Osteoarthritis of the knee

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Classification according to ICD-10
M17 Gonarthrosis (osteoarthritis of the knee joint)
ICD-10 online (WHO version 2019)
Localization of knee arthrosis (right knee, schematically from the front)

With knee osteoarthritis or osteoarthritis of the knee is referred to a wear of the cartilaginous articular surfaces of the knee joint .

Affected joint sections

The knee joint consists of three joint sections, all of which (pangonarthrosis) or individually can be affected. If the kneecap joint (femoropatellar joint) is worn, it is often referred to as retropatellar arthrosis (arthrosis in the knee joint, behind the kneecap). If the inner or medial compartment of the femorotibial joint is affected, there is medial osteoarthritis of the knee, or varus osteoarthritis of the osteoarthritis of the knee, which often occurs at the same time . The osteoarthritis of the outer or lateral femorotibial compartment is the lateral gonarthrosis, or with simultaneous knock-knees malposition, the valgus gonarthrosis.

Kneecap joint (femoropatellar joint)

Femoral patellar osteoarthritis

The picture on the right is a horizontal sectional view through the patella plain bearing and the lower end of the thigh , the femoral condyles. The image was created with an NMR device. You can see the thin layer of cartilage (the kneecap is shifted outwards), the kneecap slide and the back surface of the kneecap. This reacted with osteophytes , bone extensions , to the changed load conditions: The bone adjacent to the cartilage is compacted.

At the sliding bearing of the kneecap, there is often an uneven load distribution in this joint section. The extensor muscles of the thigh can react within a short period of time (14 days) to a limited load capacity of the knee, the abdomen of this muscle (quadriceps, the four-headed) quickly loses strength with the result that the load is shifted to the back of the kneecap.

The cartilage on the back of the kneecap is up to 7 mm thick, making it the thickest layer of cartilage in the body. This cartilage is not supplied with blood, but only nourished by the synovial fluid. At this thickness this can no longer work through diffusion alone. This is where a flexing process comes into play: under load, synovia (joint fluid) is pushed in and out of the cartilage. This ensures sufficient exchange as long as the bearing load remains in the physiological range. The system can handle neither too much nor too little pressure. If this pressure deviates far enough from the ideal range, cartilage nutrition disorders occur . The cartilage degenerates, frays, becomes rough: the plain bearing of the kneecap begins to rub. One speaks of unmasking the cartilage. The first symptom here is pain on the stairs, when getting up from a crouch or when sitting for a long time. Popularly these symptoms are called “theater knees” because they used to occur in people who shuffled their feet after the first act of a play.

Medial compartment

NMR image of medially accentuated knee osteoarthritis, seen from the front

In this picture it can be seen that the cartilage in the inner (medial) area of ​​the joint has been used up and the bone located under the cartilage is compacted in the medial area of ​​the tibial head. This is called "sclerosed" or "eburnised". Osteophytic reactions have occurred in both the lateral and medial parts of the joint . The body tries to reduce the pressure on the articular cartilage by widening the contact surface. In the higher resolution, the muscles around the knee can be clearly seen in this image, but this is not shown in the reduced image. The "height reduction of the medial joint space" (clinical jargon, what is meant is the height reduction of the cartilage) leads to a malalignment of the knee joint, the leg deviates into the varus or O-malposition. The plumb line from the femoral head through the ankle joint migrates from the center of the knee towards the medial compartment, the contact pressure in the already worn part of the joint continues to increase, and the clinical picture itself worsens.

Irritant effusion, NMR image of knee osteoarthritis in longitudinal section.

The display technique is a little different than in the pictures above, the irritant pour - in principle water - is shown here in white. You can see the distribution of the synovial fluid ( synovia ) and osteophytes , especially at the upper pole of the kneecap .

A healthy knee needs a valgus or X position of 8 degrees. Damage to the inner meniscus is particularly common in competitive athletes (e.g. soccer players). If the meniscus is injured, surgical removal of the torn part is recommended. This makes sense because the meniscus tissue has the same surface hardness as the cartilage of the joint. If the fragment remains in the knee, it will quickly lead to cartilage damage.

