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Causes of Knee Pain

The knee is the largest joint in your body and it is susceptible to injury. Because the knee is a complex joint, made up of many parts, there are numerous things that can go wrong. Knee pain and damage is commonly caused by arthritis or injuries to the joint.

Topics below cover two common areas of knee problems.

Arthritic Knee

Arthritis is a term that is defined as inflammation of the joint and used to describe over 100 different conditions that can affect the human body. Arthritis affects millions of Americans each year with symptoms including pain, stiffness, swelling, and loss of motion in affected joints.

 The most common form of arthritis that generally affects the knee is osteoarthritis.

 Osteoarthritis, the most common form of arthritis, results in the wearing out of the cartilage that protects the bones in the joints. Once cartilage is damaged or destroyed, cartilage cannot repair or replace itself like many other body tissues. Knee cartilage can be compared to the tread of an automobile tire, very durable but susceptible to wear over time.  As we age, the tread surface slowly erodes until the underlying bone is exposed. This exposed bone can be painful when the joint moves and bears weight. 

 Often the cause of arthritis is unknown, but may develop as a result of injury to the joint, excess body weight, or years of wear and tear on the joint cartilage. There is no known cure. The best that doctors can do for patients is to restore motion and reduce pain.

 Common symptoms of osteoarthritis of the knee

  • Severe knee pain that limits everyday activity
  • Knee pain at night causing sleeplessness
  • Progressive deformity of the leg (bowing of leg inward or outward)
  • Chronic swelling of the knee with morning stiffness
  • Catching or locking of knee
  • Decreased activity
  • Impaired lifestyle
  • Grinding pain during movement
Causes of Knee Pain partial_arthritis Causes of Knee Pain_total_arthritis

Knee Injuries

There are many different types of knee injuries; however, there are a few that are more common than others. Common types of knee injuries include: anterior cruciate ligament (ACL) tears, posterior cruciate ligament (PCL) tears, Medial (MCL) & Lateral (LCL) Collateral Ligament tears, meniscus tears, and cartilage damage.

Many of these injuries can occur from long-term overuse, such as repetitive lifting, pushing, pulling and throwing. For this reason, athletes and skilled workers are particularly prone to knee injuries.


Causes of Knee Pain knee_injury_acl_tear

ACL (Anterior Cruciate Ligament) Tear

The ACL (Anterior Cruciate Ligament) Tear can be injured if the knee is twisted, bent side to side, or hyper-extended during physical activity. The ACL is one of the four main ligaments in the knee. The ligament connects the thigh bone to the shin bone, keeps the knee from hyper-extending, prevents anterior dislocation at the tibia, and stabilizes to help prevent unnatural movement in the joint. Contact sports involving rapid twisting movements may place harsh force on the knee, which can lead to injury.

Symptoms can include swelling of the knee immediately after injury or within 24 hours, may cause a loud popping or cracking sound at the time of the injury, and create the feeling of the knee "giving way."


PCL (Posterior Cruciate Ligament) Tear

PCL (Posterior Cruciate Ligament) Tear is most commonly injured by direct force to the front of the knee, when it is bent. The PCL can also be injured by a direct blow to the outside of the knee joint, such as those that occur during soccer or football.
Symptoms vary depending on the instability in the knee. Patients usually see swelling in the back on the knee and bruising 24 to 36 hours after the injury, pain, excessive swelling and chronic instability.


Causes of Knee Pain mcl_tear

MCL & LCL Tears

The MCL (Medial Collateral Ligament) connects the femur and tibia on the inner side of the leg and resists forces acting on the outer side of the knee.

The LCL (Medial Collateral Ligament) connects the femur and tibia on the outside of the leg and resists forces acting on the inner side of the knee.

The two ligaments create support and stability for the knee. The MCL is more often injured than the LCL as injuries are often caused by a blow to the outer side of the knee, usually seen in contact sports, that stretches/tears the ligaments on the inner side of the knee.

Symptoms of MCL and LCL tears often include pain, stiffness, swelling and tenderness along the inner or outer side of the knee.


Causes of Knee Pain meniscus_tear


A Meniscus Tear usually occurs when the knee is rotating while it is bearing weight. This type of injury often occurs in field sports such as soccer and football.

Symptoms include mild to severe pain, swelling is common at the time of injury, but can develop much later, can cause a popping sound, or the knee may lock, or feel weak.

Cartilage Damage may not heal quickly or at all because cartilage does not have a blood supply to help repair damage. Cartilage acts like a natural shock absorber, preventing both bone on bone contact and providing a smooth, pain-free surface for the bones to glide against. One of the most common and serious types of damage is to the articular cartilage that is between joints.

Symptoms of this articular cartilage damage include swelling, joint pain, stiffness, decreased range of movement and joints that lock or catch.


All patient education materials are provided by and have been reviewed by our Advisory Board of leading Orthopedic Surgeons to ensure accuracy. All materials are provided for informational purposes only and are not intended to be a substitute for medical advice from your orthopedic surgeon. Any medical decisions should be made after consulting a qualified physician.
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