Knee Arthritis and Replacement
Written by Tom Eickmann, MD
About Knee Arthritis and Replacement
What is Knee Arthritis?
Arthritis is a lack of articular cartilage on the surfaces of the knee. This can happen from osteoarthritis, after trauma, or inflammatory conditions like rheumatoid arthritis.
Symptoms of Knee Arthritis
Arthritis can result in pain and swelling and gradual loss of function. When a patient comes to see an orthopedic surgeon they have generally already tried other treatment options.
Knee Arthritis Treatment Options
Treatment options include avoiding running and jumping, weight loss, anti-inflammatory medication, and injections. Physical therapy and bracing are also considered for specific situations. When these treatments fail to provide adequate relief and arthritis interferes with activities of daily living, knee replacement is considered as a treatment option. In the orthopedic surgeon’s office, X-rays are used to see the arthritis.
Total Knee Replacement
A knee replacement is a procedure that removes worn surfaces of the bones that make up the knee joint and resurfaces them with metal and plastic. All of the parts that come in contact with each other are covered with an artificial surface. During knee replacement, the joint is opened by sliding the knee cap over.
A small amount of bone and whatever cartilage remains is removed from the surface of the femur or thigh bone and this is replaced with a metal femoral component. A small amount of tibia or shin bone is also removed and replaced with a metal tibial component. The metal components are held in place with bone cement or an interference fit called press fit. The ACL is removed if still present. The PCL is sometimes removed depending on an individual surgeon’s preferences.
The knee cap is also resurfaced and replaced with a polyethylene patellar component in many cases, depending on individual surgeons’ preferences. The tibial component and femoral component are held apart with polyethylene that snaps into the tibial component. An injection is typically given in the area to control pain after surgery and the incision is closed with a suture and the skin is usually glued or stapled back together.
Partial Knee Replacement
Also known as a unicompartmental knee replacement, this procedure is an option for patients who have osteoarthritis that is isolated to one compartment of the knee. A partial knee replacement is recommended for patients who are no longer receiving relief from conservative treatments. This procedure can be done through a smaller incision and involves replacing only the inside (medial, outside (lateral), or patellofemoral portion of the knee.
This operation preserves the healthy bone within the joint, it is an option for patients with localized osteoarthritis of the knee. The procedure recovery is slightly faster than for a total knee. The main advantage of the procedure is gaining more range of motion after surgery. For younger patients, it also preserves bone stock for procedures down the road.
The disadvantage of the operation is it tends to not last as long as a total knee replacement. The decision to proceed with a partial knee replacement can be made prior to surgery based on the X-rays or an MRI scan. However, the final judgment to perform a partial or total knee replacement will be made by the doctor at the time of surgery depending upon the severity of arthritis of each individual compartment within the knee joint.
Revision Total Knee Replacement
Revision knee replacement is a surgery that is done involving the implants of a previously replaced knee. Occasionally due to wear, old age, complications, implant loosening, infection, instability, and stiffness implants require revision surgery. This involves taking out the involved implants and replacing them with new implants. Typically when this is done, there is some bone damage and a stem is placed on the tibia or femur for additional stability. There are varying levels of implant constraint that can be used to substitute for ligamentous or capsular insufficiencies. The outcome from revision surgery is generally satisfactory, but generally not as good as for first-time or primary knee replacements.
Implant Materials
The femoral components in most cases will be made of a cobalt chromium metal alloy. The tibial component is sometimes made of a cobalt chromium alloy or sometimes made from a titanium alloy. The cobalt chromium alloy does contain small amounts of nickel as well. The patellar component and the polyethylene cushion that rests between the femoral and tibial metal surfaces are made of a polymer which is ultra-high molecular weight polyethylene. In rare cases, cobalt chromium alloys are avoided for the tibial component and femoral component and ceramic coatings or titanium alloy components are used.
What You Can Expect
Exposure and Minimally Invasive Surgery
The incision length will depend on the amount of fatty tissue in the front of the knee. Generally, an incision between 4 and 8 inches is used. Due to variation between patients, surgery may be done through multiple approaches. A medial parapatellar approach where the quadriceps tendon is split on the medial side, a midvastas approach where the VMO is split, or a subvastas or quad sparing approach where minimal cutting of the quad is performed can be used for surgery.
