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Meniscal injuries

Identifying the type of meniscal injury is the key to deciding the right treatment

It would be a mistake to think that all cartilage tears are the same. Not only do cartilage tears vary, depending on whether they are on the inner (medial) or outer (lateral) side of the knee but also in the area of the cartilage that is torn as well as the configuration of the tear itself.

For example, tears towards the peripheral aspect of the meniscus may have a greater chance of healing as these are known as 'red/red' tears with a significantly better blood supply than the ones towards the inner aspect of the knee (white/white). The tears with poor blood supply, which represent the majority of injuries, unfortunately, have no capacity to heal as the blood supply does not bring in the appropriate materials to allow the repair to occur.

Equally, if the tear is a sideways split within the cartilage – known as a horizontal cleavage tear – these also tend to heal badly and are found in “older” patients, often with previous degeneration within the substance of the meniscus itself.

Perhaps the most common tear we see is an oblique under-surface tear that creates instability in the cartilage, thus creating traction on the very sensitive capsule attached, producing the sharp stabbing pain felt by the patient.

These tears, together with flap-type tears, can often cause significant sharp discomfort as well as occasional locking, as discussed earlier under the heading of symptoms. It is important to distinguish between the different types of tear, particularly if one thinks the whole of the cartilage has become displaced and flipped into the middle of the knee, which is referred to as a bucket-handle tear. In some instances, when the knee itself is locked, there is then a degree of urgency to proceeding to unlock the knee via surgery. This allows for potential repair to be undertaken.

Meniscal surgery

If the decision has been taken to proceed to surgery, as a result of persistent symptoms or a more acute need to unlock a knee, then the procedure to deal with the cartilage is usually referred to as a partial meniscectomy. This is a relatively straightforward keyhole operation carried out under general anaesthetic, lasting approximately 20-30 minutes. 

The operation involves the insertion of a camera or arthroscope with miniature instruments into the knee through two small 4mm incisions in the front of the knee. The damaged part of the cartilage is trimmed and the residual rim of the cartilage is shaped to resemble the initial smooth surface. As little of the cartilage, usually approximately 20-25%, is removed as possible in order to preserve the function of the remaining healthy portion.

Once the whole of the inside joint cavity has been thoroughly inspected and any other defect or damage is noted, the instruments are removed and the incisions closed.

In a minority of patients, particularly the younger patients, the tear is within the healing red/red zone, discussed above, which has a good blood supply. These tears may be suitable for repair with internal stitches, rather than excision.

Obviously, where possible, any attempt to preserve the cartilage and its function is beneficial, particularly for the younger age group.

It is important to remember that the meniscus has a very important function and without the appropriate volume of meniscal tissue, the possibility of increased stresses occurring across the joint, leading to degenerative change in later life, is well established. It is for this reason that every attempt to try and be conservative during surgery is made.

Your surgeon will carefully go through the risks, benefits and alternatives for each procedure prior to any planned surgery.

In older patients, we know that the articular cartilage lining the joint may already be significantly diminished (osteoarthritis). In an osteoarthritic knee, the MRI scan may reveal a crushed and complexly torn meniscus. This is often referred to as a degenerate meniscal tear. Keyhole surgery to treat a degenerate meniscal tear may not only fail to treat the symptoms but may instead aggravate the knee further. A rare complication from arthroscopic surgery, possibly caused by the pressurised water, is spontaneous osteonecrosis (SONK). This tends to happen more commonly in patients over the age of 50 and is normally usually a self-limiting condition that settles over a period of months without any further treatment. 

It is usual for you to be able to walk without sticks or crutches immediately after the surgery but we advise limiting walking to short distances for the first few days and outpatient physiotherapy soon after the surgery is also recommended.

It is important to build up gradually to normal activity levels, especially any sporting activity.

Driving is normally possible after two days, once you are confident enough to be able to do an emergency stop.