The knee joint connects the thigh bone to the tibia and fibula of the lower leg. It is one of the biggest joints in the body comprised of bones and other important structures such as tendons, ligaments, cartilage, and fluid sacs. Knee pain may be the result of a sports injury, a slip or fall, work-related that may cause a ruptured ligament or torn cartilage or due to medical conditions such as arthritis, gout, and infections.
Damage or degeneration to any of these structures can impair or restrict your ability to walk, kneel, bend, and twist. Pain and loss of mobility in your knee can impair your ability to do normal activities.
The location and severity of knee pain depend on the cause of the problem.
Signs and symptoms that sometimes accompany knee pain include:
- Swelling and stiffness
- Redness and warmth to the touch
- Weakness or instability
- Popping or crunching noises
- Inability to fully straighten the knee
Knee Problems and Injuries
- Tendon Injuries
- Arthritis
- Plica Syndrome
- Medial and Lateral Collateral Ligament Tears
- Cruciate Ligament Injuries
- Chondromalacia
- Osgood-Schlatter Disease
ACL injury. An anterior cruciate ligament or ACL injury is a tear of the anterior cruciate ligament (ACL), which is one of four ligaments that connect your shinbone to your thighbone. An ACL injury is particularly common in people who play basketball, soccer or other sports that require sudden changes in direction.
Posterior cruciate ligament (PCL) works as a counterpart to the anterior cruciate ligament (ACL). It connects the posterior intercondylar area of the tibia to the inner end of the femur. The function of the PCL is to prevent the femur from sliding off the anterior edge of the tibia and to prevent the tibia from displacing posterior to the femur.
The PCL and ACL are intracapsular ligaments because they lie deep within the knee joint. They are both not a part of the fluid-filled synovial cavity, with the synovial membrane wrapped around them. The PCL gets its name by attaching to the posterior portion of the tibia.
The PCL, ACL, MCL, and LCL are the four main ligaments of the knee in people.
Medial Collateral Ligament (MCL) Injury
The medial collateral ligament (MCL) is located on the inner aspect of the knee, but it’s outside the joint itself. Ligaments hold bones together to keep it stable and it adds strength to a joint. The MCL connects the top of the tibia, or shinbone, to the bottom of the femur.
An injury to the MCL is often called an MCL sprain. Ligament injuries can either stretch the ligament or tear it. MCL injury of the knee is usually caused by a direct blow to the knee, which is common in contact sports.
MCL injuries can be grades 1, 2, or 3:
- A grade 1 MCL injury is the least severe meaning that the ligament has been stretched but not torn.
- A grade 2 MCL injury means that your ligament has been partially torn, which may cause some instability in your knee joint.
- A grade 3 MCL injury is the most severe type of ligament injury and occurs when your ligament has been completely torn. Joint instability is common.
Lateral Collateral Ligament (LCL) Injury
The lateral collateral ligament (LCL) is the ligament that runs along the outside of the knee joint, from the outside of the bottom of the thighbone (femur) to the top of the lower-leg bone (fibula). The LCL helps keep the knee joint stable, especially the outer aspect of the joint.
An injury to the LCL could include straining, spraining, and partially or completely tearing any part of that ligament. The LCL is one of the more commonly injured ligaments in the knee.
What causes an LCL injury?
The main cause of LCL injuries is direct-force trauma to the inside of the knee.
Symptoms include:
- Swelling of the knee (especially the outer aspect)
- Stiffness of the knee joint that can cause locking of the knee
- Pain or soreness on the outside of the knee
- Instability of the knee joint (feeling like it’s going to give out)
Fractures. The bones of the knee, including the kneecap (patella), can be broken during motor vehicle collisions or falls. People whose bones have been weakened by osteoporosis can sometimes sustain a knee fracture simply by walking incorrectly.
Torn meniscus. The meniscus is formed of tough, rubbery cartilage and acts as a shock absorber between your shinbone and thighbone. It can be torn if you suddenly twist your knee while bearing weight on it.
Knee bursitis. Some knee injuries cause inflammation in the bursae, the small sacs of fluid that cushion the outside of your knee joint so that tendons and ligaments glide smoothly over the joint.
Patellar tendinitis. Tendinitis is irritation and inflammation of one or more tendons, which are thick, fibrous tissues that attach muscles to bones. The patellar tendon connects the thigh muscle on the front of the leg to the shinbone. Runners, skiers, cyclists, and those involved in jumping sports and activities may develop this condition.
Loose body. Sometimes injury or degeneration of bone or cartilage can cause a piece of bone or cartilage to break off and float in the joint space.
Iliotibial band syndrome. This occurs when the tough band of tissue that extends from the outside of your hip to the outside of your knee (iliotibial band) becomes so tight that it rubs against the outer portion of your femur. Distance runners and cyclists are especially susceptible to iliotibial band syndrome.
Dislocated kneecap. This occurs when the triangular bone (patella) that covers the front of your knee slips out of place, usually to the outside of your knee.
Hip or foot pain. If you have hip or foot pain, you may change the way you walk to spare these painful joints. But this altered gait can place more stress on your knee joint.