Knee arthroscopy is surgery done using key-hole (1cm long) incisions and a telescope (“arthroscope”) inserted into the knee joint. A number of different knee conditions can be treated using arthroscopic surgery. This includes:

• Removal or repair of a damaged meniscus
  
• Removal of loose bodies within the knee joint
  
• Removal of loose, unstable, painful flaps of degenerative/arthritic cartilage
  
• As part of reconstructive surgery to treat a torn anterior or posterior cruciate ligament
  
• As part of a procedure that can be used to stabilise dislocating patellae
  
• Removal of inflamed synovium from inside the knee capsule in cases of inflammatory arthritis that have recurrent painful swellings, where there isn’t advanced degeneration of the articular cartilage
  
• Occasionally as a means of diagnosing and treating infection within the natural knee joint.

Arthroscopic surgery is frequently done under a general anaesthetic (although a spinal anaesthetic can be used in some occasions/patients instead). Once the patient is anaesthetised and the leg has been painted with antiseptic, two or three small incisions can be made at the front of the knee, just below the patella, on either side of the patella tendon. Next a 4mm diameter arthroscope is introduced into the knee to survey the various cartilage surfaces of the femur, patella and tibia, as well as the menisci and the anterior and posterior cruciate ligaments. The integrity of these structures can be seen and they can be tested to see if they’ve been damaged with the use of a small probe, a little bigger than a crochet hook. The medial and lateral collateral ligaments cannot usually be seen directly as they lie outside the knee joint itself. If any damaged material is seen within the knee, then small manual tools, sutures or even miniature motorised shavers, burrs and heat probes can be introduced into the knee to remove or repair the damaged tissues.

The operative time of an arthroscopy can vary enormously, depending on what needs to be done within the knee, but can be as short as 15 minutes and as long as many hours for complex multi-ligament reconstructive surgery. The majority of procedures tend to be in the shorter operative time-scale (i.e. under an hour) and usually require only a day-stay in hospital, being discharged home to a responsible adult later on the same day. You will usually be able to walk on the same day with the use of crutches.

The benefits of arthroscopic knee surgery, in general, is less trauma to the tissues surrounding the knee and so there is usually a shorter rehabilitation. Despite these small skin incisions, fairly involved and extensive surgery can be performed inside the knee and so there may be more discomfort or swelling than might be otherwise expected, with relatively little outward sign of what has been done inside the knee joint. The main drawback of arthroscopic surgery is that it is impossible to perform certain procedures such as total or partial knee replacement through such small incisions. It is also difficult to reach certain locations such as the back of the knee joint, and vision can be obscured if there is bleeding into the knee joint during the surgery.

A torn meniscus is a fairly common condition seen, usually as a consequence of pivoting suddenly or forcibly on a flexed knee or during a deep squatting motion. The femur and tibia may snag part of the meniscus and crush, grind or tear it between them, causing fairly sharp and localised pain to either side of the knee, gradual swelling over a few hours or a day, and occasionally a painful clunking sensation during walking, running or pivoting on the knee. Rarely if the torn piece of meniscus gets jammed between the tibia and femur again it may cause the knee to lock in a bent position for a few minutes until the muscles relax, or it may cause the knee to give way or collapse with pain due to reflex muscle spasm. Depending on the age of the patient, the age of the injury, and the pattern and location of the tear within the meniscus it may be feasible to attempt to repair a torn meniscus arthroscopically, however, if these features are unfavourable for a meniscal repair, then the damaged portions of the meniscus may be removed instead, similar to how an infected appendix can be removed. In theory, a knee with a removed meniscus may be at higher risk than a normal knee of developing later osteoarthritis as the force distribution within the knee has been disturbed. However, the alternative of leaving a damaged meniscus within the knee in the hope that it will protect against developing arthritis usually means a lifetime of intermittent pain and loss of function, which most patients (rightly) won’t tolerate.

In a similar fashion, knees with very mild arthritis but which suffer from mechanical symptoms such as painful locking, painful clicking or giving way, may have some limited benefit from arthroscopic surgery to remove debris from within the knee that may get jammed between the tibia and femur such as unstable arthritic flaps of cartilage or loose bodies that float around within the knee. The recovery from the mechanical symptoms could be expected to be similar to removing a torn meniscus, however, there is a chance that the arthritic symptoms of aching and swelling may deteriorate despite having removed the local mechanical problem.