1, subpatellar fat pad hyperplasia The fat pad fills the gap at the front of the knee joint, which has the function of strengthening joint stability and reducing friction. The cause of fat pad ingrowth may be due to trauma or long-term friction that causes fat pad congestion, hypertrophy and inflammation, and adhesions with the patellar ligament, thus limiting knee joint activities. This injury occurs in people over the age of 30 who walk, hike or squat a lot. Patients may feel pain in the knee joint, which is worse when fully extended, but there is no restriction of joint movement. Symptoms are apparent after exertion. Treatment may first be conservative, with oral NSAIDs. If the impact on the patient’s life is significant, and if there is no significant improvement or even aggravation after 3 months of onset, arthroscopic debridement may be considered. Arthroscopic debridement can be considered, which can significantly relieve the symptoms. It is worth mentioning that if the patient cannot straighten the knee joint, arthroscopic surgery is recommended as soon as possible, otherwise the knee joint will contract over time, leading to serious consequences. 2. Meniscus injury Meniscus injury is a common injury in athletes. When the lower limb is weighted, the foot is fixed, and the knee is slightly flexed, a sudden excessive internal rotation of the knee extension or external rotation of the knee extension (such as the turning and shooting action when playing soccer) may cause a meniscus tear. A meniscal injury will result in a distinct tearing sensation in the knee, followed by joint pain, limited motion, and walking with a limp. Of course, some patients with meniscal injuries experience only mild pain and discomfort that worsens with weight-bearing walking. The joint exhibits swelling and slippage, and some patients have a popping sensation when the joint is moved. Treatment depends on the extent of the injury and whether it is conservative or surgical. Meniscal injuries are usually difficult to heal spontaneously and many patients require arthroscopic surgery. The indications for surgery that I generally recommend are: ① third-degree damage on MRI; ② 1-2 degree damage on MRI that has not improved after 3 months of conservative treatment; ③ embedded knee joint; ④ severe symptoms that affect daily life. 3, knee synovitis including gouty synovitis, traumatic synovitis, choroidal nodular synovitis, etc. The synovial membrane of the knee is one of the main structures that make up the knee joint. Synovial cells secrete synovial fluid, which keeps the cartilage surface of the joint slippery and increases the range of motion of the joint. Injury to the synovial membrane due to trauma or overexertion can produce a large amount of fluid, which increases the pressure in the joint and, if not eliminated in time, can easily cause joint adhesions and affect normal activities. Patients will feel pain, swelling and pressure in the knee joint, and the synovial membrane has a frictional and astringent sound. The most obvious feature of the pain is that the pain in the lower part of the patella will increase when the knee joint is actively and extremely extended, especially when the knee extension movement is done with some resistance, and the pain is also significantly increased when it is passively and extremely flexed. If there is no improvement for more than 3 months, or if there are frequent recurrent episodes, arthroscopic surgery may be considered. 4, osteoarthritis of the knee joint This condition is mostly seen in middle-aged and elderly people, mostly women. Overweight loading is the main cause of the disease. The knee joint will be swollen and painful, and sometimes there will be friction sounds when moving the joint. The knee may have an inversion deformity with medial pain. Treatment is based on the metaplasia of the joint, and joint replacement for severe osteoarthritis of the knee is the most mature treatment internationally. The joint surface replacement surgery performed by Professor Yin Feng of the Department of Joint Surgery at Eastern Hospital has achieved excellent results. For osteoarthritis suitable for arthroscopic surgery, it is only used for cases accompanied by meniscal injury, free body, etc. 5, knee ligament injury The stability of the knee joint is relatively poor when it is slightly flexed, and if it is suddenly subjected to external forces that cause valgus or inversion, it may cause medial or lateral collateral ligament injury. Medial collateral ligament injuries account for the majority of clinical injuries. There is also a common injury is the anterior cruciate ligament or posterior cruciate ligament injury, for such cases, imaging joint stability, need to perform arthroscopic reconstructive surgery. 6, cold In daily life, most joint pain is not caused by trauma, cold (especially constant cold and huge temperature contrast) is the main cause of joint pain. With the development of society, people’s aesthetic and living habits have changed greatly, and people pay more attention to morphological beauty. Even in the cold winter, many people no longer wear thick cotton clothes, but try to reduce the burden on their bodies as much as possible to adapt to modern aesthetic concepts and the fast pace of life. But in the experience of beauty, people have to pay the price of joint damage, because the cold can lead to muscle and blood vessel contraction, causing joint pain. 7, high-intensity exercise or improper exercise Some older people like to hike, but if they do not prepare for the activity or exercise too much, it can also cause joint pain. Especially people who suffer from synovitis or osteoarthritis, more likely to cause joint disease attacks or aggravation. In mountain climbing, when descending a mountain, the weight of the whole body is added to one knee joint, and the pressure on the knee joint is several times greater than when standing normally. The same thing happens when people go up and down stairs. So my advice is that for middle-aged and elderly people, climbing or going up and down stairs, squatting and other movements, should be done sparingly. It is worth mentioning that a half squatting and rotating action of Taijiquan, try not to do. 8, bad walking habits For example, often wearing shoes that do not fit the foot or wearing slippers, high heels walking long distances, will make the knee joint for a long time in an abnormal state of stress, resulting in chronic injury to the knee joint, causing pain. 9, synovial crease syndrome is a kind of patellofemoral joint medial synovial crease hyperplasia, stuck in the patellofemoral joint thus leading to up and down stairs, squatting and other painful conditions. The general x-ray shows no obvious abnormalities in the joint. However, an MRI can show fluid in the patellofemoral joint. In this case, arthroscopic debridement is feasible to remove the synovial folds that have grown and can be restored. 10. Meniscus and free body joint impingement Patients have a sudden inability to straighten or flex the knee joint, with severe pain and inability to put weight on the ground. In such cases, for younger patients, arthroscopic surgery is recommended to contact the impingement. For older patients with poor general health condition, manual repositioning can be tried. 11, patellar dislocation Most often occurs in women, usually with x-leg, i.e. knee valgus. Patients tend to have a larger Q angle, which leads to significant pain when squatting or going up and down stairs. The onset is usually sudden medial tearing pain, followed by significant swelling of the knee joint. Patients will feel a distinct sense of dislocation of the patella, and by the time they come to the hospital, it has often reset itself and thus an x-ray will show normal. The doctor will make a clear diagnosis through physical examination. Magnetic resonance imaging may reveal a significant tear of the medial patellar support band with fluid accumulation. In this case, an arthroscopic triple dislocation of the patella is required.