Pain at the back of the knee can be acute (sudden onset) or chronic (gradual onset). It can also be referred from other areas such as the lower back or from within the knee joint itself. Here we explain the most common causes of pain at the back of the knee.
On this page:
- Acute injuries (sudden onset)
- Chronic injuries (gradual onset)
- Emergency first aid
- Should I see a doctor?
- Important injuries not to miss!
Acute (sudden onset) pain at the back of the knee
Acute posterior knee pain is often from a tear or strain of a tendon which joins the muscle to bone. However, a chronic knee injury can become acutely painful from time to time, especially with overuse.
The biceps femoris is one of the hamstring muscles. A tear or strain can occur to the tendon which inserts at the top of the tibia or shin bone at the back of the knee. It is more common in sprinters or sports involving kicking. Symptoms include a sudden sharp pain in the back of the knee. There may be swelling, tenderness or heat at the site of injury.
Symptoms of an avulsion strain are similar to that of a hamstring tendon strain above, however, with an avulsion, the tendon is torn and pulls a small piece of bone away with it. This injury is known to be particularly painful with swelling at the point of injury. If suspected an X-ray is needed to confirm the diagnosis.
Chronic (gradual onset) pain at the back of the knee
Knee pain which occurs gradually where the patient is unlikely to be able to pinpoint the exact time the injury occurred. These injuries often start out as a gradual 'niggle' but eventually become more chronic and can be more difficult to treat.
Knee joint swelling
Swelling within the knee can be enough to cause pain and tightness behind the knee. A full knee assessment should be done to identify the root cause of any effusion (swelling). Previous injuries can often be the cause of chronic knee swelling and development of a Baker's Cyst.
Gastrocnemius tendinopathy or tendinitis is inflammation or more likely degeneration of the tendon of the calf muscle causing pain at the back of the knee. This is an overuse injury which is more common in runners and sprinters. Treatment involves reducing the pain and inflammation followed by a full rehabilitation and exercise program to restore the muscle and tendon to full function.
Biceps femoris tendinopathy or biceps femoris tendonitis is inflammation or degeneration of the hamstring tendon at the point where it inserts at the outside back of the knee. Symptoms include tenderness and swelling at the point of injury which is likely to have come on over time. Stiffness in the morning or after sitting for long periods is also a symptom.
The Popliteus is a small muscle located at the back of the knee joint. The muscle or tendon can be torn suddenly, especially from twisting activities. Or pain can occur gradually from inflammation or degeneration of the tendon, known as tendinopathy.
A Baker's Cyst or Popliteal cyst is a swelling that protrudes out the back of the knee. It is often about the size of a golf ball but can vary over time. A sensation of pressure in the back of the knee and the patient will have difficulty bending the knee.
Referred knee pain
Posterior knee pain can be caused by injuries or dysfunction in the lower back and hips. Sciatic pain from a number of causes radiates down into the back of the leg, knee and lower leg. The slump test is one test which should be done when examining pain at the back of the knee to identity referred pain at the back of the knee.
The Posterolateral corner of the knee consists of a number of structures. It is a less common cause of pain at the back and outside of the knee. Symptoms can include any of the following; pain and swelling at the back and outside of the knee, tenderness on the outside knee and instability.