Without our knees, we wouldn’t be able to straighten or bend our legs—it is the menisci, ligaments, tendons, and muscles that guide and stabilize our movements so that we can walk at all. In healthy people, the bones of the knee joint are covered with a whitish layer of cartilage several millimeters thick, which is what makes pain-free movement of the knee joint possible in the first place. As we age, wear and tear can lead to cartilage loss, but improper weight-bearing can also cause excessive strain on the cartilage. The result is pain—and limited movement. Even if the entire kneecap pops out or twists, the advice of a knee specialist is needed. The editorial team of the Leading Medicine Guide spoke with Dr. Björn Drews, a specialist in knee surgery and sports orthopedics practicing at St. Vinzenz Clinic in Pfronten, Allgäu, about precisely these topics.
When a person weighing eighty kilograms climbs a flight of stairs, the knee joint is subjected to three times that weight—meaning approximately 240 kilograms of pressure is placed on the knee joint, which, incidentally, is the largest joint in our body. Healthy joint cartilage acts like a shock absorber and is therefore essential for smooth movement. Given these stresses, it’s no surprise that many people develop problems specifically with the cartilage in their knees.
“You have to distinguish between accident-related cartilage damage, general wear and tear, and a genetic predisposition to cartilage loss or degeneration,” says Dr. Björn Drews as he begins our conversation. “In the case of accident-related cartilage damage—for example, a torn cruciate ligament, where a great deal of energy is transmitted to the cartilage—cartilage changes and symptoms may not appear until later. Treatment options then depend on the extent of the damage. Damage that is only superficial does not necessarily require surgical treatment,” explains Dr. Drews.
Methods of Cartilage Transplantation
There is a wide range of options when it comes to cartilage regeneration. One of these is cartilage transplantation: “To perform a cartilage transplant, the patient’s own cartilage cells are cultured in the lab and then reintroduced into the knee. A transplant is most suitable for younger patients who have localized cartilage damage. To generate the patient’s own cartilage, cartilage cylinders are punched out of a non-weight-bearing area of the knee during surgery and then enriched, for example, with the patient’s own blood. They are then cultured in a laboratory on various carrier materials—the matrix—to form either a large cartilage graft or tiny beads, a process that takes approximately three to seven weeks. In a second, usually open surgical procedure, the harvested cartilage cells are implanted into the patient’s damaged area. “This then gives rise to new cartilage that is very similar to natural cartilage,” says Dr. Drews, explaining the procedure.
Innovative Procedure: The AutoCart Method
Patients for whom a cartilage cell transplant is not an option due to age or the size of the defect can instead be successfully treated with the AutoCart method using their own tissue in a single surgery. “The AutoCart method is based on the so-called cartilage chip technique, which was developed a good forty years ago and has been continuously improved and refined ever since. For this procedure, the excised cartilage is cut into tiny pieces and mixed with the patient’s own blood—specifically, platelet-rich plasma—to create a kind of cartilage gel. This is then reintroduced into the patient, and this procedure requires only a single surgery, which is, of course, much less invasive and more patient-friendly overall,” explains Dr. Drews regarding this modern transplantation method.
In general, transplants are regulated by the German Medicines Act. The patient must be no older than fifty years of age, and the cartilage damage must cover an area of at least 2.5 cm². Only certain areas of the knee may be repaired via transplantation.
“The underlying causes of cartilage degeneration must always be treated as well. If there are leg misalignments such as bowlegs or knock-knees, these must also be corrected to prevent further damage,” says Dr. Drews, explaining the complexity of cartilage treatment.
