Knee osteoarthritis, also known as degenerative knee osteoarthritis and deformed knee osteoarthritis, is the most common knee pain condition in pain medicine. Depending on its etiology, knee osteoarthritis can be divided into primary and secondary. In primary cases, the cause is unknown, while in secondary cases, there is a clear etiology and the knee injury is only a secondary manifestation of the disease. However, sometimes the two are not easily distinguished. This section will focus on primary knee osteoarthritis.
I. Etiology and predisposing factors
(A) Etiology
The cause of primary knee osteoarthritis is still unknown and may be the result of multiple factors.
1, age clinical findings, the incidence of the disease increases with age, especially in the middle and old age, the prevalence of significantly higher.
It may be related to the following factors.
(1) After middle age, neuromuscular function gradually decreases, resulting in joint damage due to uncoordinated movement.
(2) Progressive increase in the content of inorganic salts in bone as we age, leading to a decrease in the elasticity and toughness of bone. At the same time, the blood flow to the joints decreases, and the articular cartilage becomes thinner, less matrix, and fibrotic due to reduced nutrition, resulting in changes in weight distribution in the joints and making the joint surfaces and articular cartilage vulnerable to injury.
(3) Women before and after menopause, due to estrogen imbalance and increased bone loss, osteoporosis occurs.
2, injury and overuse is one of the more recognized causes.
3, obesity Some foreign statistics found that at the age of 37 years more than 20% of the standard weight of men, the risk of primary knee osteoarthritis is 1.5 times higher than the standard weight of people, while the risk of obesity in women is 2.1 times higher than the standard weight of people with the disease. It may also be related to the posture, gait, and exercise habits caused by increased joint weight bearing and obesity.
4, genetic Many secondary knee osteoarthritis has a clear genetic predisposition.
5, other such as changes in the cartilage matrix of the joint, increased intraosseous pressure, etc.
(ii) Predisposing factors
The following factors may have a role in promoting degenerative changes in the knee joint.
1, inflammatory processes such as rheumatoid disease, inflammation of periarticular and synovial tissue can erode and destroy articular cartilage.
2, metabolic disorders For example, gouty urate deposits, pigmentation of black uric acid urinary xanthosis, accumulation in the articular cartilage, so that the nature of the articular cartilage changes and destruction occurs. Hemochromatosis is similar to its role.
3, biomechanical factors such as joint deformity (for example, knee valgus or knee inversion), so that the joint increased load imbalance, a large distribution of one side, and finally cartilage destruction. Abnormal body forces can also cause internal disorders of the joint. The direction and velocity of the forces acting on the joint are determined, for example, by using a method that envisions the center of force transmission in the joint at one moment. The difference between normal and abnormal conditions of the joint can be found by connecting any point on the joint surface with the center of force transmission of the joint at one moment, perpendicular to the plane of action.
In normal cases, the velocity and direction of the force in contact with the joint surface is parallel to the joint surface. In patients with medial meniscal tears, which arise as a momentary center of force transmission, there is a tendency for the direction of the velocity of the joint force to be transmitted from the femur to the tibia as the joint twists and shifts so that the knee extends. This large contact force causes a meniscal tear and subsequent degenerative joint disease.
The relative compression of the articular surfaces can cause nutritional disorders of the articular cartilage, leading to necrosis of the chondrocytes. This is followed by depletion of matrix protein (PG) polysaccharides, whereupon the articular cartilage is unable to withstand the stresses and shear forces of the back and forth motion of the joint, resulting in degenerative changes. In some experimental animals with knees immobilized by long-term flexion forces, adhesions can occur between the articular cartilage and synovium in the parts of the joint surface that are not in contact with each other. It is possible that the cartilage below the adhesions undergoes degenerative changes because of the cartilage nutritional disorders.
4, the role of hormones acromegaly (acromegaly) patients have obvious changes in articular cartilage. Growth hormone (samototrophin) can stimulate chondrocytes and accelerate and enhance the metabolic activity of chondrocytes. When animals age, growth hormone deficiency is evident, which can cause degenerative changes in chondrocytes and reduced chondrocyte metabolism. In diabetic patients, they are highly susceptible to osteoarthritis because of progressive chondrocyte abnormalities.
5. Chemical injury The whole body or local use of chemical drugs injures the vitality and metabolic activity of chondrocytes. For example, intra-articular injections of glucocorticoids significantly reduce their synthetic activity for periods ranging from a few hours to 1 week or more. When systemic glucocorticoids and immunosuppressants are used, they can likewise cause a decrease in anabolism and loss of PG (glycoprotein). The histological changes are called focal cartilage softening or early osteoarthritis. Intra-articular injection of alkaline drugs (such as nitrogen mustard or thiotepa) can also damage articular cartilage.
6. Repeated intra-articular bleeding In patients with defective coagulation factors, repeated intra-articular bleeding can lead to severe damage to articular cartilage as well as subchondral bone structures. Ionic pigments in the cartilage matrix can change the physicochemical properties of the cartilage, or chondrocytes may engulf large amounts of ionic pigments in the cytoplasm, which can cause lysosomes to release degradative enzymes. One or occasional intra-articular hemorrhage may not present a serious problem.
