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- Fibrous cartilage: (meniscus), which has tensile strength and can resist pressure.
- Hyaline cartilage: Which covers the surface along which the joints move.
Cartilage will wear over the years, as it has a very limited capacity for self-restoration. The newly formed [healed Scar] tissue will generally consist for a large part of fibrous cartilage of lesser quality than the original hyaline cartilage. As a result, new cracks and tears will form in the cartilage over time.
What is a meniscus?
- The menisci (plural of meniscus) are horizontal horse shoe shaped wedges of tissue that exist both on the inside and outside aspects of the knee acting as shock absorbers between the long bones making up the knee.
- Each knee has 2 menisci, one to support each of the rounded ends (condyle) of the femur (thigh bone).
- They are made of smooth white glistening fibrous material, and have a vital function in reducing dissipating shock forces acting on the knee during day to day activity.
- They are wedge shaped and curved, with the wider part of the wedge forming the outer rim and the inner rim being the sharp surface.
- The majority of the meniscus does not have a blood supply and it is for this reason that healing of these tissues once damaged is very unlikely.
- These two disks, the medial meniscus and the lateral meniscus, consist of connective tissue with extensive collagen fibers containing cartilage-like cells. Strong fibers run along the menisci from one attachment to the other, while weaker radial fibers are interlaced with the former.
- The menisci serve to protect the ends of the bones from rubbing on each other and to effectively deepen the tibial sockets into which the femur attaches.
- They also play a role in shock absorption, and may be cracked, or torn, when the knee is forcefully rotated and/or bent.
- Consequently, people who have damaged their cartilages often ultimately require surgery to excise the torn fragments.
The Articular Cartilage, also known as the joint lining,( Hyaline cartilage) is a protective layer of tissue located on the ends of the bones which come together in the knee joint. These bones are the femur (thigh bone), tibia (shin bone), and patella (kneecap).
Articular cartilage can be damaged through an injury or gradually deteriorate over time from a variety of factors. When the articular cartilage is damaged or injured, it usually goes through a staged process of softening, flaking, fragmenting, and finally complete loss where the underlying subchondral bone is exposed. This process is commonly known as osteoarthritis.
Damaged or injured articular cartilage has a very limited ability to heal itself. Therefore, once the process of osteoarthritis starts, there is little that the body can do to stop the deterioration.
Articular Cartilage surgery:
There are several procedures that can be done for damaged articular cartilage. The decision of which procedure to perform is based on the extent of damage seen during arthroscopy and on MRI scans and x-rays. Important indications include the size of the damaged area - both in diameter and depth.
Small articular cartilage lesions (less than 1 cm2 in diameter and extending only partially down into the cartilage; not to the subchondral bone which lies beneath the articular cartilage) are usually treated arthroscopically by debridement and drilling, abrasion, or microfracture.
The drilling/abrasion/microfracture procedures all work off of the concept that producing very small holes in the subchondral bone will stimulate a healing response that forms tissue resembling articular cartilage (called fibrocartilage).
What are the symptoms of a damaged meniscus?
- Damage to the menisci or cartilage can occur at any age. Whilst one classically associates this injury with a young footballer sustaining a dramatic injury, in our experience it is seen just as commonly in a slightly older population who can be doing no more than simply going for an unusually long walk at a weekend.
- In short, the damage to the meniscus is an extremely common condition that can occur during practically any form of activity.
- It is not unusual for patients to present with symptoms or signs of a torn meniscus without being aware of any specific episode to which they can attribute the damage to the cartilage.
- Injury to the meniscus is associated with the classical symptom of pain felt along the inside or outside aspect of the knee depending on which cartilage has been torn.
- Often this pain is slightly intermittent in nature and may appear to get "better" only to come back and trouble the patient at a later stage.
- The pain is often associated with a swelling which comes on gradually after the tear but in some cases does not occur at all.
- This twinging discomfort that patients often feel is often exacerbated by any twisting activity of the knee and may occasionally be associated with more classical symptoms of a sense of giving way within the knee and very occasionally of locking (inability to fully straighten the leg).
- All these symptoms are obviously troublesome to patients and often prevent them from returning to any sporting activity.
- As a result of this, often a specialist opinion is sought and further investigations can be undertaken to confirm the diagnosis.
Diagnosis of meniscus tear:
- Whilst plain x-rays (radiographs) of the knee are not particularly helpful in showing evidence of damage to soft tissue such as the cartilage within the knee, they can be useful in excluding the presence of a significant degenerative disease such as osteoarthritis.
- Once you have seen the specialist it is likely that the knee will be examined particularly looking for signs of inflammation such as an effusion (swelling within the knee) or tenderness around the joint line surface.
- Whilst signs on examination point towards the possibility of a torn cartilage, the best way of confirming this if surgery is to be considered is to undertake a Magnetic Resonance Imaging [MRI Scan].
- This investigation [MRI Scan] involves placing the knee in a magnetic loop coil which produces very high resolution pictures detailing the condition of the soft tissues associated with the knee.
- These scans are accurate (95%) enough to show whether a meniscus is torn and thus a decision can be taken about the need for surgery.
- There is never an absolute need for surgery just because the cartilage is torn, however if the symptoms are annoying enough the patients often elect to press on with surgery.
Medial meniscus tear [MRI Scan]
Meniscus surgery & Arthroscopy:
If the meniscus has multiple tears located in different regions, is shredded or severely deteriorated due to multiple injuries, then it cannot be repaired. It may be possible to save some of the meniscus, but if it must be removed it can be later replaced with a transplant.
Meniscectomy (or partial meniscectomy) refers to removal of all or part of a damaged cartilage within the knee called the meniscus.
This is probably one of the most common procedures now performed by knee surgeons in the UK and is performed using a technique referred to as arthroscopy.
- The arthroscopy involves inserting a small telescope attached to a camera into a small incision at the front of the knee (portal). This allows the whole of the knee to be inspected with water being used to inflate the knee.
- A fibre optic telescope instrument is used to view the internal cavity of the knee.
- The surgeon makes another incision through the other side of the front of the knee to insert small instruments to cut away the loose or torn fragment of the damaged meniscus. Whenever possible the surgeon will remove only the damaged portion of the cartilage leaving as much of the cushion function of the cartilage intact.
- This procedure takes place with the patient under either a general or regional anaesthetic.
- This allows the knee to be fully examined and the suspected damage to the cartilage (meniscus) to be confirmed and treated at the same time.
- The tear in the cartilage is often found at the back portion of the knee and access to this area can be difficult which is why the experience of the surgeon is critical.
- At the end of the procedure, which often lasts approximately half an hour, the 2 small puncture mark incisions are closed either with a small stitch or a paper strip.
- The patient remains in hospital for an average 4 hours after the surgery.
- The surgeon will see the patient before they are discharged, hopefully having explained what was found at the time of surgery.