Outside Knee Pain (Lateral Knee Pain)

Lateral knee pain on the outside of the knee

Most injuries in a sport which cause pain on the outside of the knee are gradual onset, where the athlete may not be able to pinpoint an exact time when the injury occurred as they might do with an acute joint sprain or muscle injury.

On this page:

  • Most common
  • Less common
  • Emergency first aid
  • Should I see a doctor?
  • Important injuries not to miss!

Most common causes of lateral knee pain

Iliotibial band syndrome

One of the most common causes of pain on the outside of the knee is Iliotibial band syndrome. It commonly affects runners with symptoms of pain and inflammation on the outside of the knee which comes on sometime during a run. Pain usually eases with rest only to return again when training resumes.

The iliotibial band is a long tendon which runs down the outside of the thigh from the tensor fascia latae muscle (TFL) and inserts at the top of the tibia (shin bone). When the TFL muscle and band become tight the tendon rubs against the bone on the outside of the knee becoming inflamed. Read more on:

Lateral meniscus injury

A lateral meniscus tear is an injury to the cartilage meniscus which provides cushioning and support to the knee joint. This can be a sudden onset acute knee injury but gradual onset pain from wear and tear or degeneration of the cartilage is common. Pain will be felt along the joint line on the outside of the knee and usually when squatting. There may be noticeable swelling but not always. Read more on:

Less common causes of outside knee pain

Patellofemoral pain

Patellofemoral Pain Syndrome (PFPS) occurs when the patella (kneecap) is out of alignment and rubs on the femur bone underneath. Symptoms include an aching pain in the knee joint, with tenderness and swelling mostly at the front of the knee, around and under the patella but can develop towards the outside of the knee. Symptoms are often worse when walking up and down hills or when sitting for long periods. Read more about:


Osteoarthritis is wear and tear on the knee joint resulting in degeneration of cartilage and eventually bone. A deep aching pain is felt, usually on the inside of the knee but it can also affect the outside knee area. Pain is worse after exercises and swelling and/or joint stiffness is common.

Biceps femoris tendinopathy

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.

Superior (proximal) tibiofibular joint sprain

The tibiofibular joint is the point in the knee where the tops of the lower leg shin bones (tibia and fibula) join. Dislocation of the joint occurs most commonly when the athlete sustains an impact or fall with the knee in a fully bent position. Symptoms include pain and swelling on the outer surface of the shin with the top of the fibula bone being more prominent just below the outer surface of the knee.


Synovitis occurs when the synovial membrane which lines and lubricates the knee joint becomes inflamed. Symptoms include swelling or stiffness in the joint which may develop following another injury, or from arthritis or gout.

Referred pain

Pain may be referred into the knee from problems elsewhere in the body, particularly sciatic pain from the lower back and hip. Read more on:

Other causes of knee pain which MUST not be missed

Peroneal nerve injury

Symptoms of a peroneal nerve injury, also known as peroneal neuropathy are caused by a direct impact to the outside of the knee. Specific symptoms which might distinguish a peroneal nerve injury from a straightforward contusion include numbness or tingling in the front and or side of the lower leg with weakness lifting the foot upwards and outwards. In severe cases, foot drop will occur where the foot cannot be lifted up enough to enable normal walking.

Slipped capital femoral epiphysis

This is a fracture of the growth plate (epiphysis) at the top of the thigh bone. It is more common in boys aged 11 to 16 years old and develops gradually over time. Symptoms include pain in the hip and groin which can radiate into the knee.

Perthes' disease

Perthes' disease is a hip condition which affects children, most commonly aged between four and eight. Symptoms of tiredness and groin pain are common symptoms along with a noticeable limp. Medical help is needed to diagnose this condition as early as possible to try to prevent any future problems.