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If you are not sure what your knee injury is then why not check out our knee pain symptom checker? Knee injuries can be separated into:
Below we give a brief outline of the common injuries causing knee pain as well as causes of knee pain in children. See the specific knee pain category page for more detailed information.
Acute Knee Injuries
Acute knee injuries are injuries caused by a sudden impact, trauma or twisting of the knee. The athlete will feel instant pain and depending on how bad the injury is may not be able to continue training or exercising.
The knee is likely to swell up either instantly if there is bleeding within the joint or gradually over the following 48 hours if the injury has caused an increase in synovial fluid on the knee such as in a cartilage meniscus injury.
Immediate treatment for acute knee injuries should be RICE; rest, ice, compression and elevation.
Anterior knee pain
Anterior knee pain is pain at the front of the knee. Pain under and around the patella or knee cap will come on gradually and can become severe.
The most common causes of pain at the front of the knee relate to patellofemoral pain. This is pain resulting from the knee cap rubbing repeatedly against the femur. The exact cause of the knee pain is not likely to be bone against bone but some other source which needs to be identified and treated.
Medial knee pain
Medial knee pain is pain on the inside of the knee which is not considered to be an acute knee injury. Medial knee pain usually comes on gradually through over use or as a result of an acute knee injury not healing properly.
The most common causes of pain on the inside of the knee are from injury to the medial cartilage meniscus and the medial ligament. Patellofemoral pain can also be a cause of pain on the inside of the knee as well as at the front of the knee.
Arthritis can also be a cause of medial knee pain. In our medial knee pain section we explain in more detail the varies knee injuries that cause medial knee pain.
Lateral knee pain
Lateral knee pain is pain on the outside of the knee which comes on gradually rather than suddenly as an acute knee injury would.
Iliotibial band friction syndrome is a common over use injury resulting in pain on the outside of the knee. Injury to the lateral cartilage meniscus and lateral knee ligament are common acute injuries caused by trauma, although injury to these structures can occur gradually through over use or poor leg biomechanics.
Check out the lateral knee pain section for more detailed information on injuries causing pain on the outside of the knee.
Posterior knee pain
Posterior knee pain occurs at the back of the knee. Pain at the back of the knee can occur through over use or from an acute knee injury which has failed to heal properly.
One of the more common causes of posterior knee pain is inflammation of one of the hamstring tendons at the point it inserts at the back of the knee, often caused by kick, sprinting or running down steep hills.
A Baker's cyst is a golf ball sized swelling at the back of the knee and is not an injury itself but a result of another injury in the knee joint.
Knee pain in children
Growing children often complain of pain in the knee. Osgood schlatters disease is probably the most well known condition causing pain over the bony prominence at top of the shin bone just below the knee.
Patellofemoral joint pain is also a very common complaint in young athletes, particularly girls and is caused by the knee cap rubbing on the bone underneath resulting in pain and swelling.
Sinding-Larsen-Johansson has symptoms similar to jumpers knee with pain at the bottom of the kneecap and pain can also be referred from a problem in the hip joint in young athletes.
Anatomy of the knee
A simplified view of the anatomy of the knee joint consists of bones, cartilage, ligaments and tendons surrounded by a joint capsule containing lubricating fluid called synovial fluid.
Bones of the knee joint
The knee joint is made up of four bones; the femur (thigh bone), the tibia (shin bone), fibula (outside shin bone) and the patella or kneecap. The femur sits on top of the tibia bone and is cushioned by two semi circular rings of thick cartilage called meniscus. At the ends of bones is a thin, hard covering called articular or hyaline cartilage who's function is to protect the ends of bones and provide a smooth surface for movement. The patella lies in an indentation at the bottom end of the femur known as the intercondylar groove and glides up and down as the quadriceps muscles contract.
There are four main ligaments which stabilize the knee joint and prevent it moving. The lateral ligament on the outside of the knee connects the femur to the fibula and prevents movement out to the side. The medial ligament on the inside of the knee connects the femur to the tibia and is made up of an outer section and a deep section which attaches to the cartilage meniscus on the inside of the knee. This prevents inwards movement of the knee. There are two ligaments which cross over in the middle of the knee called the cruciate ligaments; the anterior cruciate ligament and the posterior cruciate ligament. Together they prevent forwards and backwards movement in the knee joint.
The joint capsule is a thick structure or membrane that surrounds the entire knee. Inside this capsule is another specialized membrane known as the synovial membrane which provides synovial fluid to the joint. The synovial fluid lubricates the joint and provides nourishment. Other structures include the infrapatellar fat pad and bursa which function as cushions in the knee. The joint capsule itself is strengthened by the surrounding ligaments.
Muscles and tendons
The main muscle groups affecting the knee are the quadriceps muscles at the front of the thigh and the hamstring muscles at the back of the thigh. Together they stabilize the knee joint. The quadriceps muscle attaches via a thick tendon to the front of the top of the tibia bone with the patella sitting in the middle of tendon. The patella or knee cap has a significant role not just protecting the front of the knee but it acts as a strong lever for the quad muscles, increasing the forces at the knee joint from the front thigh muscles. The hamstrings attach at the back of the top of the tibia via tendons and bend the knee when they contract.