Introduction

Cartilage (or chondral) ulcers are extremely common causes of pain in the knee. I often see these problems in patients who are physically active and participate in sports that involve a lot of lower limb movements like running and jumping.

If not treated, these problems will often deteriorate with time, resulting in increased pain and even arthritis later on in life. In order to understand the problem better, some basic knowledge of the anatomy of the knee joint is necessary.

Anatomy of the Knee Joint

The knee joint is a hinged joint, made up of 3 bones: the femur (thigh bone), the tibia (shin bone) and the patella (kneecap).

As the knee joint is a hinged joint, the main movement that occurs at the knee is in one plane – bending and straightening. However, a little bit of rotation does occur when the knee is fully straightened.

The surfaces of the knee joint are covered with a smooth cartilage. The cartilage not only ensures frictionless movements during knee flexion and extension, but also absorbs shock when impact from activities like running or jumping are experienced.

Cartilage is largely composed of cartilage cells scattered within a matrix composed of proteins, collagen and water. It is interesting to note that cartilage does not contain blood vessels or nerves. Cartilage cells, thus, derive their nutrients via diffusion from joint fluid.

How does a cartilage ulcer occur?

Cartilage ulcers can occur in isolation, or in combination with other structures within the knee joint like the menisci and ligaments. I often see these problems in physically active people who regularly engage in sports that place a fair amount of stress on their knees, such as running, racquet sports etc.

While they are most commonly encountered in the knees, the same problem can occur anywhere cartilage exists. The shoulder, ankle and elbow are other commonly affected joints.

While the exact mechanism of injury is not well understood, and is likely to be multifactorial. Vigorous physical activity alone cannot adequately explain the occurrence of cartilage injuries.

What symptoms may I have?

Most patients experience in the knee during movements. The exact site of the pain and movements that bring it on will vary depending on the site of the cartilage injury.

If the cartilage injury is located on the cartilage of the kneecap (patella), the patient will experience pain at the front of the knee, aggravated by movements such as standing from sitting position, going down stairs and slopes, jumping etc.

If the cartilage injury is located on the femoral condyle, the patient may have pain when standing, walking or bending the knee at certain angles.

Many patients will also notice swelling of the knee occurring a few hours after sports. The swelling will often last for a few days then resolve if they rest. It tends to recur every time they do sports.

What tests can be done to confirm the diagnosis?

An MRI scan is highly accurate for diagnosing cartilage problems. The MRI will be able to provide details about the cartilage injury which your doctor will need to decide on the most prudent form of treatment for you.

Characteristics of the cartilage problem such as site, size, depth, underlying bone issues, associated meniscus injuries, ligament tears etc will be clearly seen on the MRI. For a more detailed discussion regarding MRIs, please go to the page on investigations.

I am told I have cartilage ulcer. Can it heal by itself?

Most cartilage ulcers cannot heal by themselves. This is because cartilage is avascular, meaning there are no blood vessels within cartilage. An adequate blood supply is vital for healing because blood carries nutrients necessary for cells to bring about healing. As cartilage only receives nutrients via diffusion from joint fluid, the limited amount of nutrients it can receive this way retards its ability to heal.

Having said that, some cartilage ulcers do eventually become covered with “scar cartilage”. Again, it is not clear why some scar up and some do not. The scar cartilage, however, is not the same type of cartilage as the original articular cartilage. It is a type of cartilage known as fibrocartilage. Fibrocartilage has inferior properties compared to articular cartilage.

What will happen if I leave it alone then?

The cartilage ulcer is likely to either remain the way it is, or progressively get worse over years. The deterioration of the condition does not occur immediately or quickly. For some patients, the acute pain abates when inflammation and bruising of the underlying bone resolves and if they are not particularly active, the knee may not bother them again for years.

For some patients, however, the site and extent of injury to the cartilage affects even their daily lives or lifestyles. For such patients, leaving the ulcer alone may not be a very attractive option.

What treatment options are there?

Unfortunately, non-invasive techniques may in some patients, reduce the symptoms caused by cartilage ulcers, but will not be able to effect healing of the ulcer. Having said that, I generally prefer to start patients off on non-invasive treatment options first before moving on to more invasive treatment modalities.

What non-invasive treatment options are there?

Non-invasive treatment options include anti-inflammatory/ pain medications and physiotherapy.

