What structures make up the knee joint?

Knee pain can signify a minor sprain but could also point to a severe joint injury. A knee injury may be serious if you experience severe knee pain, walking with a limp, or you experience rapid swelling.
Knee pain can signify a minor sprain but could also point to a severe joint injury. A knee injury may be serious if you experience severe knee pain, walking with a limp, or you experience rapid swelling.

Knee injuries are common in people with an active lifestyle. Knee pain can signify a minor sprain but could also point to a severe joint injury. Most knee pain can be cared for at home with rest and simple treatment. But some knee injuries have severe damage to the structures in the joint. These injuries need proper treatment for full recovery. Knowing the most common knee injuries will help you avoid joint damage and disability.

The knee is perhaps the most complicated joint in the human body. It bears all your weight when standing and absorbs the shock of landing when running or hopping. Its complex structure makes it prone to many types of injury.

The knee joint consists of three bones — the thigh bone (the femur), the shin bone (the tibia), and the knee cap (the patella). The other bone of the leg, the fibula, is not a part of the knee joint. The bones are held together by several ligaments and are covered with cartilage to provide smooth movement. Between the bones are the menisci to give a cushioning effect. Tendons connect the muscles to the bones above and below the knee.

What are the most common knee injuries?

The knee is a strong joint built to bear your body's weight. Athletic pursuits like running and some sports cause serious knee injuries. Tears of the ligaments and menisci and fractures and dislocation of the bones are common knee injuries.

People with active lifestyles often have knee pain. It is important to distinguish between minor strains and severe knee injuries.

Anterior cruciate ligament (ACL) tear

This is an injury of one of the ligaments connecting the thigh bone to the shin bone. It is injured by rotational forces — twisting while the feet are planted on the ground. Basketball, soccer, skiing, and football are the sports that commonly cause this injury. You can also tear the anterior cruciate ligament by landing awkwardly.

ACL tears are often not very painful. You may feel a pop at the time. The typical feature of an ACL injury is a feeling of instability and swelling. You feel your knee could give way at any moment.

Posterior cruciate ligament (PCL) tear

These happen with an impact to the front of the knee while it is bent. PCL tears are common in vehicular crashes and contact sports. They're usually partial tears and may heal on their own.

Collateral ligament injuries

In this injury, two collateral ligaments are damaged by a direct blow to the sides of your knees. These are often sports-related injuries. Medial collateral ligament injury is more common. Your knee could become unstable and have long-lasting effects, including osteoarthritis.

Meniscal tears

These are usually sports-related injuries. The menisci tear and are displaced inside the knee. Apart from pain, movement of the knee is restricted. The knee may be locked in meniscal injury.

Tendon injuries

The two tendons at the front of the knee are the quadriceps tendon and the patellar tendon. These can be injured or torn by running, jumping, and falls. Tendonitis is an inflammation of the tendons. Repeated jumping, as in basketball, can cause tendonitis of the patellar tendon. This condition is called jumper's knee.


The knee cap (patella) is the most frequently fractured bone at the knee joint. The ends of the tibia and femur are less commonly injured. These fractures result from intense impacts and usually happen after falls from heights and vehicular crashes.


The knee joint bones are displaced from their positions relative to each other. This usually follows high-velocity impacts.

How can you know your knee injury is serious?

If you follow an active lifestyle, you're used to knee pain and swelling. These are common in all runners and sports enthusiasts. Most such injuries are minor and recover with simple treatment. But if you have any of these symptoms, you should be warned:

  • Severe pain
  • Inability to move the knee
  • Walking with a limp
  • A lot of swelling, with a change in the shape of your knee
  • Hearing a pop at the time of the injury
  • Feeling your knee give way. This could mean complete tear of a ligament
  • Rapid swelling. This could be caused by the joint filling with blood

Any of these signs should alert you that your knee injury is serious. Such injuries may not heal on their own and need specialized treatment. 

Knee pain to worry about

Even if you didn't have a hard impact while on the field and the injury seems mild, watch out for these signs.

  • Your knee pain persists for a long time
  • Your knee swelling goes on increasing
  • The shape of your knee is changed

If you have a high fever, feel hot and shivery, and have redness or heat around your knee, your knee could be infected (septic arthritis) in addition to being injured.

Diagnosing severe knee injuries

If you feel your knee injury is serious, you should consult an orthopedic surgeon. These physicians have specialized training in bone and joint injuries. They may be able to diagnose your injury by examining your knee in their clinic. Sometimes, they may need to ask for:

X-rays. X-ray pictures are usually taken from two directions (front and side) and can show fractures and dislocations.

Scans. Computed tomography (CT) or magnetic resonance imaging (MRI) scans give a detailed view of the structures inside and around your knee. Your doctor will find these scans helpful in diagnosing your knee injury and planning the treatment.

Arthroscopy. Your doctor will insert a tube with a light at the end into your knee joint through a cut made in the skin. Your doctor can see the structures inside your joint. Torn menisci, ligaments, inflammation, degeneration, and tumors can be seen. Some injuries can be repaired by arthroscopy, too. 


Medically speaking, the term "myalgia" refers to what type of pain? See Answer

RICE for non-severe knee injuries

If you don't have any of the signs of a severe knee injury, you can try the RICE treatment. RICE stands for rest, ice, compression, and elevation.


Avoid putting weight on your injured knee.


Use ice in cold packs for 20 minutes at a time. You can do it many times a day.


Wrap your injured knee in an elasticized bandage. This will apply pressure around the joint and reduce swelling.


Use pillows or bolsters to lift your knee higher than your heart while resting. This will let the swelling drain away.


Knee injuries frequently happen to people with an active lifestyle. Some knee injuries leave the knee joint unstable. This can reduce your performance and enjoyment of sports in the short term. You might suffer from early degenerative changes and osteoarthritis in the long term. Proper treatment of serious injuries is crucial.

Most knee injuries are minor and recover with rest, ice application, compression, and elevation (RICE). But be alert if you have severe pain, can't walk without a limp, feel your knee giving way, are unable to move your knee, or have a lot of swelling. These signs tell you that your knee injury is serious. You should consult an orthopedic surgeon soon to get proper treatment and get back to full activity. 

Health Solutions From Our Sponsors

Medically Reviewed on 4/26/2022

American Association of Orthopedic Surgeons: "Common Knee Injuries."

John Hopkins Medicine: "Knee Pain and Problems," "Ligament Injuries to the Knee."

Journal of Orthopaedics: "Review: Medial collateral ligament injuries."

National Health Service: "Knee Pain."