Arthritis
Two types of arthritis can affect the knee: Osteoarthritis and Inflammatory Arthritis
Osteoarthritis, sometimes
called degenerative arthritis or degenerative joint disease, is a
condition that involves the breakdown of joint articular cartilage.
Often the cause is unknown, but osteoarthritis may develop as a result
of injury to the joint, excess body weight, or years of wear and tear
on the joint articular cartilage. As joint articular cartilage wears away, the
bone begins to make painful bone on bone contact. The early stages of
osteoarthritis can be treated with a variety of conservative,
non-surgical treatments. However, as the joint cartilage continues to
wear away and the symptoms of osteoarthritis become more severe,
surgery may be recommended to correct the damaged bone and cartilage.
SYMPTOMS
Osteoarthritis develops slowly over several years. The
symptoms of osteoarthritis are mainly pain, swelling, and stiffness of
the knee. The pain of osteoarthritis is usually worse after weight
bearing activity. Early in the course of the disease, you may notice
that your knee does fairly well while walking. Then after sitting for
several minutes, the knee becomes stiff and painful. As the condition
progresses, pain can interfere with even simple daily activities. In
the late stages, the pain can be continuous and even affect sleep
patterns.
DIAGNOSIS:
To diagnose osteoarthritis, a complete history and physical examination are performed, and a
series of x-rays are taken. On an x-ray, a healthy knee joint has a
space between the bones in the joint. Although you cannot see the
cartilage on an x-ray, in the healthy knee, the cartilage is working to
cushion and smooth the movement of the thighbone (femur) against the
lower leg (tibia) (see Figure 1). On the x-ray of a knee with osteoarthritis, there is
bone on bone contact because the articular cartilage between the femur
and tibia has been worn away (see Figures 2 and 3).
X-Ray of Healthy Knee
Figure 1
X-Ray of Knee with Osteoarthritis
Figure 2
Inflammatory or Rheumatoid Arthritis
Unlike osteoarthritis, inflammatory arthritis (rheumatoid,
crystalline, lupus, etc.) usually
affects more than one joint at a time. The affected joints have
prolifeartion of the lining of the joint (synovial membrane) and excess
joint fluid. The normal function of the synovial membrane is to
produce synovial fluid, which lubricates and nourishes joint cartilage.
There are many types of inflammatory arthritis, the most common being
rheumatoid arthritis. In rheumatoid arthritis, the synovial tissue
actually attacks articular cartilage resulting in joint destruction.
The symptoms of rheumatoid arthritis vary, but many people experience
painful joint swelling and progressively limited joint movement as the
cartilage wears away.
TREATMENT
Non-Operative Treatment
Osteoarthritis progresses slowly over a period of
many years. Osteoarthritis cannot be cured. Treatment is directed at
decreasing the symptoms, and slowing the progress of the condition.
There are a number of non-surgical treatments for osteoarthritis.
Moderate doctor-prescribed exercise and physical therapy are excellent
ways to keep affected joints moving and help relieve moderate joint pain.
Joints that are not regularly exercised become tight and painful.
Excess body weight places increased amounts of pressure on
joints. If you are overweight, weight loss may be recommended to help
relieve unwanted stress and pain on your joints. Assistive devices,
such as a cane or a walker, can help reduce the pressure placed on
joints and alleviate pain. Resting after activity can also help
control moderate joint pain.
The treatment of osteoarthritis depends on how far advanced the
condition is. In the early stages, treatment for osteoarthritis is
usually directed at decreasing the inflammation in the joint.
Anti-inflammatory medications, such as aspirin and ibuprofen, are
useful in decreasing the pain and swelling from the inflammation.
Sometimes a series of injections with a joint like fluid, a process
called viscosupplementation, will be beneficial. If the symptoms
continue, a cortisone injection may be used to bring the inflammation
under better control and ease your pain. Cortisone is a very powerful
anti-inflammatory medication, but does have secondary effects that
limit its usefulness in the treatment of osteoarthritis. The major
drawback in the use of intra-articular injections of cortisone is the
fact that it may actually speed the process of degeneration when used
repeatedly. We use cortisone sparingly, and attempt to avoid multiple injections.