Not all surgeons perform every approach, surgeons will generally use an approach that allows them adequate visualization and access to the knee with minimal trauma to the extensor mechanism. This will result in the best outcome for the patient. Ultimately what matters is that quadriceps function returns rapidly after the surgery allowing early weight-bearing regardless of which technique the surgeon prefers.
Expected Outcome
Knee replacement is a great procedure for relieving pain and restoring function for patients with osteoarthritis or rheumatoid arthritis. As patients get limited in terms of the activities that they can do like walking, hiking, and stair climbing, a knee replacement becomes a more attractive option to allow the patient to do these things again with less pain and greater function.
There is a spectrum of different outcomes from knee replacement. An excellent outcome would be patients forgetting that they even had knee replacement after full recovery. A good outcome is the most common after surgery where the patient is aware of the knee replacement but isn’t really limited or bothered by their knee. A fair outcome after surgery is less common and results in the patient still having pain and loss of function after surgery. These patients are still glad they had the surgery and are better off than before surgery. A poor outcome is uncommon and is when the patient feels the surgery didn’t help them or made them worse even after full recovery.
Knee replacement does not generally improve kneeling pain. Knee replacements often make painless clicking sounds that take time to get accustomed to hearing. Running is not permitted after knee replacement. Activities like golf, tennis, pickleball, biking, walking, and hiking are generally well tolerated after surgery.
Frequently Asked Questions
What possible complications may occur from my procedure?
As with any operation, there is always the possibility of complications. A knee replacement surgery provides many benefits to our patients who undergo the procedure, but there is a low risk of a complication. Before surgery, the risks of surgery will be discussed and written out in a consent form that is signed. Some of the possible complications include infection, bleeding, blood clots, nerve damage, fracture, and post-operative stiffness of the joint can occur. Almost all of the potential complications that can occur after or during surgery are correctable.
The most common complication after knee surgery is the development of a blood clot in the leg, or a deep vein thrombosis (DVT). Most patients are placed on aspirin or another blood-thinning medication after surgery that decreases this risk. However, if a DVT does occur, additional medication will be given to treat the clots. The national rate of infection after a joint replacement is less than 1%. If an infection does occur after surgery, it can be present in the skin layer only or, in more serious cases, deep into the knee joint itself. Nerve injury involving the lower leg occurs in less than 1% of patients who undergo knee replacement. A small nerve that runs across the front of the knee must be cut in order to gain access to the joint. Initially, this will result in some numbness around the outside of the knee which will diminish over time until it typically becomes smaller than a quarter in size. A fracture of one of the bones involved in the surgery occurs in less than 1% of patients. This complication has been seen more frequently in revision total knee replacements. If a fracture does occur, further surgery may be required. In rare cases, a brace may be required and the knee placed in an immobilizer for tendon or ligament damage during surgery.
The above information briefly covers the most common complications that can occur after a knee replacement. This is not all of the possible complications, and other risks involved in the procedure will be discussed prior to surgery. At Orthopedic Centers of Colorado, we believe it is important that the patient is well-informed in regards to the risks, benefits, and expectations of the operation. This is just one of the ways we are able to provide individualized care that results in the best possible outcome.
Will you use anesthesia for my knee arthritis & replacement?
Spinal anesthesia is typically used for knee replacement surgeries. For certain circumstances, general anesthesia will be required. There are other blocks like adductor canal blocks, femoral nerve blocks, and posterior blocks that anesthesiologists perform to help with pain after surgery. Surgeons often also perform pain blocks inside the knee as well during the surgery. After surgery, patients are given pain medications to help control their pain.
What tools and techniques are used for knee arthritis and replacement?
There are a number of different techniques to try to optimize the angle of the bone cuts during surgery. CT scans or MRI scans can be performed allowing the creation of custom instrumentation for the surgery or to facilitate the use of a robot. Computers or robots can also be used by the surgeon by inputting certain landmarks during surgery which give information back on the placement of the tibia and femoral components. These techniques generally lead to a more precise radiographic alignment of the femur and tibia, however, these techniques have not resulted in better clinical outcomes for patients in most studies. Their use is controversial amongst orthopedic surgeons and more information will be given at the surgeon’s office on their technique of choice.
