ARTHROSCOPIC KNEE PROCEDURES
There are many conditions of the knee that can be dealt with using an arthroscope.
An arthroscope is a solid glass lens which is inserted through a small incision into the knee.
The arthroscope is attached to a camera which in turn is attached to a monitor to allow the operation to be viewed on a screen. The camera is used to obtain images to record the operation.
The term “keyhole surgery” has been used to popularise this type of operation.
Through the arthroscope, fluid, typically saline, is used to fill the knee to allow structures within the knee to be seen.
Using typically three incisions many common knee problems can be dealt with as described below.
Each knee contains two menisci. In lay terms these are often referred to as “cartilages”.
There is one on the inner (medial) portion of the knee and one in the outer (lateral) half of the knee.
Each meniscus is prone to damage through injury. They may also deteriorate as part of the process of aging.
Injuries to the menisci can present with a variety of symptoms.
Typically the patient will develop pain along the inner or outer side of the joint according to which meniscus is damaged.
There may be a history of a twisting injury or a significant application of force, for example during a tackle, to the affected knee.
Pain can radiate up and down the inner and outer aspects of the knee, as well as through to the back of the knee.
Patients may experience difficulty in their ability to straighten (extend) their knee and may describe the knee as feeling “locked” as if something is blocking their ability to extend the knee.
Injuries to the menisci vary in their severity.
A truly ‘locked” knee is often the result of a “bucket-handle” tear of the meniscus either medial or lateral.
The torn portion of meniscus flips in and out of position producing the “locking” symptoms. This produces spasm and pain.
When the torn portion is not displaced then the individual may be asymptomatic.
Other tears may be described as “cleavage”, “horizontal” or “fish-mouth”. These produce symptoms of pain along the joint line, radiating through to the back of the knee.
The symptoms vary in their intensity and are often worse with activity.
Each meniscus has a limited blood supply which it receives from its attachments to the edge of the knee joint.
As a result tears of the meniscus have a limited ability to heal.
Only tears in the region where the blood supply is good (a peripheral detachment) have a good ability to heal. Such tears may be repaired and have a good chance of healing.
The remainder will usually result in a portion of the meniscus being removed.
Each knee joint is covered in a highly specialised layer of cartilage. This is known as articular hyaline cartilage.
Normally this surface allows smooth movement of the two bones over each other. The cartilage also absorbs the normal loading that occurs with daily activities and acts as a cushioning surface.
During an acute injury or as a result of chronic degeneration (osteoarthritis) this surface becomes damaged and the cartilage roughens.
This can sometimes produce a crackling sound or sensation and may result in local irritation.
As a result of cartilage deterioration the knee itself can become swollen.
This occurs as the joint lining (synovium) produces increased amounts of synovial fluid to try and lubricate the knee. These fill the knee causing distension, discomfort and pain.
This is known as an effusion.
These rough areas of articular cartilage can be smoothed by using an arthroscopic “shaver” introduced through one of the portals during an arthroscopy. This smoothes the roughened areas, leaving a smoother articulating surface, thus reducing the local irritation.
In these cases attempts are made to promote new cartilage formation in the damaged area. This is done by breaking through the exposed bone.
This process is known as Microfracture.
A sharp pointed awl is introduced through one of the portals and used to puncture the bony surface in several places in the effected area.
The bleeding bone surface produces a blood clot that adheres to the effected area.
This clot is invaded by cells which form a cartilage scar.
This new cartilage is called fibrocartilage and forms a new smooth surface. This reduces the symptoms. The fibrocartilage is not the same as the specialized hyaline cartilage and lacks its properties.
Removal of Loose Bodies
A piece of bone or cartilage can be broken off during an injury or as part of a more general degeneration and form a 'loose body' within the knee.
Loose bodies can remain symptomless for long periods but can cause sudden attacks of pain and locking.
Usually the locking is only momentary and the individual states that they can work the knee free.
Occasionally individuals will complain that they can physically feel the loose body within the knee and isolate it at certain times.
Loose bodies can be removed at arthroscopy although they often require a slightly larger incision depending upon their size.
Medial Plica Syndrome
Patients may complain of pain along the inner aspect of the knee in relation to the side of the knee cap (patella) or behind the knee cap.
At arthroscopy this tissue is easily removed with a shaver.
After the procedure the patients will require rehabilitation with a physiotherapist.
This can be done using scissors or a device which cauterizes the tissue at the same time. The instances and indications for a lateral release are limited with strict indications.
Typically the patella in such patients is tethered and tilted and on visual inspection with the arthroscope does not sit normally in its groove on the front of the thigh bone throughout the normal range of movement of the knee.
Often this can only be fully determined at the time of surgery although appropriate pre-operative x-ray investigation will be suggestive that it is required. Following lateral release patients will require extensive physiotherapy rehabilitation.