Anatomy of the Knee
Your knee is a hinged joint in which three bones meet: the femur, tibia, and patella (knee cap). It is one of the major weight bearing joints of the body. The ends of the bones and all the joint surfaces that come in contact with one another are covered with a smooth substance called articular cartilage. Articular cartilage cushions the bone during weight bearing and allows the bones to glide smoothly during knee motion without pain.
Description of Knee Arthritis
If the articular cartilage covering of the knee begins to break down or wear away, this process and the subsequent synovitis (inflammation of the joint lining) it causes is called arthritis. There are 3 main types of arthritis that affect the knee:
- Osteoarthritis (OA) is the most common form of arthritis. OA is usually a slow, progressive degenerative disease in which the joint cartilage gradually wears away. It often affects middle-aged to older people and is also called degenerative arthritis.
- Rheumatoid arthritis (RA) is an inflammatory type of arthritis that can destroy the joint cartilage. It is an autoimmune process in which the body can attack its own cartilage. RA can occur at any age and generally affects multiple joints.
- Post-traumatic arthritis can develop after an injury. This type of arthritis is similar to osteoarthritis and may develop years after a fracture or ligament injury.
Causes of Knee Arthritis
Development of knee arthritis can be caused by many different factors, and while these factors can affect RA as well, most of the following information is more specific to OA .
- Trauma/injury – A history of trauma to the knee joint can play a large role in the development of athritis, especially a fracture, an injury to the meniscus, a tear in a stabilizing knee ligament, or a direct injury to the articular cartilage.
- Weight - Body weight plays a key factor in the development and progression of arthritis, as an increase in body weight is directly related to the amount of forces seen across the knee joint with weight bearing activity.
- Alignment - Any misalignment of the knee joint (e.g. bow-legged or knock-kneed alignments) can accelerate the rate of arthritis in one compartment of the knee.
- Genetics - Some people have articular cartilage that is not as durable and they may develop arthritis at a younger age.
Typically, pain associated with arthritis develops gradually. However, some patients develop “silent” arthritis for years before they have a sudden onset of joint pain. It is believed that these patients do not experience pain during the initial breakdown of cartilage, but as cartilage destruction worsens the pain can suddenly develop. The joint may become stiff and swollen, making it difficult to move the knee. With most forms of arthritis, pain may increase after activities such as walking, stair climbing or kneeling. The pain may often cause a sense of weakness resulting in “buckling” or “giving-way”. Many people also report an increase in their pain with fluctuations in the weather.
Your surgeon will take a detailed medical history and will focus on any previous history of injuries or surgeries to your knees. You will be asked many questions about the quality, severity, duration, and timing of your symptoms – especially regarding pain and stiffness. Any family history of RA or other inflammatory conditions will also be explored.
During the exam, it will be important to watch you walk to examine your gait. Your knees will be examined for alignment, tenderness, effusion (swelling), range of motion, crepitus (popping or cracking noises), stability, and strength. Both knees will generally be examined even if only one is symptomatic.
Perhaps the most important test in diagnosing arthritis is a good set of weight bearing X-rays. Cartilage wear is reflected on X-rays by loss of joint space. The hallmark of advanced arthritis is osteophyte, or “bone spur”, formation at the edges of the affected joint space. These spurs, when small, do not cause much pain themselves but are the body’s reaction to cartilage breakdown. Usually, more advanced imaging tests such as CT or MRI are not needed if arthritis is the primary diagnosis.
Blood and other special imaging tests may be needed to diagnose RA or other inflammatory or autoimmune types of arthritis. These are typically diagnosed and treated by your Primary Care Physician or rheumatologist unless the joint destruction is severe and needs replacement.
Non-surgical Treatment of Knee Arthritis
Nonsurgical treatment options include
- Rest – Allowing the knee some time to recover from an acute flare may be beneficial in reducing inflammation inside the joint.