If this tissue is surgically removed, however, the contact area of ​​the thigh roller on the tibia head is reduced. In conjunction with the previous meniscus damage, this causes cartilage damage or a defect in the thigh roll. These abrasion processes lead to the medial joint space collapsing, the knee deforming in the sense of a bow-leg or varus deformity. This causes the plumb line , which falls from the center of the femoral head through the knee to the ankle, is shifted further into the central area of ​​the knee. This area is more and the outer area less stressed. The wear and tear in this medial part of the knee, which has already been damaged, progresses, the misalignment becomes stronger, the load distribution shifts further, the circle closes. The final stage is varus gonarthrosis , which can often only be treated surgically.

Lateral compartment

X-ray of lateral gonarthrosis (above) compared to a normal knee joint (below)

Just like the inner area of ​​the knee joint, the outer area can also change degeneratively. Here, too, the abrasion processes lead to a self-reinforcing deformation, this time the supporting line of the leg moves to the outer area of ​​the knee, resulting in a knock knees or valgus malalignment. Most of the time, the ligaments are looser in valgus deformities than in bowlegs. This makes surgical treatment more difficult.

The X-ray shows the narrowing of the outer knee joint gap and also the knock-knees position. An extension can be seen on the shin head . The x-ray signs of osteoarthritis of the knee are usually clear, so that a magnetic resonance examination is usually not necessary.


Conservative forms of therapy

The knee is often affected by injuries. Every painful condition, even temporary, leads to a weakening of the thigh muscles. The first, essential step is to rebuild the extensor muscles of the thigh with a suitable training program. Electrical stimulation and electrical muscle stimulation are useful here and do not damage the knee or the patient. Another important measure, especially at the beginning of the illness, can be a doctor-patient consultation. Here, the patient can be explained by the attending physician about the disease, its course and the therapeutic options, and the options for participating in the therapy can be discussed. Other conservative forms of therapy, the costs of which are covered by statutory health insurances in Germany, are z. B.

  • Relief in the form of cushioning (e.g. buffer heels)
  • Weight reduction and walking aids such as walking sticks , forearm crutches , rollators and wheelchairs
  • Acupuncture , although study results clearly show that it is of no use, and the American guideline for osteoarthritis therapy gives a clear recommendation against acupuncture.

Alternative forms of therapy

Other forms of therapy, the costs of which are usually not covered by the statutory health insurances in Germany, because there is no scientific proof of effectiveness, are z. B .:


Nonsteroidal anti-inflammatory drugs (NSAIDs) according to WHO I are suitable for pain relief and as an anti-inflammatory (anti-inflammatory) agent -Mandatory), each alone or in combination. However, all drugs have a number of side effects and should therefore be prescribed carefully and carefully. At this point at the latest, an appointment with a suitable specialist in orthopedics or orthopedics and trauma surgery is indicated, if necessary in combination with other pain therapists. Common contraindications or a narrow and possibly time-limited indication for level I may exist. a. in diseases of the gastrointestinal tract such as B. ulcers on the stomach and duodenum, but also in diseases of the cardiovascular system such. B. high blood pressure, myocardial infarction, thrombosis and pulmonary embolism as well as generally older people from around 60 years. In this case, or if the effect is insufficient, drugs of level WHO II / III can be a suitable alternative in addition or in exchange. In principle, drug therapy is indicated on the one hand for remaining symptoms during or after specialist conservative and / or surgical therapy or for those cases in which this therapy is not possible or only possible later, e.g. B. as bridging during waiting times in the operating theater or for contraindications for further therapies (e.g. electrotherapy for cardiac pacemakers or intra-articular injections for Marcumar patients).


It is technically relatively easy to inject medication into one knee. Careful skin disinfection and hygiene are important here. A germ carried to the knee can lead to serious infections - up to sepsis  .

Crystalline cortisone is often used for these intra-articular injections . This quickly relieves the irritation, the pain and the effusion are significantly less. However, nothing changes in the generally poor condition of the joint. In addition, there is the emery effect that the crystals exert on the cartilage.

Another therapy to relieve pain by improving joint lubrication is the injection of hyaluronic acid , the effectiveness of which, however, was rated as modest in a meta-analysis from 2003. The IGeL-Monitor of the MDS (Medical Service of the Central Association of Health Insurance Funds) rates the IGeL hyaluronic acid injection in knee osteoarthritis as "generally negative". Compared to placebo and no injections, it has been shown that pain can be reduced somewhat and the function of the joint slightly improved. However, mild adverse events at the injection site are common after hyaluronic acid injection. Serious side effects also occur - their frequency is unclear due to poor reporting in the studies.

