At times there is no substitute for simply looking inside of a knee joint to find and correct a problem. Knee arthroscopy is a minimally invasive technique for doing just that; it refers to a broad category of surgical procedures (typically outpatient) that involve looking within the knee joint using a fiberoptic video camera and small instruments. Knee arthroscopy is useful for the diagnosis and treatment for a number of common problems within the knee.
Indications
Many patients may have internal derangement of the knee, which refers to the knee having a problem from within that keeps it from moving and functioning in the normal manner that it should. Common symptoms include locking, catching, clicking, popping, and buckling or giving way. These types of problems are often caused by a problem within the joint, such as a loose body or a meniscal tear (commonly referred to as a "torn cartilage"). Arthroscopy is useful not only for diagnosing these problems by looking inside the knee, but also for correcting them by removing a loose piece of bone, trimming or repairing a torn area of cartilage, or removing excessive synovial lining or scar tissue.
There is a limited role for arthroscopy with arthritis. In the past, some surgeons have advocated "cleaning out" an arthritic knee (e.g., arthroscopic lavage), and in fact arthroscopy is very good at relieving mechanical symptoms such as locking even in an arthritic knee. Flushing the knee does remove inflammation, at least temporarily. .However, it cannot "cure" arthritis, and for that reason many surgeons will not recommend its use for simple arthritic changes unless there are also mechanical symptoms.
Arthroscopy also can be used to wash out an infection within the knee joint, without requiring a large incision and opening the entire joint.
Chondroplasty refers to smoothing out roughened joint surfaces or cartilage, and sometimes isolated "craters" in the joint surface can be drilled during arthroscopy to try to get them to fill in with scar tissue. These procedures are fairly quick outpatient procedures, but they may require limited weightbearing for a few weeks using crutches while the cartilage heals. Arthroscopy also may be used to visually inspect a knee to help determine the extent of arthritis and damage, particularly for helping a surgeon to determine if a patient may be best helped by a partial versus total knee replacement.
Occasionally there may be a discrete area of severe damage in the form of an osteochondral defect (see previous chapters). An isolated lesion can sometimes be treated with microfracture or arthroscopic drilling, techniques that are designed to stimulate formation of scar tissue to fill in the defect. This typically requires a period of limited weightbearing while it heals.
Meniscal tears and loose bodies are frequently seen on imaging studies such as an MRI. However, not all meniscal tears or loose bodies can be detected with an MRI, and the "gold standard" for diagnosis is to then perform a diagnostic arthroscopy. The idea of looking inside an area of the body with a camera is not limited to just orthopaedics; similar procedures include endoscopy (looking down the esophagus with a fiberoptic camera) or colonoscopy (from the other end!), and like those procedures arthroscopy is typically a short, outpatient procedure that often does not require full anesthesia and can even be performed under local anesthesia only in many cases.
Some meniscal tears are amenable to repair, but many have a "shredded" appearance or may not be good candidates for repair because of their location (some regions do not have good healing potential because of the way the blood supply is arranged). In these cases, the rough edge is resected back to a smooth, stable edge, which usually makes a significant improvement in symptoms. In past decades before fiberoptic arthroscopic instruments were available, surgeons would often remove the entire meniscus through an open procedure, but this often led to severe arthritis over the following years. Arthroscopy allows surgeons to remove just the torn portion of the meniscus, leaving as much as possible to cushion the joint.
Technique
The surgeon uses portals to insert the camera and/or instruments rather than opening the entire joint (which is called an arthrotomy). These portals are typically less than a quarter inch in size, and multiple small incisions may be used to access the entire joint. There are usually at least 2 portals, one for the camera and the other for whatever instrument the surgeon needs (such as a hook probe or a grabber to retrieve a loose fragment of bone, a mechanical shaver to trim torn cartilage, etc.).
Although full general anesthesia is sometimes used, particularly for complex arthroscopic procedures that are expected to take a while, most arthroscopic procedures are performed using a combination of local anesthetic injection and light sedation. It is similar to that used when setting fractures or having wisdom teeth extracted. Occasionally, some patients are interested and want to watch their surgery on a video screen as it is performed, and this is possible using local anesthetics for noncomplex procedures. Most simple procedures, such as trimming a torn meniscus or removing a loose body, take about half an hour or so.
