One of the most common disorders I see in my office (other than shoulder problems) is osteoarthritis of the knee. It is also the leading cause of disability in the US. This is a degenerative disorder that can be thought of as “wear and tear” in the joint. Many patients confuse osteoarthritis (OA) with rheumatoid arthritis (RA), but they are separate disorders. Before discussing the ins and outs of the disease, I will briefly discuss the anatomy of the knee. There is also a simple diagram below. It is helpful to think of the knee as a hinge joint between the femur (thigh bone) and tibia (shin bone). Next, imagine two types of cartilage in the knee. The first is articular cartilage, which is the protective, smooth covering at the ends of the bones. The other is fibrocartilage, which makes up the menisci (plural for meniscus), of which there are two in each knee. The menisci are the cushions or shock absorbers in the knee. It is also important to know that we think of the knee as having three compartments: medial (or the inside), lateral (outside) and patellofemoral (between the knee cap (patella) and the end of the femur) compartments. Osteoarthritis, as mentioned previously, is a degenerative process involving breakdown of the articular cartilage, joint space (or compartment) narrowing, reactive changes in the bones, and changes in the menisci over time.
Symptoms of OA include pain, occasional swelling, and stiffness, especially in the morning. These symptoms usually begin gradually but sometimes can start suddenly. Common complaints include pain after prolonged periods of walking, sensation of the knee “giving out” or buckling, and difficulty going from a seated to standing position. Patients can experience periodic episodes of worsening pain and swelling which can sometimes be attributed to a change or increase in activities. However, I find that most of the time, there is no rhyme or reason for an exacerbation. Such is the unpredictable nature of OA.
Risk factors for OA include:
Increased age (sorry, can’t do much about that)
Genetics (that either)
Gender (females > males)
Abnormal biomechanics at the knee (for example, laxity due to ACL injury or malalignment)
Overuse/work load/sports ? (not 100% sure – the literature is conflicting)
*strongest modifiable risk factors
OA can usually be diagnosed by x-ray. We can’t see the articular cartilage on x-ray, but there are some other telling signs. What I look at first is the space between the bones. If this space is decreased, it is referred to as joint space narrowing. Another sign of OA is osteophyte formation, or the formation of bony spurs at the edges of the bones. This is the bone’s way of reacting to forces through the joint. These changes can be seen in any or all of the three compartments in the knee.
Unfortunately, there is no cure for osteoarthritis, and the most definitive treatment is knee replacement. However, there are many conservative measures outside of surgery that can be utilized. These will be discussed in Part II.