Operative therapy methods

Joint-preserving operations

If a knee joint is damaged but not yet completely destroyed, one will always try to operate in a way that preserves the joint. There are a number of methods for doing this, such as

Arthroscopic joint debridement

This form of therapy is carried out very frequently and is used to restore smooth joint surfaces and eliminate meniscus damage. It becomes arthroscopic , i.e. H. minimally invasive approach. However, it remains unclear whether the joint debridement can have a positive effect on osteoarthritis in the knee joint. Studies have shown that arthroscopic therapy for osteoarthritis of the knee (debridement) is not superior to arthroscopic placebo therapy (joint flushing) or conservative therapy consisting of physiotherapy and strengthening exercises. An advantage of the arthroscopy could not be determined. The intervention is only indicated if there is further damage to the knee joint in addition to the gonarthrosis, which can be repaired arthroscopically.

Corrective osteotomy

With the leg axis correction, more stressed parts should be relieved and, conversely, less stressed parts should be more stressed. So z. B. a bow-leg deformity ( genu varum ) to an increased burden on the inner compartment and a knock-leg deformity ( genu valgum ) to an increased burden on the outer compartment. If there is then also increased cartilage damage in the more heavily loaded compartment, the indication for a surgical change in loading can be made in the form of an osteotomy . So z. B. in the case of a bow-leg with damage on the inside, the leg axis is corrected in a valgus direction, thus relieving the more affected medial compartment at the expense of the lateral compartment. Requirements for this are u. a. in addition to a rather younger age (otherwise an endoprosthesis), an incipient or at best moderate cartilage damage in the respective inner or outer compartment and a corresponding misalignment of the axis. The adjustments can be carried out at the end of the thigh near the knee or under the tibial plateau near the knee on the shin. After the bone has been severed ( osteotomy ), the correction is carried out by folding down with removal of a bone wedge ("closed wedge") or by opening it ("open wedge"), which then z. B. is fixed by a plate screwed into the bone (plate osteosynthesis ). After the bone has healed, the metal plate is usually surgically removed later ("metal removal").

Knee joint denervation

In the case of advanced knee osteoarthritis, it is possible to achieve a significant reduction in pain by means of a knee joint denervation, and in many cases even complete freedom from pain. Here, pain-conducting nerve fibers above and below the knee joint are microsurgically switched off. This operation is a symptomatic therapy: the osteoarthritis, i.e. the wear and tear of the joint, remains unaffected. If the denervation is successful, the use of an artificial joint replacement can be avoided or even delayed, but the chances of success and the value of the intervention compared to other procedures have not yet been adequately evaluated scientifically. In view of the good results of endoprosthetics, this procedure has so far rarely been used.

Since the afferent nerve fibers emerging from the joint capsule are partially and selectively severed, complications are minor, and numbness in the knee area rarely occurs. As a rule, a denervation test is carried out beforehand using local anesthesia in order to avoid unnecessary operations.

Even with chronically painful knee joint prostheses, denervation can take place after prior testing, since postoperative neuromas are assumed to be the cause of pain for postoperative pain conditions with the correct position of the prosthesis . Denervation also very often occurs around the kneecap if the back of the kneecap is not replaced as part of a knee joint endoprosthesis.

Implantable joint relief spring

Since the end of 2011, another joint-preserving therapy option has been available in Germany with the implantation of a relief spring system. It is indicated for patients who suffer from pain and loss of knee function due to medial osteoarthritis of the knee and for whom conservative therapies such as pain relievers and knee splints do not bring any improvement. Depending on the severity of the knee osteoarthritis, the relief spring can be an alternative to joint replacement, especially for younger sufferers, or at least significantly delay its need. A relief spring attached to the side of the joint reduces the medial compartment by up to 13 kg with every step. The spring is compressed in extension and thus takes over part of the applied load. In the knee flexion phase, the spring has no function and does not exert any tension. The reduction in the stress on the joints is intended to significantly alleviate the pain of osteoarthritis and counteract the progressive degeneration and loss of function.

The system, consisting of a femur and a tibial base and the relief spring placed in between, is implanted subcutaneously and extracapsularly on the medial side of the knee and positioned above the medial collateral ligament. The base bodies are anchored to the tibia or femur with several bone screws: The femoral base comes under the vastus medialis muscle on the femur, the tibial base anteriorly on the medial tibia. The connection to the spring is made via a ball joint, which is supposed to maintain the normal range of motion of the knee (50 ° varus-valgus , 155 ° flexion-extension,> 60 ° internal-external rotation). The procedure does not require opening of the joint capsule or bone removal or alteration and is therefore completely reversible.

