Knee pain can be caused by multiple conditions and may not necessarily be arthritis. If you have knee pain or mobility issues, see a specialist to determine whether it may be caused caused by a simple overuse condition such as runner's knee or whether you are experiencing the onset of osteoarthritis.
The knee joint can be thought of as a hinge joint, with the primary motion of bending and straightening. In reality, it is more complex than a simple hinge, as these surfaces actually glide and roll upon one another. Three bones meet to form the knee joint: the femur (thighbone), the tibia and the patella (kneecap). The bones are covered with smooth cartilage surfaces that act as a cushion during weight-bearing activity.
The bones of the knee are covered with a smooth, glistening layer called articular cartilage and connected by strong ligaments and powerful muscles that are attached to the thigh and calf by tendons, and which provide side-to-side stability. In a healthy knee, all of these structures work together to allow the knee to flex (bend) and extend (straighten) the lower leg smoothly.
The knee can be thought of as having three compartments: the medial (inner), the lateral (outer) and the patellofemoral (where the patella or kneecap meets the femur). In addition, there are two specialized types of cartilage within the knee joint called the lateral and medial meniscus. These act as shock absorbers within the knee joint. Two ligaments – the anterior cruciate ligament (ACL) and the posterior cruciate ligament (PCL) – contribute to the knee's stability.
Knee arthritis literally means "inflammation of the knee joint," most often as a result of cartilage in the joint wearing down to a degree where it no longer cushions the surfaces of bone which make up the joint. Damaged cartilage causes a roughened joint surface and may lead to bones rubbing directly together. This causes persistent pain, clicking, a catching sensation, and limited range of motion. Healthy articular cartilage can be seen on X-ray as a pronounced spacing between the bones. On an X-ray of a knee with arthritis, this space is reduced or, in some places, even absent due to worn cartilage.
There are two basic types of knee arthritis, and they have separate causes. Osteoarthritis, also known as degenerative joint disease is the most common type. This is a slow, progressive in which the articular cartilage of the femur, tibia, or patella wears down over time. It affects most people at some point as they age, usually in their 60s or 70s. Inflammatory arthritis is an autoimmune disorder that may cause inflammation in multiple joints at the same time and may affect young or old people alike.
In a person with knee osteoarthritis, the normally smooth surfaces of the joint becomes roughened and may cause increased pain, stiffness, and limited motion. Although it is most common in older people, younger patients may get post-traumatic arthritis. This is a form of early onset osteoarthritis that results from an injury to the ligaments, cartilage and/or bone in or around a joint. This causes instability that increases the wearing down of cartilage surfaces.
Symptoms include knee joint aching, soreness and pain, and swelling and stiffness. Sometimes this leads to reduced activity and muscle weakness. Weakened muscles can lead to instability and decreased ability to control the knee, further limiting the ability to participate in enjoyable activities. The knee joint may develop cysts, bone spurs, or loss of cartilage. The absence of cartilage will cause friction and narrowing of the joint space.
The loss of the gliding surfaces of the cartilage may make people feel as though their knee is stiff and their motion is limited. Sometimes people actually feel a catching or clicking within the knee. Generally, loading the knee joint with activities such as walking long distances, standing for long periods of time, or climbing stairs makes arthritis pain worse. When the arthritis has gotten to be severe, the pain may occur even when sitting or lying down. The pain is usually felt in the inside part of the knee, but also may be felt in the front or back of the knee. As the cartilage is worn away preferentially on one side of the knee joint, people may find their knee will become more knock-kneed or bowlegged.
Generally, loading the knee joint with activities such as walking long distances, standing for long periods of time, or climbing stairs makes arthritis pain worse. When the arthritis has gotten to be severe, the pain may occur even when sitting or lying down. The pain is usually felt in the inside part of the knee, but also may be felt in the front or back of the knee. As the cartilage is worn away preferentially on one side of the knee joint, people may find their knee will become more knock-kneed or bowlegged.
Knee arthritis symptoms can can vary. In rheumatoid arthritis, knee pain usually worsens after periods of rest and inactivity as joints stiffen. Some may experience pain, swelling, redness and warmth, especially in the morning.
The likelihood of arthritis increases with a family history and advancing age. Patients who are overweight and those who have undergone trauma to the knee joint may also experience early wearing of cartilage.
If you have been diagnosed with osteoarthritis, having an affected knee does not mean that you will develop arthritis in the opposite knee. About 40% of patients who have osteoarthritis in one knee will have the same condition in the other knee. In contrast, patients with rheumatoid arthritis often develop problems in both knees.
Osteoarthritis of the knee may be treated by a sports medicine physician or an orthopedic surgeon, depending on your particular condition. A physical therapist may be able to treat less severe cases to help reduce pain and increase your mobility. If your knee pain is a result of rheumatoid arthritis, gout or other form of inflammatory arthritis, you should consult a rheumatologist. (Find a doctor who diagnoses and treats knee arthritis.)
An accurate diagnosis for knee arthritis relies on three elements:
Your doctor will ask about your medical history and symptoms, and then conduct physical exam to assess:
If the physical exam suggests you may have knee osteoarthritis, various types of radiological imaging exams may be used to confirm the diagnosis and determine the level of joint degeneration.
X-rays are very helpful in diagnosing advanced knee osteoarthritis because the joint will have specific characteristics, including:
Although it may seem counterintuitive, walking can help decrease the pain and stiffness associated with osteoarthritis. In addition, any form of exercise that helps you maintain a healthy weight can reduce the stress on your joints, and this may slow the progression of your arthritis. You should, however, consult a doctor to confirm that your knee pain is caused by osteoarthritis rather than by an injury for which resting would be appropriate. A physical therapist can help determine appropriate levels of exercise for patients with osteoarthritis of the knee.
Physical therapy often does help in early stages of arthritis of the knee. An orthopedic doctor or physical therapist can teach you some of these exercises, which focus upon strengthening the quadriceps muscle.
Nonsurgical methods to relieve pain and stiffness should are usually tried first. These may include physical therapy, and/or oral pain medications or injections of corticosteroid or other agents. Inflammatory arthritis in the knee is usually managed medically rather than surgically. For osteoarthritis, and advanced case knee arthritis, knee replacement surgery (whether total or partial) is common, although other surgeries may be appropriate for certain cases.
It is difficult to predict the timing and progression of knee arthritis. Sometimes, pain increases and the ability to participate in daily activities decreases despite nonsurgical treatment plans. In those cases, surgery may be recommended.
Although knee replacement for arthritis is the most common and well-known surgery, other procedures may be appropriate for some patients. A knee osteotomy, for example, can help some patients who have a rotational or alignment issue that is accelerating the development of osteoarthritis. Others may benefit from a synovectomy and/or some type of knee arthroscopy.
Various surgeries may be appropriate, either on their own or in combination with another.
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