The largest joint in your body, your knee is also one of the most complex. Due to its complicated structure, it's one of the most susceptible joints to injury and the degenerative effects of aging. Orthopedic surgeons at HonorHealth treat all types of knee injuries and conditions, from fractures and dislocations, to sprains and ligament tears.
How the knee works
The knee is made up of bones, ligaments, cartilage and tendons that all serve specific functions:
Bones: The knee is the connecting point for three bones:
- Thighbone (femur).
- Shinbone (tibia).
- Kneecap (patella).
Ligaments: The three bones of the knee are connected and held together by four main ligaments that help keep the knee stable. These include:
- Collateral ligaments: Two collateral ligaments in the knee control sideways movement:
- Medial collateral ligament (MCL) on the inside of the knee.
- Lateral collateral ligament (LCL) on the outside of the knee.
- Cruciate ligaments: Located inside the knee joint, they control back-and-forth motion:
- Anterior cruciate ligament in the front of the knee joint.
- Posterior cruciate ligament at the back of the knee joint.
Articular cartilage: The knee bones move and glide smoothly across one another when you bend or straighten your leg with the help of articular cartilage. It's a substance that covers the area where the thighbone, shinbone and the back of the patella meet.
Meniscus: The knee has two thick, rubbery C-shaped segments of meniscal cartilage. They rest between the thighbone and shinbone to lubricate the joint and offer cushion and stability while acting as shock absorbers.
Tendons: They connect the muscles to the bones.
- Quadriceps tendon: It connects front thigh muscles to the patella.
- Patellar tendon: It connects the patella and shinbone.
Called compartments, three sections of the knee can become injured or diseased:
- Medial compartment, the inner part of the knee.
- Lateral compartment, the outer part of the knee.
- Patellofemoral compartment, the part of the knee that's located behind the kneecap.
Common knee injuries
Due to its many structures and compartments, the knee can sometimes be damaged. Knee injuries often involve more than one structure or part of the knee.
Some of the most common knee injuries include:
- Fractures: Fractures, or breaks in the bone, can happen to any of the bones that form the knee, or to multiple bones of the knee at one time. Knee fractures often are caused by a traumatic injury such as a fall, vehicle accident or a high-impact sports injury.
- Dislocation: This occurs when the knee bones move or are forced out of alignment. This can be due to a structural defect in the knee that enables the bones to move out of place or a traumatic injury like a fall, vehicle accident or high-impact sports injury.
- Anterior cruciate ligament (ACL) injuries: ACL injuries are most often associated with sports such as football, soccer and basketball that require you to make sudden movements or changes in direction. Most ACL injuries also include damage to other parts or ligaments in the knee.
- Posterior cruciate ligament injuries: These are most often caused by some sort of trauma to the front of the knee when it's bent, like landing hard on the knee during a fall, a vehicle collision or a sports accident. Many posterior cruciate ligament injuries are classified as partial tears and can heal on their own with proper care and support.
- Collateral ligament injuries: These most often are associated with contact sports like football where a collision pushes the knee sideways. Medial collateral ligament tears are the most common types of collateral ligament injuries, and they usually result from a direct hit or blow to the outside of the knee.
- Meniscal tears: Most commonly associated with high-intensity sports that require sudden movements like twisting, cutting or pivoting, meniscal tears also can develop as a result of arthritis or general weakening of the cartilage that comes with age.
- Tendon tears: The tendons in your knee can become stretched or torn from an awkward landing, a fall or a direct hit to the front of the knee. Tendon tears occur most often in middle-aged individuals who run or play sports that require a lot of jumping.
Signs of injury
Signs that you should see a knee specialist include:
- Severe pain in your knee, including inner knee pain and outer knee pain.
- Inability to move your knee.
- Inability to walk without limping.
- Severe swelling at the injury site.
- Grinding, snapping or clicking noises with movement.
- A popping sound or feeling your knee give when the injury occurs.
Knee pain causes
There are many possible causes of acute and chronic knee pain, stiffness and instability, including soft tissue injuries, arthritis and general wear and tear. Orthopedic specialists treat all types of knee injuries and conditions that may be caused by or are related to:
- Arthritis. Cartilage lets the bones in the knee move smoothly across one another. The degenerative effects of arthritis can break down that cartilage, causing progressive pain, discomfort and even loss of motion.
- Bursitis (inflammation around the joint).
- Tendonitis (inflammation of the tendons).
- Fractures or dislocations.
- Sprains/soft-tissue tears.
Diagnosing knee pain
Finding the right treatment for your injury or condition starts with an accurate diagnosis. Your knee specialist may use a variety of medical imaging technologies and in-office exams to identify the exact location and cause of your knee pain or other symptoms.
Medical imaging procedures that may be used to evaluate and diagnose your knee injury include:
- CT scans.