Knee Arthroscopy [Looking into the Knee with a key-hole camera]

Knee arthroscopy is the 'bread and butter' of knee surgery. It is not a single operation, but a technique by which a whole host of different therapeutic methods can be employed to treat the underlying condition.

Knee arthroscopy patients should therefore not 'compare notes' on the success or otherwise of their individual procedure as it is highly unlikely that any two people will be treated in exactly the same way for exactly the same underlying problem! In other words there is great variability in the perceived success of knee arthroscopy and this reflects the spectrum of disease being addressed.

The knee is relatively easy to arthroscope because the cavity is large and it is just below the skin on the front of the leg. Furthermore, most of the vital structures such as the large vessels and nerves are at the back, well out of harm's way. It is relatively easy to move around the knee and reach most of the important intra-articular structures. A tourniquet can be placed around the upper thigh, which means the surgeon can work in a bloodless field.

Generally, or as a rule of thumb, the younger the patient, the more likely the condition being treated is suitable for arthroscopic intervention. As one gets older, the more likely there are associated degenerative changes which limit the usefulness of the technique. But it is essential that your problem is put into context, which leads to the comments below.

X-rays and MRI scans are useful in terms of assessing knee problems, but there is no substitute for a careful history, clinical examination and experience in terms of deciding what would be best to do! It is easy to place too much reliance on these and other investigations.

A list of conditions commonly treated by knee arthroscopy would be too long to list here, but it is perhaps more useful to say that advanced, wide-spread wear i.e. advanced osteoarthritis, responds poorly if at all, and should rather be treated by knee replacement.

Meniscal [Cartilage] Tears:

There is a problem with medical and lay terms for the 'cartilage' of the knee. To the medical mind, the word cartilage usually refers to the glistening, shiny-white coating on the end of articulating bones in a synovial joint. This is termed hyaline cartilage. To the layman, the words 'I have a torn cartilage in my knee' refer not to damage to the hyaline cartilage, but a separate structure called the meniscus (plural menisci).

Probably the most common abnormality treated by knee arthroscopy is a meniscal tear. The menisci are 2 semi-circular or crescent shaped structures within the knee made of fibro-cartilage (as opposed to hyaline cartilage), similar in composition to the 'cartilage' of your ear-lobe. They are sandwiched between the femur and the tibia in the middle of the knee.

In normality, they are soft and springy to absorb axial shocks on the knee, share the mechanical load with the bone, assist with lubrication by acting as 'wind-screen wipers' and help to make the knee stable.

A plastic model of the right knee, seen from the front. The arrow indicates the medial meniscus.

Menisci of a right knee as seen from above, lying on the top of the tibia. The purple shaded area towards the back of the medial meniscus corresponds with the area most frequently torn.

With time, the menisci (you have 4 of them, 2 on the left and 2 on the right), may become stiff or the knee articulating surfaces may become roughened, leading to abrasion. In these circumstances, a relatively minor event, such as missing a step or twisting the knee, may lead to a tear in a a meniscus. The tear produces local inflammation and pain, perhaps with a click or sense of something moving around inside the joint. The joint may fill with extra fluid, leading to noticeable swelling and stiffness. [Often colloquially called 'water on the knee'].

Meniscal tears are usually dealt with by resecting the torn piece through the arthroscope. A very small minority of tears, mainly in younger patients, can be repaired. The vast majority occur in older patients who already have some evidence of early degenerative change, and in these circumstances the piece of meniscus excised will not be missed! A full discussion of meniscal excision versus repair is outside the scope of this website. In any case, it is a decision that can only be made on an individual basis, and when the surgeon has seen the damage at arthroscopy.

Knee Arthritis

When the hyaline cartilage covering the ends of the bones in a synovial joint degenerates, this is termed arthritis. There are many causes, but sometimes we do not know what started the process, in which case it is termed 'Primary osteoarthritis'. An example of a well-known underlying cause of joint degeneration is rheumatoid arthritis.

Whatever the cause, the hyaline cartilage progressively becomes dull or soft and begins to break up. This makes the articulating surfaces rough and triggers a series of reactions in the joint and surrounding tissues. The joint may swell, grate or catch and the patient will eventually experience disabling pain.

In the advanced phase, knee arthritis is best treated by knee replacement (vide infra).

Advances are taking place all the time in terms of repairing, transplanting or regenerating hyaline cartilage in the knee, but the indications for such techniques are currently very narrow and some of the available techniques are less than reliable in practice. The most suitable candidates are usually young, high demand athletes with a small, isolated lesion.

See the section on Knee Replacement for more information.