The knee implant set is CE-certified under the name KineSpring® System in Europe , the manufacturer announced the 500th implantation worldwide in October 2013. No statements can yet be made about shelf life, late complications and long-term results. A first study on 100 patients showed that the severity of the knee pain improved by 60% after one year (p <0.001), 76% of the patients achieved at least a 30% improvement in knee pain. A significant improvement was achieved in all WOMAC criteria: a 56% improvement in pain, 57% improvement in function and an improvement of 39% in stiffness (each p <0.001). The percentage of patients who achieved at least a 20% improvement in the WOMAC criteria was 74% for pain, 83% for function, and 67% for stiffness. Six patients underwent another operation during the follow-up period: they received a knee replacement surgery or a high tibial osteotomy. An ongoing international multicenter study (GOAL trial) is currently investigating the effectiveness of the relief spring implantation in comparison to the high tibial osteotomy.

Joint replacement operations

Total endoprosthesis of the knee on the model, made of a cobalt - chromium - molybdenum alloy, cemented, uncoupled with a solid polyethylene (PE) inlay and without rear stabilization

If the condition of the knee makes a joint-preserving procedure no longer sensible, a joint replacement, a knee prosthesis , will be chosen . This means that the damaged structures in the knee are replaced by a metal surface modeled on the knee. There are partial prostheses that only replace one area of ​​the joint, as well as uncoupled or coupled prostheses that then also replace the ligamentous apparatus.

Occupational disease

Gonarthrosis has been recognized as an occupational disease in Germany under certain conditions since July 1, 2009 and is listed as number 2112 in the list of occupational diseases. The prerequisite is an activity on the knees or under comparable knee load, which comprises at least 13,000 hours in the entire working life and at least one hour per work shift. An increased risk is assumed for miners, farm workers, floor and tilers and shipyard workers, and it is assumed for construction workers and forest workers on the basis of an individual assessment.

There are only a few scientific studies on osteoarthritis of the knee under increased occupational strain on the knee. The only cohort study that was carried out as part of the Framingham study showed an accumulation of osteoarthritis of the knee in men who reported that they had “at least moderate occupational activity with frequent squats”. The cause is assumed to be an "increased pressure force on the knees during professional activity or a comparable knee load on the articular cartilage in the retropatellar and tibiofemoral joint". It is therefore expected that the osteoarthritis first manifests itself patellofemoral and only then in the rear (dorsal) sections of the tibiofemoral joint parts, with wear of the posterior horns of the inner and outer meniscus as a possible initial stage. On the other hand, osteoarthritis predominantly in the main stress zone of the knee joint is not considered to be work-related.

The current clinical prerequisites are chronic complaints in the knee joint with limited extension or flexion and radiologically confirmed osteoarthritis (at least grade 2 according to Kellgren). An indication of the assumption of an occupational disease is the bilateral occurrence of osteoarthritis of the knee, while overweight, frequent occurrence of osteoarthritis of the knee in the family, osteoarthritis also in other joints ( polyarthrosis ), misalignments of the axes and other pre-arthrosis are indications of competing causes and therefore against the assumption of one Talk about occupational disease.

The assessment of the reduced ability to work (MdE) depends on the extent of the functional impairment; in the case of a unilateral knee joint prosthesis , at least 20% is assumed.

In addition, there has been an occupational disease after meniscectomy or partial meniscus resection in certain cases with proven occupational overload for years (No. 2102).

Degree of disability

According to the 2012 edition of VersMedV, partial endoprostheses are rated on one side with a GdB of at least ten and on both sides with at least 20, with so-called full dentures this is 20 or 30. These values ​​are assigned with a clinically good result, otherwise higher ratings may also be possible. The older AHP 2004 and 2008 differentiated only between unilateral and bilateral restoration and not the type of implant, at that time even higher rates of GdB 30 and GdB 50 were in effect, so now a downgrade. Restriction of movement in the knee joint is assessed depending on the extent of the restriction: slight disturbances in the ability to bend when the right angle is reached with free extension are rated on one side with 0-10 and on both sides with 10-20. Moderate restriction (e.g. E / F 0-10-90) increases the values ​​to 20 or 40 (one-sided / both-sided), with an even greater restriction 30 or 50. In the case of proven cartilage damage - also in the kneecap area - grade II IV results in persistent irritation (the pure imaging evidence without clinical symptoms is not sufficient) on one side without movement restriction a GdB of 10-30 and with movement restriction a GdB of 20-40. In the VersMedV there is no explicit specification for a bilateral finding.

