Patellofemoral joint cartilage injury

　　First, etiology

　　Any factor that affects the normal secretion of joint synovium or the squeezing mechanism of joint cartilage, and hinders the normal activity of the joint, can cause damage to the joint cartilage.

　　Second, pathogenesis

　　1. Acute or chronic trauma:It may directly impact the cartilage, destroying the collagen fiber reticular arch structure in the cartilage. It can also directly cause a tangential fracture of the cartilage. Chrisman has been studying the relationship between trauma and patellar chondropathy from a biochemical perspective for many years. He found that within 2 hours after cartilage is impacted by trauma, the concentration of free arachidonic acid in the cartilage can increase by 4 times. Arachidonic acid is a major component of phospholipid membranes and a precursor of prostaglandins. Its products are converted into prostaglandin E2, which stimulates AMP cycle, releases tissue protein kinase, and breaks the chain of chondroitin sulfate and protein binding in the cartilage matrix, causing the cartilage matrix to lose, leading to cartilage softening. Metabolic products enter synovial fluid to cause synovitis, and inflammation stimulates synovium to release a large amount of enzymes, further damaging the cartilage, creating a vicious cycle.

　　2. Fatigue damage of the patellofemoral joint:Long-term abnormal friction and compression on the patellar cartilage, especially repeated squatting, jumping, carrying loads, and twisting in the flexed position of the knee joint, can cause excessive or uneven stress between the patella and femoral condyle, making the patellar cartilage prone to injury and leading to patellar chondropathy.

　　3. Unstable patellofemoral joint:Common unstable factors such as high or low patella position, abnormal knee Q angle, patella tilt, tibial torsion deformity, and abnormal development of patella or femoral condyle, can cause patellar chondropathy due to abnormal patella position or alignment, or abnormal contact surface and contact stress between patella and femoral condyle. Many scholars have done a lot of work on the stress distribution and stress testing of the patellofemoral joint, including high contact pressure theory, low contact pressure theory, uneven pressure distribution theory, and increased patellar bone pressure theory, all of which are supported by experiments. However, whether the pressure is too high, too low, or unevenly distributed, as long as the pressure exceeds or does not reach the normal bearing range of patellar cartilage, it can lead to cartilage degeneration.

　　4. Pathological changes:The main pathological changes of patellar chondrodysplasia are the softening, yellowing, cracking, peeling off, ulcer formation of the patellar cartilage, as well as synovitis, increased secretion, patellar fasciitis, and inflammatory changes and hyperplasia or contraction of the patellar parietal ligament. The fallen cartilage fragments may become joint mice in the joint cavity, causing knee locking.

　　Athletes with patellar chondrodysplasia most commonly have lesions on the medial aspect, followed by the central area (60° contact area) and the medial area. However, Ficat reported that the lateral area has the highest incidence.

　　Rijnds divides the cartilage lesions of patellar chondrodysplasia into four degrees. Degree Ⅰ is the superficial cartilage layer with fine cracks, softening of the lesion area cartilage, mild swelling, and yellowing, which is roughly equivalent to the injury of the first layer of chondrocytes (resting layer). Degree Ⅱ is the injury of the second layer (transition layer) and the third layer (mast cell layer) of the cartilage, with visible superficial cracks. Degree Ⅲ is the injury of the fourth layer (calcified layer) of the cartilage, with deepening cracks, reaching the subchondral bone locally, and cartilage fragments peeling off from the surface. Degree Ⅳ is the injury reaching the subchondral bone, with ulcer formation, and the complete destruction of the local cartilage. There is often gradual erosion of healthy cartilage around the lesion area, and adjacent cartilage often has varying degrees of degeneration.

　　It can be complicated with joint loose bodies and joint effusion, patellar chondrodysplasia. Patellar chondrodysplasia is often not serious in the early stage, and rest or taking general painkillers can alleviate it. The lesion develops continuously in a 'hidden state' until it develops into patellofemoral arthritis. In severe cases, the extension and flexion of the knee joint is limited, and it is not possible to stand on one leg. In the late stage, when patellofemoral osteoarthritis has formed, there is significant destruction of the cartilage and subchondral bone in the lesion area, and the cartilage has no ability to regenerate and repair. In addition, this disease is prone to complications such as meniscus injury and traumatic arthritis.

　　Firstly, general symptoms:The main symptom is posterior patellar pain, which occurs during activity or semi-squatting. Initially, it is a feeling of acid fatigue and discomfort, which later develops into persistent or progressive pain. Often, pain is more pronounced when starting activity, decreases after activity, and worsens when activity ends or when resting. This kind of pain is sometimes very characteristic and is often described as 'toothache-like pain'. It is particularly noticeable when climbing stairs, especially when going down or downhill, and there is often a complaint of 'the knee is weak' and 'almost fall down'. Sometimes there are symptoms of joint locking.

　　Secondly, signs:In terms of signs, the following characteristics are mainly present:

　　1. Pain when grinding the patella:Mostly positive, with an occurrence rate of almost 100%.

　　2. Resistance pain when pushing the patella:Also positive, when the patella is pushed towards the distal end, the quadriceps muscle contracts, and pain under the patella is positive.

　　3. Single-leg semi-squat test:It is mostly positive. This sign is one of the most significant and diagnostic signs of patellofemoral cartilage disease. Quan Mianyu reported that the positive rate of this sign is 100%, and Chen Shiyi reported that it reaches more than 93%.

