What is Osteoarthritis
Osteoarthritis is a disease which initially affects articular cartilage and subsequently spreads to the entire joint. Cartilage covers the extremities of the femur, tibia and kneecap (known as the patella). This cartilage enables good joint mobility.
Cartilage is a living tissue which must remain "smooth" and "flexible" in order to fulfil its functions: as a shock absorber and facilitating sliding of the joint. Without it, bones would come into contact with one another. The joint is surrounded by an envelope, known as the synovial capsule, which helps lubricate the joint and nourish cartilage.
With age, cartilage progressively loses its ability to retain water, its flexibility and wears thin. Excess pressure on this weakened cartilage will cause it to become damaged. This will gradually cause it to disappear in some areas revealing the underlying bone.
In parallel, an onset of an inflammatory phenomenon occurs at the synovial membrane, liable to generate excess synovial fluid (known as synovial effusions). Once the bone is stripped of its cartilage and under the effect of day-to-day pressures and the local inflammatory phenomenon will progressively form bony outgrowths called osteophytes.
This can become very painful when moving the knee and impede day-to-day activities significantly, impairing quality of life.
Osteoarthritis diagnosis
Osteoarthritis can be diagnosed by your GP through a detailed patient history, physical examination and x-ray if required. The examination may involve looking at joint swelling, limitations to range of motion as well as looking at levels of pain, and impact on quality of life. It is important to note that there is no correlation between the level of pain and/or limitation felt and radiological assessment in arthritic knees.
There are certain predisposing factors, that increase the risk or likelihood of osteoarthritis:
Sex - women are more at risk
Age - over 45s are more at risk; over 70s show highest presentation
Obesity - or raised BMI
Abnormal leg alignment - often referred to as "bow legged" (varus) or "knock kneed" (valgus)
Genetics - if a parent has suffered from OA
Professions/ jobs - roles that include lots of heavy lifting, kneeling on hard floors or lots of going up and down stairs
High level sports participation - ball sports, running, skiing, etc
Previous ligament or meniscal knee injury
Suffering from another joint disease - such as rheumatoid arthritis
Osteoarthritis symptoms
The main symptoms of knee osteoarthritis are pain and stiffness, this can make it difficult to move the knee and do certain activities.
Symptoms vary from person to person but tend to gradually worsen over time, and symptoms that initially came and went may become continuous. Knee osteoarthritis often presents in one knee initially, but typically the other leg can become affected in time.
The knee is the most common joint in the body to be affected by osteoarthritis. Other symptoms typically include:
Joint tenderness
Knee appearing slightly larger, or sightly out of alignment
Crepitus: a grating or crackling sound or sensation in your joints
Limited range of movement
Weakness and muscle atrophy (decreasing muscle bulk)
Sensitivity to kneeling
Knee giving way, feeling unstable
Difficulty in going up and down stairs
Sensitivity to cold or damp conditions
Types of knee osteoarthritis
There are different types of osteoarthritis of the knee, relating to what area or areas of knee joint are affected by degeneration.
The knee is made up of three main compartments:
The patellofemoral compartment is the joint between the patella and the end of the femur.
The medial and lateral tibiofemoral compartments are the articular areas between the tibia and the femur.
The tibiofemoral compartments are the weight bearing compartments of the knee joint.
The medial compartment is the area of the knee joint closest to the midline of the body and the lateral compartment is on the outer aspect of the knee. Arthritis can affect any or multiple compartments.
The four main types are:
Medial Tibiofemoral Osteoarthritis will typically present with pain in the predominantly the medial compartment, and degeneration can lead a varus alignment, often called a bow-legged alignment.
Lateral Tibiofemoral Osteoarthritis is less common but can occur in individuals who present with a valgus or “knocked kneed” posture or in individuals who have had previous injury to the lateral structures of the knee. Lateral compartment osteoarthritis presents with pain in the outside compartment of the knee.
Patellofemoral Osteoarthritis is a presentation where there is degeneration in the compartment between the patella and the femur, typically presenting with pain at the front of the knee.
Tricompartmental Osteoarthritis is degeneration of the knee joint in all three compartments, pain is widespread in the knee and not localised to a particular part of the knee joint.