September 14, 2015
The knee is a complex structure and one of the most stressed joints in the body. It is the largest joint, vital for movement, and vulnerable to injury.
The knee is the most commonly injured joint by adolescent athletes with an estimated 2.5 million sports-related injuries annually.
Many knee injuries can be successfully treated with simple measures, such as bracing and strengthening exercises. Other injuries may require surgery to correct.
Although not all knee injuries can be prevented, education on knee anatomy, how injuries happen, and how best to care for them when they do, can help prevent potential complications or long-term disability from common knee injuries.
Contents of this article:
You will also see introductions at the end of some sections to any recent developments that have been covered by MNT's news stories. Also look out for links to information about related conditions.
Fast facts on knee injuries
Here are some key points about knee injuries. More detail and supporting information is in the main article.
- An estimated 6,664,324 knee injuries were presented to emergency departments from 1999 through 2008, equaling 2.29 knee injuries per 1,000 individuals.
- Those 15 to 24 years of age had the highest injury rate.
- Participation in sports and recreational activities are risk factors for knee injury.
- Stairs, ramps, landings, and floors are most associated with knee injuries sustained outside of sports.
- As life expectancy increases, the incidence of knee injuries among older adults can also be expected to increase.
- Knee injuries account for 60% of high school sports-related surgeries, and occur among both sexes and across all age groups.
- The point at which two or more bones are connected is called a joint.
- The cruciate ligaments are named such as they form a cross in the middle of the knee.
- Female athletes participating in basketball and soccer are two to eight times more likely to suffer an anterior cruciate ligament (ACL) injury compared to male athletes.
- Athletes who have suffered an ACL injury are at increased risk of developing arthritis later on in life.
- A direct blow to the knee is a serious injury and requires immediate medical attention.
- A history of locking episodes suggests a tear in the meniscus.
The knee is a hinge joint that is responsible for weight bearing and movement. It consists of bones, meniscus, ligaments, and tendons.
The femur (thigh bone), tibia (leg bone), and patella (knee cap), make up the bones of the knee.
Meniscus is sometimes called cartilage, and the knee has two; the medial (inner) and lateral (outer). These crescent-shaped discs act as a cushion, or "shock absorber" so that the bones of the knee can move through their range of motion without rubbing against each other.
Ligaments act like strong ropes to connect bones to other bones. The knee has four; ACL (anterior cruciate ligament), MCL (medial collateral ligament), PCL (posterior cruciate ligament), and LCL (lateral collateral ligament).
These tough bands of tissue connect muscles to bone and provide stability to the joint.
Although they are not technically part of the knee joint, the equally important hamstrings and quadriceps are the muscles that strengthen the leg and help flex the knee.
Common knee injuries
Knees are most often injured during sports activities, exercising, or as a result of a fall. Pain and swelling, difficulty with weight bearing, and instability are the most common symptoms experienced with a knee injury.
Sprains and strains
Sprains and strains are injuries to the ligaments. The ACL is the ligament most often injured.
These injuries usually happen in sports such as soccer, football, and basketball where the knee might experience a sudden twisting motion, a rapid change in direction, or an incorrect landing from a jump.
Often a pop or a snap is heard followed by swelling. Symptoms also include tenderness along the joint line and pain with walking.
A meniscal tear generally happens during sports where the knee twists, pivots, or an individual is tackled.
Even normal wear from aging can weaken the meniscus, causing it to tear with a simple awkward turn during normal day to day activities. Symptoms of a tear are usually pain, stiffness, swelling, locking, and decreased range of motion.
A fracture is most often caused by trauma, such as falls, motor vehicle accidents, and sports-related contact. The most common bone broken around the knee is the patella.
The most common overuse injury is "runner's knee," or patellofemoral pain syndrome (PFPS). Runner's knee is a painful condition that is common in runners and cyclists.
Pain is experienced behind or around the kneecap, and can travel to the thigh or shin. The pain worsens with activity and is relieved by rest.
Treatments and rehabilitation for knee injuries
All knee injuries should be evaluated by a medical provider in a timely manner.
In order to correctly diagnose the type of injury, the provider needs an accurate description of the circumstances involved:
- What was the specific activity at the time of injury?
- Was the knee weight bearing at the time?
- Was there an external force?
- Was there pain?
- What was the position of the knee?
- Was there a pop, tear, or snap?
- Does the knee seem unstable?
- Was there immediate or delayed swelling?
- Is there ability to bear weight?
- Is there a history of previous injury to the knee?
Basic treatment for common knee injuries includes rest, ice, elevation, and an over the counter pain reliever such as Ibuprofen.
It is also important to begin strengthening and stretching exercises 24-48 hours after minor injuries, or as advised by a medical practitioner. There should be a gradual return to normal activities. In some cases, such as an ACL tear, arthroscopic surgery is necessary to repair the damage.
Additionally, short-term immobilization and no weight bearing may be necessary for proper healing. Crutches may be recommended for a limited time to prevent additional injury.
Physical therapy is often indicated to assist a person's recovery to pain-free range of motion. An important extension of therapy involves continuing a home exercise program. Without adequate rehabilitation, a person will tend to have ongoing problems with an injured knee. The goal of treatment is to restore stability, strength and mobility.
Prevention of knee injuries
The following tips may help prevent common knee injuries:
- Warm up by walking and stretching gently before and after playing sports
- Keep the leg muscles strong by using stairs, riding a stationary bicycle, or working out with weights
- Avoid sudden changes in the intensity of exercise
- Replace worn out shoes. Choose ones that fit properly and provide good traction
- Maintain a healthy weight to avoid added pressure on the knees
- Always wear a seatbelt
- Use knee guards in sports where knees could get injured.
The knee is a complex weight-bearing joint that is essential for mobility, and prone to injury. The most common knee injuries include sprains, strains, tears, overuse, and fractures.
Maintaining strong, flexible leg muscles and seeking prompt medical attention for all knee injuries is essential to assure accurate diagnosis and appropriate treatment of the injury. Additionally, keeping the supporting leg muscles strong, and practicing injury prevention will help keep the knee healthy across the lifespan.
Written by Kathleen Davis FNP