Knee

A joint is the movable link between the ends of two rigid bones. To prevent rough and possibly jagged bones rubbing against each other, the contact areas are coated with a slip membrane, a 3-4 cm thick cartilaginous tissue. This extremely smooth cartilage reduces friction within the joint and cushions hard impacts, e.g. when running.

Structure of the multi-layer cartilaginous tissue

Traumatogenic cartilage damage in younger patients

Generally as the result of an accident (skiing, playing football or similar), a piece of cartilage of about 1-2 cm diameter in size can break off the otherwise complete cartilage. The surrounding edges are intact and of normal height, the underlying bone healthy and of good regenerative capacity. This type of injury responds well to the treatment options mentioned below.

Degenerative wear

Less favourable is the outlook for cartilage damage developed in the course of a life-time by years of monotonous stress alone or in conjunction with bow-leg or knock-knee deformities, gout or rheumatism, damage to the menisci or the cruciate ligament; initially, this results in softening of the cartilage (stage 1), followed by fissuring of the softened cartilage (stage 2). In stages 2-3, the cartilage layer is only half as thick as normal and extremely frayed; there may be detached or loose fragments of cartilage.

Stage 3 degeneration with thinning of cartilaginous tissue

Terminal stage 4 with complete destruction of cartilage

This stage can no longer be repaired by the body itself without outside intervention. These cases are classified as severe cartilage damage, even though pain levels may still be bearable and thus not perceived as warning signals by patients. It is at the early stage of progressive cartilage degeneration, though, that modern cartilage surgery has the greatest prospect of success.

At terminal stage 4, the cartilaginous tissue is completely destroyed, the "tyre profile" worn away. Bone grinds on bone, grooves develop and bony overgrowths make it increasingly difficult to straighten the leg; knock-knee or bow-leg malalignments may worsen. At this stage, even modern surgical interventions to restore the cartilaginous layer still only promise limited success. The basic principle is: once cartilage damage has begun, it is going to progress at increasing speed; without early therapeutic intervention, freedom from pain can only be achieved by implanting an artificial joint prosthesis.

Treatment of arthrosis

This depends on the cause and severity of the disease. Arthroscopy does not just permit us to see the damage to the cartilage and to record it on video for later documentation, but also gently to treat it at the same time, using micro-instruments.

Debridement

A miniature bur/cutter is used to remove the frayed edges and smooth the surface. Unstable cartilage parts have to be removed to prevent further fraying and shredding. At the same time, damage to the menisci is repaired; at the early stage, suturing the meniscus is the preferred solution. In some cases, it also makes sense to remove parts of the synovial membrane (synovectomy).

Various methods of cartilage regeneration (stem cell techniques)

These are based on the migration of bone marrow stem cells into the area of cartilage damage, which at that site develop into replacement cartilage.

For this reason, in cases of half-thickness cartilage defects associated with severe fraying, an attempt can be made to stimulate the body's own cartilage repair. For the initial 3-4 years, this replacement cartilage is comparatively cell-rich and does not contain as many chondrocytes that produce synovial fluid. For this reason, it does not withstand mechanical stress as well as the original cartilage (hyaline cartilage) and often gives rise to irritable knee symptoms. However, this replacement cartilage (fibrocartilage) is still better than a completely exposed bony surface.

Microfracture technique as developed by Dr Steadman involving freshening of the bone from which replacement cartilage can develop.

Microfracture technique (as developed by Dr Steadman)

The beginnings of surgical freshening of cartilage date back to the 1950s (Pridie drilling). This involves the drilling of several 2 mm wide holes into the open surface of the bone to give it the appearance of a sieve. This creates "islands of regeneration", but only in very few cases continuous fibrocartilaginous scar tissue. These days, we prefer the less traumatic "microfracture technique" as developed by Richard Steadman in the early 1990s. A fine awl is used to pierce the surface of the bone to create hairline cracks and tiny holes, resulting in the formation of firmer fibrocartilaginous scar tissue that covers the entire affected area.

Picture this in your mind like sowing grass seeds on soil that is firmly trodden down and dried: without loosening the soil before sowing, the seeds would have no chance of taking root. Piercing the surface of the bone has the same effect: it loosens the bony surface and allows the seeping out of bone marrow stem cells or of blood stem cells. After sowing, the seeded area must not be walked on for several weeks, otherwise the seeds are trampled on straightaway. The same applies to the joint: walking aids must be used for a period to prevent weight being placed on the operated knee.

Arthroscopic microfracture
treatment of extensive cartilage damage in the knee joint.

Abrasion arthroplasty (developed by Dr L L Johnson)

If parts of the bone are already exposed (stage 4), the options are either to debride the bone and smooth the remaining cartilage and await the degree of improvement, or to help the body to recover the bald areas of bone with fibrocartilaginous scar tissue. The results can be just as good as those after microfracture. In this procedure, we freshen the exposed, extremely hardened surface of the bone with small cutters, as introduced by Dr L Johnson in the early 1980s.

Cartilage paste drafting (as developed by Dr K R Stone)

A homogeneous paste of bone marrow and cartilage pieces is pressed into the area of the cartilage defect that was earlier freshened with microfracture. Dr Stone reports a significant improvement in the formation of regenerated cartilage and faster transformation into a tissue similar to hyaline cartilage than achieved by previous stem cell techniques. This method sounds very promising, as it combines a greater chance of recovery with an acceptable cost. However, the technique is still comparatively new and has not been tested over long periods of time.