Patellar Dislocation—When the Kneecap Pops Out
Even a slight movement can cause the kneecap to suddenly pop out of its groove. “There are various causes here as well. In the case of an accident, this naturally happens quickly—for example, due to an improper twisting motion. Often, however, the condition is rooted in a developmental predisposition. Many younger people, especially girls, are affected during their growth phase. “The key to treatment here is the correct diagnosis,” Dr. Drews points out. In any case, it is crucial to take action, as the kneecap popping out causes permanent damage to the cartilage, which can ultimately lead to knee osteoarthritis. “In some patients, the kneecap pops out 300 to 400 times over the course of time,” says Dr. Drews, who, interestingly, also explains that the anatomy here is very similar to that of dogs, among whom terriers in particular often suffer from patellar dislocation.
“Patellar dislocations need more attention. The correct diagnosis is very important to avoid adverse outcomes, such as osteoarthritis developing as early as age thirty,” warns Dr. Drews.
“If the groove on the thigh is too shallow, imagine trying to balance one egg on top of another. Recurring pain is a warning sign that the kneecap may be unstable. However, surgery should be performed no later than after the second dislocation of the kneecap. If the retaining ligament—which is unstable in these cases—is not repaired, dislocations will occur repeatedly. The supporting ligament can be reinforced with a tendon from the patient’s own body. If the gliding groove is too shallow, it must be reshaped, which is done through a fairly complex surgical procedure,” says Dr. Drews, explaining the necessity of surgery.
X- and O-Leg Deformities
A misalignment of the leg axes in the form of X- or O-legs can have genetic causes, be due to unilateral wear and tear, or result from a poorly healed fracture in the past. “In these cases, there is naturally enormous pressure on the cartilage, which then wears down more quickly. The treatment options depend on the extent of the damage. In cases of advanced wear and tear, the goal should always be to rebuild the cartilage and correct the misalignment,” states Dr. Drews.
What is pseudoarthrosis?
When a bone fracture occurs, the new bone tissue that is supposed to form requires phosphate and calcium. Calcium absorption, in turn, is promoted by vitamin D. However, if both of these building blocks are lacking, a fracture cannot heal properly. Pseudoarthrosis refers to bones that heal poorly or not at all. Instead of bone, connective tissue forms. “Especially if a patient has suffered a comminuted fracture or an open fracture due to a fall, and blood flow to the fractured area is no longer optimal, e.g., due to diabetes or cigarette smoking, pseudoarthrosis may develop. A bacterial infection can also contribute to this condition. Bone regeneration is then severely impaired,” explains Dr. Drews. Depending on the cause, an initial conservative treatment approach may involve the administration of vitamin D and calcium, along with exercise, to stimulate blood flow, which ensures that sufficient nutrients are transported to the fracture site.
Pseudoarthrosis is diagnosed when a bone fracture has not healed even after more than six months.
“Early-stage pseudoarthrosis or delayed fracture healing can also be treated with shock wave therapy, which can serve as an alternative to immediate surgery in the early stages. This can be done on an outpatient basis,” explains Dr. Drews. The shockwave device is focused on the area to be treated, and the shockwaves are transmitted into the body at a frequency of two to four hertz. Some discomfort is to be expected, but the doctor controls this by reducing the energy level or by stopping the treatment. Up to three sessions are required for this therapy, and a total of between one thousand and two thousand shock waves are administered to achieve the desired results.
In cases of pseudoarthrosis, high-energy shock waves are used, as greater forces are necessary for successful treatment.
“In surgical treatment, the malformed connective tissue must be removed. The missing bone must then be replaced, for which the body’s own bone material—for example, from the pelvic bone—is usually harvested. In some cases, an external fixator is also necessary to promote healing,” says Dr. Drews.
Research is on the right track
“We’re on the right track when it comes to research. Therapies for cartilage regeneration are successful, and joints can now be preserved for much longer. However, many procedures are expensive and are not adequately reimbursed by health insurance policies. Furthermore, procedural regulations—for example, regarding transplants—are often too strict, meaning that some patients cannot be helped in these cases,” concludes Dr. Drews as we wrap up our conversation.
Dr. Drews, thank you very much for these interesting insights into our knee joint! Anyone wishing to contact our specialist directly can do so via his profile page on the Leading Medicine Guide.
