Description of Knee Osteoarthritis
To understand osteoarthritis of the knee, it is important to understand the conditions of a healthy knee.
Osteoarthritis forms when there is damage to the articular cartilage. The articular cartilage is the “gristle” at the end of the femur, tibia, and patella. The synovial fluid in the knee and articular cartilage at the end of the bones, combine to create a frictionless surface within the joint. In addition, articular cartilage allows for the absorption of forces, which is especially important for participants in high-impact activities.
It is well known that once there is articular cartilage damage, the body does not have the capability to heal naturally. Where there is articular cartilage damage, even just slightly, it initiates the process of further deterioration of articular cartilage surface over time. Thus, any damage to the articular cartilage surface is osteoarthritis.
Osteoarthritis is usually graded as different forms of chondromalacia (wearing down of the cartilage surface):
- Grade 1: early articular cartilage damage to the surface and softening
- Grade 2: pitting and fissuring of the cartilage surface
- Grade 3: articular cartilage damage with fissuring down to the bone
- Grade 4: complete wear of the cartilage surface and exposed bone
The inevitable effects of grade 4 chondromalacia are primarily seen on x-rays. Because there is no existing gristle between the bones, the bone surfaces can be directly opposed against each other. This is known as bone-on-bone arthritis. In addition, there can be bone spurs (osteophytes), increased hardening of the bone around the area of the arthritis (sclerosis), and a squaring of the bone surfaces at the knee joint, rather than the normal rounded surface.
Symptoms of Knee Osteoarthritis
The usual clinical signs of osteoarthritis are pain and swelling with activities. This is because the cartilage surfaces are damaged and any impact activities can cause further wear of the surfaces. Loose bodies, which consist of small chunks of cartilage wear or broken off bone spurs, can float in the knee and cause the joint to become very irritated.