My leg suddenly can't straighten; it hurts when I try to straighten it, and there's a painful tendon in the back of my knee. What should I do?

The leg suddenly cannot straighten, and pain occurs when attempting to do so; there is also pain in a tendon behind the knee. For this condition, it's important first to address the underlying cause. Inability to straighten the leg is mainly due to knee joint disorders, such as meniscus injury, osteoarthritis, or bone spurs leading to flexion deformity of the leg. Additionally, inflammation of the leg fascia causing soft tissue spasms can also result in the symptom of an inability to fully extend the leg. Therefore, symptomatic treatment may help alleviate these issues.

1. Warmth: Patients should first be advised to avoid trauma and cold exposure. It's important to keep the legs warm in daily life and avoid repeated bending and excessive weight-bearing activities. Applying a hot water bottle or other heat therapies daily can increase local blood circulation in soft tissues, reduce inflammatory factors, and relieve leg pain.

2. Exercise: Engage in moderate physical activity and actively perform flexion and extension exercises of the joints, especially non-weight-bearing exercises such as riding an exercise bike while lying down, leg elevation, or jogging. These activities help strengthen muscles and ligaments around the joint, prevent muscle atrophy, and gradually restore leg joint function.

3. Medication: If the patient experiences significant leg pain, treatments such as warm compresses, acupuncture, or moxibustion may be used. In addition, non-steroidal anti-inflammatory drugs (NSAIDs) like ibuprofen, celecoxib, etoricoxib, or loxoprofen sodium can be taken orally as prescribed by a physician to relieve tendon pain. The choice of medication should consider the patient’s gastrointestinal condition and provide effective pain relief when taken appropriately.

4. Nutritional supplementation: While improving knee and ankle joint function, it's beneficial to supplement calcium and vitamin D appropriately, which can also help improve symptoms. If symptoms persist despite these measures, the patient should seek medical evaluation and further treatment at a hospital.