A pain or stiffness in the knee can affect the quality of sleep. So if you've had an exhausting night with excruciating knee pain, you can guess what the next day will be like, for sure!

But what really causes knee pain at night and what is the signal your body is giving you?

1. Osteoarthritis

As a form of arthritis that becomes more common with age, knee osteoarthritis occurs when the cartilage that protects your joints begins to weaken. This can happen from straining the knees, too many activities and carrying heavy weights.  

2. Chondromalacia

Chrondromalacia, or damage to the cartilage below the kneecap, often causes pain when going up or down stairs or when sitting. Usually, this symptom comes from an injury, such as a broken kneecap or a sprain from running, soccer, or cycling.

3. Tear of the meniscus

People who play sports are at risk for a meniscus tear, a common knee injury that can occur when rapid rotations or strong strain cause a tear in the knee tissue. The injury begins with a popping sensation, pain, swelling and inability to move freely.

4. Runner's knee syndrome

A mild pain around the front of the knee that is accompanied by a popping sound, especially when you move the knee could be runner's knee syndrome. It can happen from running or walking too much, or if you have tight tendons.

Source: Livestrong