See also


Web links

Individual evidence

  1. Wolfgang Miehle: Joint and spinal rheumatism. Eular Verlag, Basel 1987, ISBN 3-7177-0133-9 , p. 175.
  2. Guideline of the American Academy of Orthopedic Surgeons AAOS
  3. ^ GH Lo et al: Intra-articular hyaluronic acid in treatment of knee osteoarthritis: a meta-analysis. In: JAMA. 2003, 290, pp. 3115-3121 ( German summary )
  4. IGeL-Monitor, evaluation of hyaluronic acid injections in knee osteoarthritis . Retrieved October 18, 2018.
  5. JB Moseley, K. O'Malley, NJ Petersen et al: A controlled trial of arthroscopic surgery for osteoarthritis of the knee . In: N. Engl. J. Med. Band 347 , no. 2 , July 2002, p. 81-88 , doi : 10.1056 / NEJMoa013259 , PMID 12110735 .
  6. ^ A. Kirkley, TB Birmingham, RB Litchfield et al: A Randomized Trial of Arthroscopic Surgery for Osteoarthritis of the Knee . In: N. Engl. J. Med. Band 359 , no. September 11 , 2008, pp. 1097-1107 , doi : 10.1056 / NEJMoa0708333 , PMID 18784099 .
  7. ^ A. Kirkley, TB Birmingham, RB Litchfield et al: A Randomized Trial of Arthroscopic Surgery for Osteoarthritis of the Knee . In: N. Engl. J. Med. Band 359 , no. September 11 , 2008, pp. 1097-1107 , doi : 10.1056 / NEJMoa0708333 , PMID 18784099 . quoted from D. Einecke, MMW
  8. springerlink.com
  9. ^ AL Dellon: Pain Solutions . Lightning Source, La Vergne 2007.
  10. AL Dellon, MA Mont, DS Hungerford: Partial denervation for the treatment of painful neuromas complicating total knee arthroplasty. In: JN Insall, WN Scott (Ed.): Surgery of the knee . Saunders, Philadelphia 2000, pp. 1772-1786.
  11. KD Brandt et al: Etiopathogenesis of osteoarthritis. In: Medical Clinics of North America. 93, 2009, pp. 1-24. doi: 10.1016 / j.mcna.2008.08.009 , PMID 19059018
  12. M. Timothy, Farshid Guilak: The Role of Mechanical Loading in the Onset and Progression of Osteoarthritis . In: Exercise and Sport Science Reviews. 33 (4), pp. 195-200, 2005.
  13. DR Wilson et al .: The measurement of joint mechanics and their role in osteoarthritis genesis and progression. In: Rheumatic Disease Clinics of North America. 34, 2008, pp. 605-622. doi: 10.1016 / j.rdc.2008.05.002 , PMID 18687275
  14. Joel A. Block, Najia Shakoor: The biomechanics of osteoarthritis: Implications for therapy. In: Current Rheumatology Reports. 11, 2009, pp. 15-22. doi: 10.1007 / s11926-009-0003-7
  15. Anton G. Clifford et al: The KineSpring® Knee Implant System: an implantable joint-unloading prosthesis for the treatment of medial knee osteoarthritis. In: Medical Devices: Evidence and Research. 6, 2013, pp. 69-76. doi: 10.2147 / MDER.S44385 , PMC 3663478 (free full text).
  16. Moximed Announces 500th implant of KineSpring System for Knee Osteoarthritis . ( Memento of the original from April 13, 2014 in the Internet Archive ) Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice. Press release Moximed Inc., October 15, 2013. @1@ 2Template: Webachiv / IABot / www.moximed.com
  17. ^ Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) - General Description. American College of Rheumatology (ACR), accessed April 9, 2014 .
  18. Nicholas J. London et al .: Bridging the osteoarthritis treatment gap with the KineSpring Knee Implant System: early evidence in 100 patients with 1-year minimum follow-up . In: Orthopedic Research and Reviews. 2013: 5, pp. 65-73, doi: 10.2147 / ORR.S48629
  19. M. Schiltenwolf: Gonarthrosis recognized as an occupational disease. In: Orthopedics communications. 01/2010, pp. 44-47.