Various methods of cartilage transplantation

Cartilage-bone transplantation (osteochondral autologous transplantation (OATS) and mosaicplasty)

Small round "plugs" of bone and cartilage are removed from less affected areas in the patient's own knee and inserted into prepared holes in the defective area. The advantage: immediately operational hyaline cartilage in the defective area and good healing and integration, as the underlying block of bone ensures fast osseointegration. Costs are kept within reasonable limits. However, the method is technically quite challenging, particularly if executed arthroscopically, and requires a high degree of surgical expertise and experience.

Cartilage cell cultivation and transplantation

This technique has caused a stir in the media since its introduction in the mid-1990s. In a first step, some cartilage particles are surgically removed from the knee joint, then in a complex process propagated in a cell culture and finally implanted in the defective area in a second surgical procedure. There the new cells have to implant and propagate further to generate a new cartilaginous structure - a very complex process requiring strictest compliance with follow-up care guidelines.

However, the procedure is very costly indeed; the propagation of the cells alone costs from CHF 8,000 to 12,000; this cost is at present generally not funded by health insurers. Furthermore, the surgical technique is very challenging and currently still requires a second open surgical procedure.

The purpose of all of these procedures is to restore the affected or worn cartilage covering of the joint. However, this can only be successful if all underlying disruptive factors have been eliminated:

• all meniscal lesions have to be smoothed or - better still - sutured back into place. At present, meniscus transplants are not yet available for wider clinical use, but in this area, too, we are working on further advances.
• All ligament instabilities have to be eliminated; the anterior (front) cruciate ligament in particular has be sufficiently stable.

Large cartilage defect (osteochondrosis dissecans) in the knee joint		Typical cartilage-bone plugs to insert into the defective area
		Special instruments (diamond cutters)

 

What other surgical procedures can be performed in order to avoid a knee prosthesis?

• Transpositional osteotomy
  The leg axis has to be straight. In a bow-leg malalignment, the corrective procedure is generally carried out at the head of the tibia, in a knock-knee malalignment at the lower end of the femur. In both procedures, the respective bone is carefully cut and precisely rejoined in the desired alignment; it is then held in place with metal clamps or screws, until this artificially "broken bone" has healed. Such realignments can be combined in a single session with freshening or transplanting cartilage.
  Another option consits of "open wedge" realignments on the inside of the knee for further tightening of the medial collateral ligament.
  Although this may sound like major surgery; the realignments generally heal faster than the freshening of the destroyed cartilage in the knee joint to stimulate the growth of a new layer of cartilage, known as a "bioprosthesis"
• Aftercare following joint-preserving arthrosis treatment
  Depending on the severity and extent of the arthrosis, weight has to be kept of the knees for up to 10 weeks with the use of forearm crutches. For the first 6-8 weeks, only the "heel-to-toe" movement of the foot is permitted with a load of no more than 5 kg. The remaining 2 weeks are used to reintroduce and get used to full weight-bearing. For this whole period, though, you should move your joint as much as possible. We frequently prescribe the use of a motorized continuous passive motion (CPM) device. The more hours you use this appliance (at least 4 hours per day in addition to 3-4 hours at night), the better the expected results.
  Regarding the concept of treatment with a continuous passive motion device, as early as 1984 the Canadian doctor R. Salter was able to show excellent results in animal experiments following 6 weeks of continuous treatment even in cases of severe joint damage. However, it is not feasible for human patients to be tied to a motion device for six whole weeks, and many disorders in animals heal much faster and better than in humans. Despite these provisos, we see this concept of aftercare as working well, both for now and for the future.
  If after these 8-10 weeks your joint should react to the reintroduction of full weight-bearing with swelling and pain, it is not yet ready to bear your full weight. This is an indication for further use of crutches and external treatment measures such as cataplasms, electro and magnetic therapy and in some cases radiation treatment.
  It is most important that you do not become disheartened in this difficult period; after 3-6 months (in rare cases after 9 months), even joints so severely affected by arthrosis improve noticeably and lastingly.

What else can we do?

Supportive drug therapy

• In recent years, injections with hyaluronic acid have shown to be successful in improving the lubrication of a joint, but they are comparatively costly. The recommended course of treatment is a series of 3 to 5 injections (at a cost of about CHF 300 each).
• Supplementation with cartilage builders glucosamine and chondroitin. This combination is currently favoured particularly in the US and in Switzerland. Its pain-relieving effect is said to be similar to that of traditional "rheumatism pills" (such as diclofenac preparations), but with an additional beneficial effect on cartilage regeneration and an absence of unwanted side effects. The recommendation is for a daily dosage of 1500 mg glucosamine sulphate and 1200 mg chondroitin sulphate.

Exercise therapy

The best thing you can for your joints is plenty of movement and exercise while avoiding undue strain, e.g. by loosing weight, wearing well-padded shoes in the initial stages, avoiding long walks/runs on hard surfaces such as asphalt, and similar measures.

• Build up your muscles through gradually increasing endurance training. Suitable activities are "soft straight-ahead sports" such as cycling, walking, Nordic walking and swimming.
• New physiotherapy options such as aqua jogging, which involves intensive circulatory and muscular exercise in the water without undue strain on the affected joint.
• Reflective muscle training with the Galileo-type whole body vibrator: you stand on a tilting plate vibrating at about 40 Hz, compensated for automatically by your muscles. This has already been shown to be a most beneficial exercise for muscles and bones; we are currently investigating positive effects on cartilage regeneration following the above-mentioned surgical procedures.

We also strive to improve our treatment success further, to which end we need your support:

• Please stick to the period of no or restricted weight-bearing as stipulated by us.
• Move your joint as intensively as possible without weight-bearing.
• Keep your agreed follow-up appointments.