A triangular-shaped, movable flat bone, our patella, can be felt in the area of our knee. The patellofemoral joint evolved to accommodate bipedal walking. It is “responsible” for our ability to walk and move. However, our patella can sometimes have a temper tantrum, for example, patellar instability. What happens if the patella becomes unstable? First of all, there is pain in the anterior region of the knee, with the medial aspect of the knee being the most common. The pain can be aggravated by excessive activity, especially when going up and down stairs, climbing or prolonged flexion and extension activities. 1, playing “soft leg”: when walking with weight, the knee joint appears momentarily weak, unstable feeling, and sometimes even fall down. 2. Pseudo-insertion: This is a momentary involuntary restriction disorder that occurs when extending the knee. Patellar instability (unstable patella) is a common cause of anterior knee pain, a common disorder of the patellofemoral joint, and an important cause of chondromalacia of the patella or osteoarthritis of the patellofemoral joint. Second, what tests may be needed for patellar instability? 1, X-ray: is a common means of diagnosing patellar instability. 2, arthrography: double imaging of the knee joint can not only observe changes in the patellar cartilage, but also compare and examine the supporting ligaments on both sides of the patella as well as diagnose synovial wrinkle wall syndrome. 3, Arthroscopy: This is an invasive examination method. 4, CT or MRI examination: the use of CT and MRI makes the diagnosis of patellofemoral joint instability more accurate and avoids the image overlap and distortion of ordinary X-rays. The specific type or types of examination applicable needs to be judged by the competent doctor according to the actual situation of the patient. How to treat patellofemoral instability? (1) Non-surgical treatment: (1) Restriction of activities: restricting certain activities in the patient’s daily life, such as ascending and climbing, can reduce the load on the patellofemoral joint and reduce patellofemoral joint wear. (2) Quadriceps exercises: Subacute or chronic patellar instability is often accompanied by significant quadriceps atrophy and weakening of muscle strength, especially the weakening of the medial femoral oblique head muscle strength, which can further aggravate the instability of the knee joint, causing joint swelling and aggravating symptoms, so quadriceps exercises should be strengthened. (3) Brace therapy: Brace therapy for patella has the effect of limiting and stabilizing the patella, it is used for acute patients, or when participating in a sport or activity more. Long-term wear can cause local discomfort and lead to quadriceps atrophy. (4) Drug therapy: Non-steroidal anti-inflammatory drugs can reduce the symptoms of osteoarthritis in the patellofemoral joint. (2) Surgery: The purpose of surgery is to improve the patellar force line, restore the normal fit of the patellofemoral joint and reconstruct the knee extension device. The specific surgical method needs to be chosen by the doctor according to the actual situation of the patient.