II. Clinical manifestations
Osteoarthritis of the knee is a common condition in pain clinics, and patients mainly present with joint pain, locking, and functional impairment. In the early stage, the joint pain may only be vague when moving, but as the patient’s condition progresses, the pain gradually worsens and changes to swelling and pain, which is obvious when walking up and down stairs, squatting and standing up, and in severe cases, there may be painful episodes even at rest. In some cases, the pain is manifested by gravelly sounds, joint hollowing and strangulation in the joint cavity during walking. Some manifest as joint stiffness. Severe osteoarthritis of the knee may also be accompanied by joint swelling, peripheral edema, and muscle atrophy.
On examination, there may be pressure points and edema around the knee joint, and the floating patella sign may be positive when there is joint effusion. X-ray examination of the knee joint may show bone formation, narrowing of the joint space, osteoporosis, and loss of the subpatellar fat pad.
Diagnosis
Generally, it is not difficult to make a correct diagnosis of knee osteoarthritis based on the clinical symptoms, signs and knee joint changes of the patient.
The international diagnostic criteria for osteoarthritis of the knee and the diagnostic criteria for osteoarthritis of the knee established by the American College of Rheumatology in 2001 are described below.
(A) International diagnostic criteria for osteoarthritis of the knee
1. Clinical diagnostic criteria
①Knee pain for most of the time in the first month.
(ii) There is bone friction sound.
③Morning stiffness <30min.
④Age ≥38 years old.
⑤ Knee examination shows bony hypertrophy. The diagnosis of osteoarthritis of the knee can be made if ①②③④ or ①②⑤ or ①④⑤ are met.
2. Clinical, laboratory and radiological diagnostic criteria.
①Knee pain for most of the anterior month.
②X-ray film shows bone flab on the edge of the joint.
③Joint fluid examination is consistent with osteoarthritis.
④Age ≥40 years.
⑤ Morning stiffness <30min.
⑥There is a bone ringing sound when the joint moves. If ①② or ①③⑤⑥ or ①④⑤⑥ are met, osteoarthritis of the knee can be diagnosed.
(II) American College of Rheumatology
The American College of Rheumatology established the diagnostic criteria for osteoarthritis of the knee in 2001
1. Patients with knee pain have 3 of the following 7 items
① Age ≥ 50 years.
② Morning stiffness <30min.
③Bone rattling sound during joint movement.
④Knee examination shows bony hypertrophy.
⑤ There is bone pressure pain.
⑥No obvious synovial warming.
⑦There is bone redundancy formation on radiological examination.
2.Patients with knee pain have 5 of the following 9 items
① Age ≥50 years.
②Morning stiffness <30min.
③There is bone rattling sound when the joint moves.
④Knee examination shows bony hypertrophy.
⑤Bone pressure pain.
⑥No significant synovial warming.
⑦ESR<40mm/h.
⑧Rheumatoid factor (RF) <1:40.
⑨ Synovial fluid with signs of osteoarthritis.
V. Treatment
The treatment of osteoarthritis of the knee aims at disease education, pain relief, prevention and delay of structural changes in joint tissues, and restoration of its normal function.
(A) General treatment
1, disease education knee osteoarthritis is mostly caused by degenerative changes, the general prognosis of patients is good. While relieving the patient’s ideological concerns, the patient should be given the necessary life guidance. Make them realize that it is very important to control diet, reduce weight, pay attention to vitamin and mineral supplements (including calcium), and adhere to moderate functional exercise. In addition, attention should be paid to the use of appropriate shoes and insoles, as well as crutches and knee pads. Also, pay attention to self-protection in daily life to avoid overworking and catching cold.
2. Coordinated muscle movement and muscle strength enhancement can effectively reduce joint pain symptoms. In order to enhance the muscle strength and endurance around the joint, maintain and enhance the range of motion of the joint, and improve the patient’s ability to perform daily life, it is very beneficial to perform appropriate physical exercise. Aerobic exercises and quadriceps strengthening exercises have obvious effects in relieving pain and improving function.
(1) Quadriceps strengthening training: the method is: the patient takes a sitting position, drops the lower leg, hangs a 2-3kg weight at the ankle joint, consciously makes the quadriceps contract and makes knee extension and flexion movement. Quadriceps contraction exercise can increase the contraction force of quadriceps, promote blood circulation around the knee joint, prevent local muscle atrophy and reduce the loss of bone calcium.
(2) Muscle isometric exercises, which can enhance muscle strength, are performed about 4 times a day.
For patients undergoing physical therapy, if limb pain occurs during exercise or pain persists for more than 15min after exercise, the intensity and number of exercises should be reduced appropriately and increased after the patient gradually adapts.
