Your knee is a complicated piece of machinery. Permitting you to flex and extend your leg while running, maintaining the health of your knees should be taken seriously. Pain that appears at the back of a knee can mean a handful of different possible injuries. Your ability to identify the sources of pain quickly may mean preventing further injury and beginning treatment so training can soon be resumed.
Hamstring Muscles
Hamstring injuries can be a source of pain at the back of the knee. The hamstring is composed of three muscles: the biceps femoris, semimembranosus and the semitendinosus. Each muscle spans the back of your legs, attaching behind the knees and extending up to the buttocks. Straining the lower portion of any one of these muscles can cause pain in the back of the knee.
Baker's Cyst
Also known as a popliteal cyst, Baker’s cyst occurs when the bursa, a fluid-filled sac that reduces friction on the knee, becomes damaged. This causes swelling to occur through increased production of fluid. Symptoms include pain and swelling behind the knee and sometimes an inability to bend the knee. Causes of a Baker's cyst may occur because of a tearing of the meniscal cartilage or as a result of the onset of osteoarthritis.
Meniscus Injuries
The meniscus refers to two pieces of cartilage that provide support for the knee. When tension is formed through stretching or through twisting, the meniscus distributes friction from the knee joint to the femur and tibula. The two pieces of cartilage are known as the lateral and the medial meniscus. When the medial is damaged or torn, pain at the back of the knee is the result, especially when squatting.