There are also braces that can reduce the pressure on the side of the
knee that is most involved. These braces have been designed mainly for
the more common condition of early wear and tear in the medial
compartment of the knee. Finally, shoe inserts may be prescribed to unload the arthritic knee.
Arthroscopy
Arthroscopy may be useful in the treatment of osteoarthritis of the
knee. Arthroscopy allows the surgeon to debride the knee joint.
Debridement consists of: cleaning the joint of all debris and loose
fragments and thoroughly irrigating the knee. During the debridement, any
loose fragments of articular cartilage are removed, and the knee is washed with a
saline solution. Debridement of the knee using the arthroscope can
sometimes afford temporary relief of symptoms of pain and catching.
Proximal Tibial Osteotomy
Osteoarthritis affects the inside half (medial compartment) of
the knee more often than the outside (lateral compartment). This can
lead to the lower extremity becoming slightly bow-legged, or in medical
terms, a genu varum deformity. The result is that the weight bearing
line of the lower extremity moves more medially (towards the medial
compartment of the knee). (It's really all in the physics/biomechanics
of the situation.) The end result is that there is more pressure on the
medial joint surfaces, which leads to more pain and faster
degeneration.
In some cases, re-aligning the angles in the lower extremity can result
in shifting the weight-bearing line to the lateral compartment of the
knee. This, presumably, places the majority of the weight-bearing force
into the healthier (lateral) compartment of the knee. The result is to
reduce the pain and delay the progression of the degeneration of the
medial compartment.
The procedure to realign the angles of the lower extremity is called a
Proximal Tibial Osteotomy. In this procedure, a wedge of bone is
removed from the lateral side of the upper tibia. This converts the
extremity from being bow-legged to knock-kneed. This procedure is not
always successful, and generally will reduce pain, but not eliminate it
altogether. The advantage to this approach is that very active people
still have their own knee joint, and once the bone heals there are no
restrictions to activity level.
The Proximal Tibial Osteotomy in the best of circumstances is only a
temporary solution. It is thought that this operation buys some time
before ultimately needing total knee replacement. The
operation usually lasts for 5-7 years if successful.
Total Knee Replacement
The ultimate solution for osteoarthritis of the knee is to replace the
joint surfaces with an artificial knee joint. The decision to proceed
with a total knee replacement is usually considered in people over the
age of 60, (although younger patients sometimes require the surgery
simply because no other acceptable solution is available to treat their
condition). The main reason orthopaedic surgeons are reluctant to
perform knee replacement on younger individuals, is that the younger
the patient, the more likely it is the artificial joint will wear out.
Replacing the knee the second and third time is much harder and less
likely to succeed.
Artificial knee joints last about 10 years in an elderly
population. Younger patients are more active and place more stress on
the artificial joint. This can lead to loosening and failure earlier.
Obviously, younger patients are also more likely to outlive their
artificial joint, and will almost surely require a revision of the total knee at some
point down the road.
The Knee Replacement Procedure
Total knee replacement (TKR), also called total knee
arthroplasty, uses metal alloy and polyethylene (plastic) components to
resurface the bones in the knee joint. The implants are designed to
re-create the shape of the bones in a healthy joint.
The end of the thighbone (femur) can be compared to a rocking chair. It
has two distinct surfaces, or rockers, that contact the top of the
shinbone (tibia). Each rocker is called a condyle, and there are two
condyles at the end of the thighbone. In a TKR, the femoral component
re-creates each rocker on the end of the thighbone. The top of the
tibia is covered with a metal tray that is used to support a
polyethylene plastic bearing (see Figure 4). The polyethylene acts as the joint's
cartilage, absorbing stress and providing smooth movement. The Patellar
articular surface may or may not be replaced. If replaced, a
polyethylene insert on the back of the kneecap also provides smooth movement
against the femoral component.
Healthy Knee
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Arthritic Knee
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Figure 3
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After Surgery
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Knee Implant
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Figure 4
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