3.Food therapy More calcium-rich foods, such as milk, soy products, seafood and green vegetables, etc., can play a positive role in replenishing the calcium needed by the normal body and reducing the loss of body calcium, especially in preventing bone calcium loss in women before and after menopause.
(B) drug therapy
1, non-steroidal anti-inflammatory drugs (NSAIDs) At present, NSAIDs are still the basic drugs for the treatment of pain in patients with osteoarthritis of the knee. In recent years, newly developed cyclooxygenase-2 (COX-2) specific inhibitors such as: celecoxib, rofecoxib, its therapeutic effect is comparable to traditional NSAIDs, while the side effects are significantly reduced. The safety of long-term use of acetaminophen (paracetamol) is significantly higher than that of other traditional NSAIDs, and has been recommended by European expert groups as the first choice of oral analgesics, especially for the elderly, but care should be taken to prevent its damaging effects on the liver.
2.Analgesics and opioids
①Ampitin (diacetin): The advantage is that it can be used in combination with NSAIDs. It is reported that the drug can promote cartilage repair.
② Tramadol: It is a weak opioid analgesic and can be chosen for patients who are not suitable for NSAIDs.
③Oxycodone hydrochloride controlled-release tablets (Oxycontin, Oxycontin): it is a strong opioid, a pure opioid receptor agonist, with no capping effect on analgesia.
3.Glucosamine sulfate (GS): It is a physiological substance necessary for the biological metabolism of chondrocytes, and chondrocytes use GS to synthesize large molecules of mucopolysaccharide, which constitute an important part of cartilage matrix and maintain the morphology and function of cartilage together with type II collagen fibers.
4.Calcium preparations and vitamin D can prevent bone loss and osteoporosis, delay the development of osteoarthritis and improve the quality of life of patients. The more commonly used are calcium D, alpha D3, calcium gluconate, calcium bone, etc.
5, psychotropic drugs can improve the patient’s depression and anxiety and other mental changes, long-term application of antidepressant drugs can not only relieve the depression caused by chronic pain, but also increase the function of the central nervous system of downstream pain inhibition. Commonly used are amitriptyline, doxepin, diazepam, etc.
(C) Nerve block therapy
Nerve block therapy is currently a better method for the treatment of knee osteoarthritis, and its therapeutic effect is exact. It also has the significance of differential diagnosis for hip and ankle joint-derived knee pain.
1. Intra-articular injection Injecting local anesthetic drugs into the joint cavity can be used to determine whether the cause of pain is intra-articular or extra-articular by the degree of pain relief.
Previously, a mixture of local anesthetic and glucocorticoid was injected into the joint cavity. The drug formula is 5-10 ml of a mixture of 0.5% lidocaine or 0.25% bupivacaine and 5 mg of dexamethasone, which is injected once a week, 3-5 times for a course of treatment, usually one course of treatment can be effective. However, because glucocorticoids can increase the chance of local infection, they are no longer commonly used.
At present, the more recognized and effective method at home and abroad is to inject sodium hyaluronate directly into the joint cavity, and the commonly used dose is 20mg of sodium hyaluronate, once a week, 5 times for a course of treatment.
The mechanism of action may be related to the following factors.
(i) Inhibition of inflammatory mediators (e.g. cytokines, prostaglandins).
(ii) Stimulation of cartilage matrix and endogenous hyaluronic acid production.
(iii) Inhibition of cartilage degradation.
④Direct protection of nerve endings that sense injury.
⑤Lubricating and elastic effects, which can relieve stress between tissues, protect articular cartilage, and promote healing and regeneration of articular cartilage.
Intra-articular injections should be performed with strict aseptic protocols, as the consequences of intra-articular infection in the knee can be quite serious. It should also be done gently to avoid damage to the articular cartilage.
2.Local painful point block The tendon and ligament attachments around the knee joint with conscious pain or pressure pain should be blocked one by one, 2-3ml per point.
Commonly used methods are.
①Inject 2 to 3ml of a mixture of 0.25% to 0.5% lidocaine, vitamin B12 and 2ml of angelica liquid at each point.
② Depo-Provera 7mg (or Asagil 0.9), 0.5%~1% lidocaine, vitamin B12 0.5 mg mixture, 2~3 ml per point injection.
3.Joint cavity irrigation Suitable for patients with fluid in the joint cavity. The method is: after the joint fluid is extracted through the joint cavity puncture, 50 ml of saline equivalent to body temperature is repeatedly and rapidly injected and suctioned. Once a week, for 2 to 5 times in a row, the pain symptoms can be significantly reduced.
4.Zeikawa injection therapy The operation method of knee zeikawa therapy is the same as local pain point block.
(iv) Physiotherapy
The more commonly used physical therapy methods are TEHNS, acupuncture, massage, etc.
(v) Surgery
It is suitable for patients with long-term conservative treatment, intractable pain with disability and severe destruction of the knee joint as shown by X-ray. Common surgical procedures include arthroplasty, osteotomy, arthroscopic removal of free body, autologous chondrocyte implantation (ACI), etc.