Knee osteoarthritis.

Osteoarthritis (OA) is the most common form of arthritis and is a chronic condition characterized by the breakdown of the joint’s cartilage , subchondral bone, synovial tissue and soft tissue structures around the joint. OA may occur in any joint, but the knee is one of the most commonly affected. The post will cover current concepts in regards to the causes, history, risk factors, diagnosis and treatment of the knee OA.

The pathogenesis of OA is not well understood but it likely involves local mechanical, systemic, genetic and environmental factors. Of the three joint compartments that combine to form the knee joint, the medial tibiofemoral compartment is the most common site of knee OA, presumably as a result of the majority of load being placed on this compartment.

The most important risk factors for incident OA include ageing,  congenital and developmental abnormalities, joint injury, (occupational) physical activity,  and obesity. Important risk factors for OA progression include malalignment, muscle  weakness, and obesity.

Clinically OA is characterised by joint pain, stiffness, limitation of movement, crepitus and occasionally effusion and other signs of inflammation. Joint pain is usually less in the morning and worse in the evening after a day’s activity. Joint stiffness occur after periods of rest and goes away quickly when activity resumes. Joint soreness may be present after periods of overuse or inactivity. Effusion usually occurs due to joint overload.

Diagnosis is based on patient’s history, medical examination and X-ray pictures that may show joint space narrowing, marginal osteophytes, subchondral bone sclerosis and cysts.

Existing treatment options are directed to prevent progression and reduce symptoms. These include non-surgical (non - pharmacological and pharmacological) and surgical interventions.

Non-pharmacological approaches include combination of education, lifestyle advices including regular physical activity, advices aiming for weight reduction in case of obesity and exercises directed  to improvement of muscle strength and range of motion. Pharmacological treatment  options are paracetamol, NSAIDs, weak opioids and injection therapy. Surgical options include total joint replacement and other surgical approaches, like osteotomy and unicompartmental knee replacement.