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.
Treatment of Knee Osteoarthritis
The most important thing in treating osteoarthritis in the knee is to identify it is there and to try to determine its cause. One should specifically avoid activities that cause symptoms, such as pain or swelling with activities, because the symptoms indicate that the arthritis is becoming worse. In general, we recommend light-impact activities – continuing to actively participate in these light impact activities has been proven to be very beneficial to the knee– and in some cases unloader bracing, injections, and potentially surgery will be required. While one associates total joint replacement as a common consequence of knee osteoarthritis, most patients with arthritis can hold off on joint replacement or avoid it altogether by following a proper rehabilitation program.
In addition, knee osteoarthritis surgery can be performed arthroscopically to clean out the irritated joint lining, to trim out any areas of meniscal tearing, to smooth off the cartilage surfaces, and to remove any bone spurs that may be impeding knee motion. In these cases, following a proper postop physical therapy regimen is essential for the best chance at a good outcome.
The physical therapy program for patients who have surgery to remove intra-articular scarring, bone spurs, and unstable cartilage or meniscal flaps is started on the first morning after surgery. The initial goals for this surgery are to restore muscle activity, to maintain the improved motion gained in surgery, and to try and minimize joint swelling after surgery. It usually requires patients to be on crutches, but full weight bearing, for a week. In addition, patients should avoid any aggressive strengthening exercises for the first 6 weeks after surgery. This is because scar tends to form in response to stress and usually within the first 6 weeks after surgery.