What is “tenderness”? How is it related to chondromalacia patella? The so-called “weak legs”, also known as “weak legs” and “weak knees”, describe a symptom, i.e., when walking normally or walking up and down stairs, you suddenly feel that your knee joints can’t take the effort, and you feel like kneeling down. It is a feeling of weakness and wanting to go down on your knees, which is sometimes accompanied by severe pain and a real fall. Chondromalacia patella occurs in the cartilage between the patella and the femur in young people. As the cartilage surface of the patella becomes uneven, sometimes accompanied by congenital dislocation of the patella, the cartilage degenerates prematurely and becomes defective, which causes the knee joint to become tender. Does chondromalacia patella always present with knee pain? What are the characteristics of the pain? Chondromalacia patellae is usually characterized by knee pain, which can be mild or severe and can last for many years. Hidden pain at the back of the patella and on the inside of the knee is the most common symptom, which is aggravated by exertion or after walking up or down stairs. In severe cases, pain can be present around the entire patellar circumference. When synovitis is present, the pain is more widespread and there is pain in the joint space. If the patella is pushed to compress the cartilaginous surface of the patella, there can be pressure pain, and there is also a distinct pressure point anterior to the medial femoral condyle. What are the other typical symptoms of chondromalacia patella? Gradual onset, anterior knee pain, early manifestations of pain after strenuous exercise (such as climbing, 100 meters running, basketball, soccer, etc.), going up and down the stairs and squatting and standing up with effort, pain aggravated, alleviated after rest. Soreness, weakness, limp legs. There may be rattling and friction sensation when the joints move. Continued development can occur with joint swelling and pain even when walking on level ground. What is interlocking phenomenon? When does it occur? Knee interlocking is a very common clinical condition that can be painful due to muscle spasm for either mechanical or functional reasons. During the movement of the knee joint, there is a sudden restriction of flexion and extension, as if it were stuck, and there is significant pain, i.e. interlocking pain. Knee interlocking phenomenon is mostly seen in meniscus injuries, intra-articular free bodies in the knee joint, and even includes synovial disease of the knee joint (such as synovial folds), Hoffa disease, intra-articular ligament injuries of the knee joint, cruciate ligament cysts, acute popliteal tendonitis, patellar cartilage chondromalacia (most often due to the cartilage is not smooth), patellofemoral joint alignment abnormality, patellar subluxation or semi-dislocation, and gouty stones. Graft detachment, intra-articular tumors (e.g., lipoma), etc. Is chondromalacia patella always associated with joint effusion? Not all cases of chondromalacia patella are associated with joint effusion. When the patellar cartilage is damaged alone, there is no joint effusion. When osteoarthrosis of the patellofemoral joint develops at a later stage, synovitis occurs at this time, and joint effusion may occur. If the disease duration is long, the quadriceps muscle atrophy may appear.