During the procedure, water (saline or a mixture of salts and lactate called lactated ringers) is pumped through the camera and into the joint, then out through the same instrument or an additional outflow portal. This allows the surgeon to wash away any blood or material removed (such as resected meniscal trimmings or loose bodies). The fluid also fills the joint space so that there is plenty of space to safely work with the small instruments. Although an effort is usually made to drain the knee afterwards, some fluid remains within the joint. As a result, there may be minor drainage from the portal sites (usually closed with a single suture each or sometimes just an adhesive dressing) for a day or two, and this is not a reason for concern.
Most modern arthroscopy instruments have the capability to take photographs (shown here) or record live video of the image that is displayed on the video screen. Many surgeons will keep these photos for later reference in case the patient has any problems with the knee in the future, such as arthritic pain, and the surgeon can tell with a glance at the pictures what areas of the joint were noted to have the most arthritis or other changes.
When the procedure is complete, most patients spend a short while in the recovery room until they are fully awake and comfortable. The vast majority of arthroscopy patients go home the same day, and for this reason arthroscopy in many places may also be performed at an outpatient ambulatory surgery center as an alternative to the traditional setting of the hospital.
Arthroscopic partial meniscectomy. The torn meniscus on the left was causing significant pain and locking of the knee. In the photo on the right, the same tear has been resected back to a smooth, stable edge. |
Arthroscopic inspection of healthy structures in the knee. From top left going clockwise, these show (A) the gutters and synovial lining of the joint along the sides of the knee, (B) a normal medial compartment with intact medial meniscus and healthy joint surfaces, (C) an intact anterior cruciate ligament (ACL), and (D) a normal posterior horn of the medial meniscus (femur on top, tibia on bottom, and meniscus between). |
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Risks and Complications
Arthroscopy is a minimally invasive and outpatient procedure. As a result, complications are rare, but there are some problems that can sometimes occur that we usually warn our patients about. Anesthesia problems are uncommon but are of particular concern for patients with other medical problems (such as sleep apnea or lung disease). Infection is rare and occurs in less than 1% of patients undergoing arthroscopy, but it can be a potentially serious complication, requiring additional surgery to treat a deep infection. Infection is somewhat more of a concern for patients who have problems with their immune systems, are on immunosuppressive drugs or prednisone, or are diabetic, but even in these cases it is uncommon. Many surgeons give prophylactic antibiotics in the operating room just before the procedure to decrease this risk even further.
Blood clots, or deep venous thrombosis, are a rare complication after arthroscopy but have been reported. For that reason, many surgeons may recommend simply taking enteric coated aspirin for a couple of weeks after surgery. However, the current guidelines from the Academy and other authorities put the risk of blood clots at such a low percentage that prophylaxis is not strongly recommended on a routine basis.
Some surgeons use a tourniquet during the procedure. Because most arthroscopic procedures are fairly short, it is uncommon to have any problems from having a tight tourniquet placed for too long, although it has been reported. Similarly, although all patients have some degree of swelling after the surgery, in rare cases there can be too much swelling from having some of the saline extravasate, or travel into the soft tissues around the knee, and cause excessive swelling. When this occurs, it usually is immediately noted before leaving the operating room, and usually resolves within hours. Rarely, a problem from severe swelling called a compartment syndrome can result.
Injuries to nerves or ligaments are rare. When this does occur, it usually is a result of stretching the knee in order to get the camera and instruments into a hard to reach spot (usually the back of the knee). This can sometimes cause numbness or tingling, and rarely a footdrop (inability to flex the foot upward at the ankle). When these problems do occur, it usually is from a neuropraxia or stretching of the nerves, since they are not directly at risk for being cut, and this most often resolves in days or weeks. Also, a skin nerve called the infrapatellar branch of the saphenous nerve, which supplies skin sensation over the upper shin, is sometimes cut while placing the small incisions for the portals. It does not control any muscle function, and when this injury occurs the small area of numbness over the upper shin is usually not problematic.
Recovery And Outcomes
As noted, the vast majority of arthroscopic procedures are performed on an outpatient basis and are fairly minor procedures that take about half an hour or so to complete. Recovery and outcome depends on the exact problem being treated, but for the majority of procedures patients can expect to return to work within one to three weeks (depending on the procedure and what they do for work). Exceptions to this include more extensive arthroscopic procedures and those which require a prolonged period of limited weightbearing on crutches (such as arthroscopic drilling of a crater in the joint surface, which needs some time to allow the crater to fill in with scar tissue).
Please remember the information on this site is for educational purposes only and should not be used to make a decision on a condition or a procedure. All decisions should be made in conjunction with your surgeon and your primary care provider.