Anti-inflammatory medications work by reducing inflammation in the joint. They are very effective in reducing pain, but do not “treat” the cartilage ulcer per-se. I often prescribe them for acute pain but if the pain is persistent and severe enough to require frequent medications, more directed treatment modalities are likely required.

For patients who have cartilage injuries involving the cartilage covering either the kneecap or the trochlear (part of the femur on which the kneecap glides during knee flexion and extension), physiotherapy may be of benefit. In theory, it works by improving the muscle balance between the knee flexors and extensors, and may in doing so, reduce the amount of pressure exerted between the 2 bones.

Are there any injections that can treat cartilage ulcers?

Injections
Several types of injections are commonly used in the treatment of cartilage ulcers.

Steroids
Steroids are highly effective in reducing the amount of pain that a patient with a cartilage ulcer might experience. Unfortunately, the pain reduction is often temporary. They work by suppressing inflammation. Since inflammation is the natural process that results in the sensation of pain in the body, by suppressing inflammation, pain is also reduced.

Steroids, however, will not help to induce healing of the cartilage ulcer. The converse is true, actually. Studies have found that some steroids are toxic to cartilage cells in laboratory studies. A singe injection of steroids is not likely cause any significant cartilage toxicity, but repeated injections should be avoided.

Platelet-rich plasma (PRP)
PRP is increasingly used in the treatment of various medical conditions, including cartilage ulcers and arthritis. Conceptually they are great. They involve drawing a small amount of blood from you, spinning it down in a centrifuge and extracting the part that contains high concentrations of naturally produced substances in the body that have the ability to suppress inflammation and stimulate healing.

Unfortunately, result of PRP in the real world has not been stellar. There have been conflicting reports with regards to its efficacy. In addition, the Ministry of Health, Singapore had, in 2013, released guidelines for the use of PRP and its intra-articular use is not approved.

Autologous protein solution (APS)
APS is a relatively new product developed for use in joints. It is similar to PRP in the sense that both are derived from the patient’s own blood and make use of proteins and substances naturally present in the blood to promote tissue healing.

However they are different in that APS contains white blood cells and anti-inflammatory cytokines which are not present in PSP. Clinical data with regards to its efficacy is also not clear at the moment.

Viscosupplementation
Various preparations that contain hyaluronic acid are in the market and commonly used. They are not designed for the treatment of cartilage ulcers, but are not uncommonly used for this purpose. As such, their efficacy in the treatment of cartilage ulcers is not well studied and is not something I advocate for this condition.

All the treatments so far are temporary. Are there any permanent solutions?

Yes, certainly! There are various surgical procedures that are commonly used in the treatment of chondral ulcers. The decision regarding which procedure to use depends very much on the size of the ulcer and the familiarity of the surgeon with the various procedures. Unfortunately, no one procedure has been conclusively proven to be foolproof.

What procedures can treat my chondral ulcer?

Articular cartilage is difficult to replace. Most procedures, if successful, result in healing and coverage of the chondral ulcer with fibrocartilage (scar cartilage). Fibrocartilage has inferior load bearing and wear properties compared to articular cartilage, but it is better than having no cartilage at all!

Small chondral ulcers which are not full thickness (not extending down to the bone) and have flaps on its edges may only require the flaps to be trimmed. The aim of such procedures is simply to prevent the edges of the flaps from being caught in the knee during knee movements, hence causing pain.

Chondral ulcers that extend down to the bone will usually require more than just a trim. The aim in such chondral ulcers will be cartilage repair. Meaning, the aim is to get the chondral ulcer to heal over so that the underlying bone is again, covered by cartilage. Cartilage repair is still an evolving field, so while the techniques described below are guides and standard practices of some doctors, not everyone will agree.

Although some guidelines suggest that different sized chondral ulcers should be treated using different techniques, the evidence that one treatment modality is better than the other is rather poor. The more commonly used techniques are:

1. Microfracture

This is arguably the most commonly performed procedure aimed at cartilage repair. This is an arthroscopic surgery (keyhole surgery) which involves making small holes in the exposed bone in the base of a chondral ulcer. Each hole measures about 1 mm in diameter and 4-5 mm in depth.