　　4. Quadriceps atrophy:It is relatively obvious, especially the medial head is more significant.

　　5. Knee joint effusion sign:It is mostly positive. The floating patella test can help with diagnosis. When the amount of knee joint effusion is less than 30ml, the effusion-induced bulging test can be used to detect it. Joint puncture can extract a light yellow transparent fluid, and occasionally a cloudy joint fluid can be extracted.

　　6. Patellar periarticular tenderness:When patellofemoral cartilage disease is accompanied by peripheral soft tissue inflammation, pain can be felt when scratching around the patella with the nail of the index finger.

　　7. Patellar crepitus:After the cartilage softening and peeling off of the patella, the patellar cartilage surface is uneven, and when the knee joint moves, the patella can be felt as a rough crepitus behind it. The characteristic of this crepitus is that it appears when the knee joint moves to a certain fixed angle, and it remains unchanged after multiple repetitions, which is caused by the rough and uneven friction of the cartilage. The opportunity to appear the crepitus is not many, but many authors believe that the rough crepitus at a certain fixed angle behind the patella is of diagnostic significance.

　　The occurrence of patellofemoral cartilage injury in middle-aged and elderly people has both intrinsic and extrinsic factors. The intrinsic factor is the degeneration of the joint cartilage itself, which is related to factors such as age. The extrinsic factor is the chronic injury to the joint cartilage caused by mechanical factors. The main way to prevent the occurrence of patellofemoral cartilage injury is to reduce the continuous pressure on the patellofemoral joint and improve the nutrition of the cartilage. The following measures can be referred to:

　　1. Actively fully move the joint:It should be done under non-weight-bearing conditions. For example, lie flat on the bed and actively extend and flex the knee joint. Do this twice a day, in the morning and evening, for 10 minutes each time. Fully moving the joint can stimulate all parts of the patellofemoral joint surface, and the nutrients of the synovial fluid can be evenly permeated into the cartilage tissue, which can also enhance the lubricating effect of the joint.

　　2. Prevent the continuous pressure on the patellofemoral joint surface:The pressure on the patella in a flexed knee position is relatively large, which is easy to damage the joint surface. It is necessary to avoid the continuous pressure on the patellar joint surface from a sustained squatting position.

　　3. When using plaster cast fixation or lower limb traction treatment, it is necessary to actively exercise the quadriceps muscle:The quadriceps muscle can move the patella up and down when it contracts and relaxes, which is conducive to the nutrition penetration of the cartilage and the reduction of the continuous pressure on the patellofemoral joint surface.

　　4. When there is discomfort or pain in an undefined location in the knee joint, it is necessary to consider the possibility of early patellofemoral cartilage injury:It is important to rest and treat promptly to prevent the aggravation of joint cartilage degeneration.

　　1. X-ray findings:Taking routine X-ray films is of little significance for diagnosis, but choosing to take patellar axis films at different flexion angles of the knee can observe the shape of the patella, the degree of ossification of the subchondral bone of the patella cartilage, and measure certain indices of the patella, such as the patellar angle, patellar depth index, patellar index, groove angle, and overlap angle. The lateral X-ray film of the knee joint can detect abnormal patellar position. Normally, the length of the patella (P) is equal to the length of the patellar ligament (PT). When PT exceeds 15% of P or exceeds 1cm, it is considered as a high patella.

　　2. MRI Examination:It can be found that there are areas of patellar cartilage stripping and ulceration.

　　1. Increase protein intake:Protein is very beneficial for the recovery of body tissues. It is recommended to consume an additional 10 grams of protein per day, which can be provided by 200 milliliters of low-fat yogurt, 300 milliliters of skim milk, 30 grams of lean meat, poultry, or fish, 60 grams of beans, or 40 grams of low-fat cheese.

　　2. During the recovery period of sports injuries, it is also important to supplement vitamin C and zinc:Vitamin C and zinc also help the body to repair. Citrus fruits, cauliflower, green peppers, tomatoes, potatoes, and strawberries are rich in vitamin C. Foods rich in zinc include oysters, crabs, black chicken, yogurt, milk, almonds, peanuts, cashews, and chickpeas.

　　3. During the recovery period of sports injuries, you can also try turmeric powder and wasabi:More and more scientific evidence shows that turmeric has the same analgesic effect as Valdecoxib and Celecoxib without any side effects. Therefore, nutrition experts suggest sprinkling a little turmeric powder on salads, soups, vegetables, or meats and poultry. Eating wasabi is also good, because wasabi also contains a small amount of turmeric powder.

　　4. During the recovery period of sports injuries, whole wheat bread, pasta, and rice can be considered to be eaten with a large amount of vegetables:Experts say that these things are rich in rough fiber and can produce a feeling of fullness, but not high in calories. Therefore, they can keep the mouth busy without the worry of gaining weight.

　　1. Patellar Cartilage Cutting Technique:Including superficial cartilage ablation, cutting cartilage to bone and bone drilling.

　　2. Patellar Osteotomy:After cutting away the diseased cartilage, where there is a large area of bone exposed (2-3cm), the adjacent synovium or a layer of fat pad can be used to flip and suture over the exposed bone surface.

　　3. Patellar Resection:If the patient is older and has severe symptoms with a large area of bone exposed (more than 3cm), and the relative femoral condyle cartilage wear is also significant, and the patient cannot undergo patellar osteotomy, it may be considered to perform a patellar resection.