- Activity modification - Switching from running or jumping activities to lower impact exercises such as swimming or cycling, and minimizing activities such as climbing stairs that aggravate the condition can help control arthritis symptoms.
- Ice/heat – Cold therapy can help reduce swelling and stiffness in an arthritic knee, especially after activity. Heat may decrease pain and help loosen up a stiff joint before activity, but may contribute to increased swelling later.
- Non-steroidal anti-inflammatory medication - Over-the-counter drugs like ibuprofen and naproxen, or prescription anti-inflammatory medication can reduce pain and swelling.
- Strengthening exercises and physical therapy - Specific exercises will restore movement and strengthen your knee. Your exercise program will include stretches to improve flexibility and range of motion. Strengthening the muscles that support your knee can relieve pain and prevent further injury. Aquatic therapy may be of specific benefit because the buoyancy of the water takes stress off the knee during exercise.
- Nutritional supplements – Supplements such as glucosamine and chondroitin sulfate have received a lot of attention in arthritis treatment, but not much scientific data supports their use. However, many patients report a decrease in arthritic pain with these supplements.
- Assistive devices – A cane or a walking stick can help reduce the weight bearing stress on an arthritic knee and can decrease pain.
- Bracing – An elastic knee wrap or sleeve can help control swelling and decrease stiffness in an arthritic knee. If arthritis only affects one side of the knee (medial or lateral), then more rigid unloader bracing may be a good option to shift the alignment and the forces across the knee. This can take stress off of an arthritic knee compartment and transfer that stress to a healthier compartment.
- Steroid injection – If rest, medications, and physical therapy do not relieve your pain, an injection of a local anesthetic and a cortisone preparation may be helpful. Cortisone is a very effective anti-inflammatory medicine, but is not used on a very frequent basis due to potential negative effects on the cartilage from repeated use.
- Viscosupplementation/Hyaluronic Acid injections – “Gel shots” may help alleviate your symptoms. While not as fast acting as cortisone, these series of shots help to restore the joint fluid to its natural state and help to give the knee lubrication, which can ultimately give longer-term relief.
The disadvantages of nonsurgical treatment are:
- Activities may need to be limited
- Regular office visits for injections
- Expense and inconvenience of bracing and injections
Surgical Treatment of Knee Arthritis
Your doctor may recommend surgery (partial or total knee replacement, high tibial osteotomy) if your pain does not improve with nonsurgical methods. Continued pain that does not respond to conservative management is the main indication for surgery. There are many factors to consider when making the decision for knee replacement.
Important factors in surgical decision:
- Age – young patients are not good candidates for knee replacement unless all other options have been exhausted; the knee components have a limited life span and revision surgeries are much more complex and have higher complication rates
- Weight – body weight has a direct relationship to the lifespan of a replacement implant on a weight bearing joint such as the knee; there is no absolute cutoff but there are some patients that are too heavy to be considered for knee replacement
- Activity level – knee replacements are not designed for high-impact activities such as running, jumping, or cutting; if these sporting activities are desired then an osteotomy or brace may be a better option
- Medical comorbidities – multiple conditions such as cardiac disease, diabetes, kidney disease, etc. can make the complication risks from a knee replacement surgery outweigh the benefits
Knee Arthritis: Surgical Treatment Options
Partial (Unicompartmental) Knee Arthroplasty
In certain cases, arthritis of the knee is confined mainly to one compartment of the knee. If the other compartments of the knee are relatively normal and all of the main knee ligaments are intact, then replacing only the arthritic compartment is an excellent solution. This allows a less invasive procedure and requires less bone removal than a total knee arthroplasty. It can serve as a bridge procedure, buying a young patient 10, 15, or even 20+ years before needing a total knee replacement.
Total Knee Arthroplasty (TKA)
Knee replacement is sometimes the only solution to advanced knee arthritis. It involves cutting and capping the ends of the bones with metal and polyethylene components. This effectively removes all the native joint surfaces of the knee joint and corrects any arthritis. The metal and plastic components have a limited life span that depends on multiple factors such as alignment, body weight, bone quality, and activity level.
