis
The prognosis for osteoarthritis depends on which joints are affected and the severity of symptoms. It does not directly affect life expectancy, but the sedentary lifestyle resulting from pain can contribute to other health risks. With early diagnosis, weight management, and physical therapy, many individuals maintain an active lifestyle and delay the need for surgery. Joint replacement surgery, when necessary, has a high success rate in restoring function and relieving pain for severe cases.

Daily Activities and Function
Osteoarthritis can interfere with work and daily routines, making tasks like gripping objects, climbing stairs, or standing for long periods challenging. Patients often need to pace themselves, alternating periods of activity with rest to avoid overstressing the joints. Simple modifications, such as using a raised toilet seat or wearing shock-absorbing footwear, can make daily living easier. In the workplace, ergonomic adjustments like specialized chairs or keyboards can help reduce strain.

Mental and Emotional Health
Living with chronic pain can take a toll on mental health, leading to frustration, anxiety, or depression. The limitations on mobility may lead to social isolation or a loss of independence. Developing coping strategies is essential; this may include joining support groups to connect with others facing similar challenges or practicing relaxation techniques like meditation to manage pain perception.

Questions to Ask Your Healthcare Provider
Preparing a list of questions can help you get the most out of your medical appointments. Consider asking:

• What specific type of arthritis do I have and which joints are affected?
• Is there any damage to my bones or just the cartilage?
• What exercise or physical therapy routine do you recommend for my specific condition?
• Are there medications that can help manage my pain with minimal side effects?
• How will we monitor the progression of the disease over time?
• At what point should we consider surgical options like joint replacement?

Q: Is exercise bad for my joints if I have osteoarthritis?
A: No, exercise is generally good for osteoarthritis. Low-impact activities help strengthen the muscles that support your joints, which acts as a shock absorber. However, you should avoid high-impact activities that pound the joints and stop if you feel sharp pain.

Q: Does cracking my knuckles cause osteoarthritis?
A: There is no scientific evidence that cracking knuckles causes osteoarthritis. The sound is caused by gas bubbles bursting in the fluid surrounding the joint, not by bones rubbing together.

Q: Can the weather really affect my arthritis pain?
A: Many people report that their joint pain worsens with cold, rainy weather or changes in barometric pressure. While the exact reason is not fully understood, it is a common real-world observation, possibly due to pressure changes affecting joint tissues.

Q: Is osteoarthritis hereditary?
A: Genetics can play a role. If your parents or siblings have the condition, you are more likely to develop it. Certain genetic defects affecting cartilage or joint fit can also be inherited.

Q: Is there a cure for osteoarthritis?
A: Currently, there is no cure that can reverse the damage of osteoarthritis. Treatment focuses on managing pain, improving function, and slowing the progression of the disease.