The weakness of the knee in the morning may be related to the following reasons: 1, there may be patellar chondromalacia. The so-called patellar tenderness refers to a lesion in the cartilage below the patella, resulting in thinness or complete absence of cartilage, which can cause patients to have very pronounced soreness around the knee and weakness during weight-bearing activities on the ground. In addition, these symptoms are more obvious when the patient gets up in the morning and suddenly puts weight on the ground. 2. This symptom suggests that the patient may have internal inflammation of the knee joint, such as in the case of osteoarthritis of the knee joint, or rheumatic or rheumatoid arthritis attacks, there may be soreness, weakness, and a strange sound in the knee joint when waking up in the morning. 3. osteoporosis. In patients with severe osteoporosis, there is often a symptom of soreness and pain in the lower limbs when they get up in the morning. 4. This condition is likely to be caused by overexertion, for example, if the patient does excessive exercise involving the lower limbs, then after a night’s rest, there may also be soreness and weakness around the knee joint.