The theory of how microfracture works is that it allows stem cells to escape from the bone marrow in the bone, while also establishing some blood supply from the underlying bone (since as mentioned above, articular cartilage does not have a blood supply, hence is unable to heal by itself).

Because stem cells have the ability to transform themselves into different types of cells upon maturity, the hope is that the stem cells will transform into cartilage cells and will then produce cartilage to eventually cover the ulcer.

2. Autologous Matrix-induced Chondrogenesis (AMIC)

This is a rather big term, but it is simply the application of either a hyaluronic acid or collagen patch (matrix) over the chondral ulcer after microfracture has been performed. The theory is that there is a worry that the stem cells in the bone marrow that has been liberated from the bone may not stay within the ulcer, but may be washed away by the joint fluid.

The patch traps the stem cells in place while they transform into cartilage cells. After a few weeks, the patch will dissolve and no foreign material will be left in the joint. By then, the newly created cartilage cells would have anchored themselves in the ulcer and will no longer be at risk of being washed away.

3. Osteochondral Autograft Transfer (OAT)

This procedure is more often performed for slightly larger chondral ulcers. A cylindrical plug of healthy cartilage together with the attached underlying bone is harvested from elsewhere in the knee that is not loaded during weight bearing.

A similar sized cylinder of bone at the base of the chondral ulcer is then removed and filled with the harvested cartilage-bone cylinder, thus resulting in coverage of the chondral ulcer.

4. Autologous Chondrocyte Implantation (ACI)

This is an interesting technique that has, over the years, undergone several changes aimed at improving its efficacy. It involves a 2-surgery process. The first surgery involves an arthroscopy where heathy cartilage is harvested from parts of the knee that are not involved in load bearing.

The cartilage cells are then grown in a laboratory. When sufficient numbers of cartilage cells have been grown, they are then transferred onto a collagen membrane. The second surgery then involves transferring the cell-infused membrane into the chondral ulcer.

Over the course of months, the cartilage cells then detach from the membrane, become established in the chondral ulcer, then start to grow new cartilage to cover the ulcer.

The need for 2 surgeries, however, make this unattractive to many patients. As such, newer techniques requiring only a single surgery are being performed. In Singapore, harvesting stem cells from other sources, such as bone marrow, trapping it in a 3-dimensional matrix composed of a derivative of hyaluronic acid, and placing the bone marrow-soaked matrix in the ulcer is now being performed by some doctors.

It is then hoped that the stem cells within the bone marrow will then transform into cartilage cells and eventually fill the chondral ulcer with new cartilage.

Some doctors use size of the chondral ulcer to decide what technique to use. While the newer techniques of using bone marrow as a source of stem cells has potential, studies have not yet conclusively proven the superiority of one technique over the other.

What kind of anaesthesia will I require?

I often do these surgeries under general anaesthesia. An anaesthetist will be present throughout the surgery to not only anaesthetize the patient, but also to monitor the patient throughout the duration of the surgery to ensure safety of the patient. Please read the section on anaesthesia for more information.

How long does the surgery take?

The surgery usually takes an hour, but complicated cases can take longer.

Is this surgery very dangerous?

Not at all! Risks of any procedure can usually be divided into anaesthetic risks and surgical risks. For most patients, the risk of any serious adverse event happening is less than 1-2%. However, as every patient is different, it is important that you have a detailed chat with your doctor with regard to your risk.

Can I return home on the same day as the surgery?

Yes, certainly you can return home on the same day. Many patients, however, find it more convenient to stay overnight. This is because you may be feeling rather drowsy and tired after you wake up from the anaesthesia.

Will I be able to return to my sport?

Yes absolutely. Many patients are able to return to their sport at a similar level to what they were doing pre-injury.

How long will I take to recover?

Full recovery usually takes 4 – 6 months. Physiotherapy is fairly important after the surgery. Most doctors will restrict the amount of body weight the patient is allowed to put on the operated leg for a period of about 6 weeks.

Weight bearing is then gradually increased. Physiotherapy performed in a graduated fashion will help get patients to safely and progressively weight bear, walk unaided, jog, jump, run and finally get back to their sport of choice. For more details about physiotherapy, please refer to the section on Physiotherapy.

What should I do now?

If you have managed to get to this part of this long article, your shoulder must be bothering you significantly! Consult your family doctor or see an orthopaedic specialist and he/she should be able to advise you accordingly.