High Tibial Osteotomy (HTO)
In younger, active patients with one-compartment (medial or lateral) arthritic disease, realigning the limb to distribute the stresses away from the arthritis compartment is a better option than replacing the joint. This involves cutting the bone of the tibia and changing the alignment several degrees, and requires plates and screws to hold the bone in place while the osteotomy heals. This option allows young, active patients to continue with high impact activities for years before progressing to a knee arthroplasty.
Complications of Surgery
The most common complications of knee replacement surgery include
- Blood clots (DVT’s)
- Pulmonary embolism
- Anesthesia complications
- Nerve or blood vessel injury
- Malunion/nonunion/fracture (from HTO procedures)
Rehabilitation plays an important role in regaining your knee function after a knee replacement. A structured physical therapy program will help you regain knee motion and strength. Therapy will progress in stages following your surgery, and can last from only a few weeks for a partial replacement to 3 or more months for a total knee replacement. Some patients may complete their initial rehab at home with a home therapist, and then transition to outpatient therapy after 1-2 weeks. Other patients may need inpatient rehab after the surgery for more supervised therapy during the initial 1-3 weeks after the procedure, and then transition to either home or outpatient therapy.
- If I have knee arthritis and keep doing things on my knee, will this cause further damage?
Arthritis is a slowly progressive disease, but continued high impact activity may cause it to progress faster. Low-impact exercise to keep the muscles around the knee strong is important in treating arthritis, but high impact exercise is generally not advised.
- When should I see a doctor for knee arthritis?
When your pain becomes moderate to severe or limits your activity level, it may be time to see someone about your arthritis. There are many options for arthritis treatment in the early stages that don’t require surgery, so don’t just try to tough it out when there may be good ways to help alleviate your pain.
- Can knee arthritis resolve or go away with time?
The symptoms of arthritis may improve with exercise, changes in the weather, weight loss, etc. However, the actual wear and degeneration of the articular cartilage is permanent and irreversible.
- Can all knee arthritis be treated surgically?
In most cases, knee replacement can correct knee arthritis. Sometimes, in cases of severe deformity of the knee, active or multiple infections in the knee, or severe medical comorbidities may rule out knee replacement as a treatment option.
- How do I know if I need a partial versus a total knee replacement?
If your arthritis symptoms are severe enough to warrant knee arthroplasty, then the decision of partial versus total knee replacement is based on many factors including the alignment of your knee, the pattern of your arthritis, the stability of your knee ligaments, and your age. A thorough examination and a good set of X-rays will be needed to make that decision.
- What are the advantages of partial knee replacement over total knee replacement?
Partial knee replacement has many advantages over total knee replacement:
• less invasive surgical procedure
• less bone removal
• faster rehabilitation
• can be converted to total knee replacement when it wears out
- Are there any disadvantages of partial knee replacement compared to total knee replacement?
The procedure is less common and is technically more demanding than total knee replacement. If your surgeon is not very familiar with partial knee replacement then the outcomes will likely be inferior.
- How long can I get shots in my knees to treat arthritis?
As long as they help with your pain, there is really no time limit. Repeated cortisone injections may have some detrimental effects to the surrounding cartilage and knee tissues.
- Can I wait too long to have a knee replacement?
Waiting too long can cause you undue pain, and may make the surgical procedure technically more difficult for the surgeon especially if you have a progressive deformity of the knee. However, waiting as long as possible can also lessen the chances that you will need a second, or revision knee replacement at some point in your life.
- I have developed a deformity of my knee joint over the last several years, will knee replacement straighten my knee?
Yes, knee replacement can correct most deformities of the knee joint. Obviously, extremely severe deformities may not be correctible by any means.
If you have more questions, please call my office at 502-394-6341.