Arthroscopy is a surgical technique used by orthopedic surgeons. It involves the insertion of an arthroscope inside a joint like the knee or shoulder. The arthroscope is about the size of a pen and is inserted into the knee through a small one quarter inch incision. A tiny camera and very bright biber optic libht on the end of the arthroscope enable the surgeon to look inside the knee and visualize places that would otherwise be impossible to see.
Pictured below is the typical arthroscope.
The tip of the arthroscope is inserted into the knee joint. A powerful fiber optic light source brightly illuminates the inside and the image is projected onto a television screen. Pictured below is the typical television screen set-up.
There are many different reasons why your orthopedic surgeon may recommend a knee arthroscopy. The most common are:
- meniscal tear ( commonly referred to as a "cartilage tear" )
- ligament tear ( for the athlete who "blows out the knee" )
- kneecap problems ( including "chardroniolacia of the patella" and the "maltracking patella" )
- removal of loose bodies
- synonial disorders
- infection of the knee
Before we explain how arthroscopy is used to help knee problems, a little anatomy lesson is in order:The knee joint is the joining of three bones:
These are shown below in a schematic drawing:
- femur ( thigh bone )
- tibia ( shin bone )
- patella ( knee cap )
In between the femur and tibia are two shock absorbing cussions called menisci. There is a medial meniscus and there is a lateral meniscus. The medial meniscus is the shock absorber on the inside part of the joint ( labelled in the above schematic drawing and called "the medial side" by doctors ). The lateral meniscus is the shock absorber on the outside ( called the "lateral side" by doctors and also labelled in the abobe schematic drawing )
Shown below is a knee model where you can see the femur, tibia medial meniscus, and lateral meniscus.
Every time you walk, run, or jump the medial meniscus and the lateral meniscus absorb the full pressure exerted across the knee joint. It is easy to understand why they are commonly torn. They are extremely important structures because they protect the ends of the femur and tibial bones from damage. Without these cartilages, the ends of the femur and tibial bones would be unprotected and would grind on each other with every step you took. This would lead to a wearing away and deterioration of the ends of these bones. When this happens, you have arthritis. Arthritis is the painful and irreversible deterioration of the ends of the two bones.
Arthroscopy of Meniscal TearsWhen and arthroscope is inserted in a knee, both menisci can be seen along with surfaces of the femur, tibia, and patella. A typical view of a normal medial meniscus is shown below. Please also note the femur bone above the meniscus and the tibial bone below the menicus.
When the meniscus is torn, it looks like this:
Once the meniscal tear is found, it is trimmed so that the torn tissue is removed. This is usually done with a combination of instruments called biters and shavers. The trimmin instruments are inserted through a second small one quarter inch incision. These instruments are shown below:
The overwhelming majority of meniscal tears need to be trimmed and the torn portion removed. Only a very small percentage can actually be repaired. By repair, we mean putting stitches (called "sutures") across the tear so that it heals. Unfortunately, meniscal tears that can be repaired fall into a very a small category of tears classified by their shape and location putting sutures across a tear that does not meet the strict criteria does no heal the tear.
When athletes "blow out" their knee, they are referring to tearing of the anterior cruciote ligament (ACL). The ACL is the main stabilizing ligament of the knee and secures the tibia to the femur. The ACL is shown below:
The typical view of the ACL throught the arthroscope looks like this:
When the ACL tears, the knee becomes unstable and patients fell as if their knee will buckle or give way from underneath them. A young, active individual who has an ACL tear risks meniscal damage and arthritis withoout having surgery.
The surgical treatment of the torn ACL is "reconstruction" of the ligament. Surgeons cannot "repair" the torn ligament because it has a very poor blood supply. Putting stitches into the torn ends never works to heasl the ligament. Shown below is an arthroscopic view of a torn ACL.
Surgeons reconstruct the torn ligament with a donor tissue. Usually, the donor tissue (referred to as "the graft") is the middle third of the patella tendon ( the one below the pagella ), the hamstring tendon, or a cadaver ligament. Drill holes are made in the femur and tibia in the exact same location an direction as the old ACL. The donor tissue then becomes the new ACL and stabilizes the knee.