Summarize:

Kneecap fractures are common knee problems. You can fracture your knee just by falling onto your knee hard enough. If you fracture your knee, you may need surgery. Knee fractures are generally serious and take a long time to heal. If you have a fractured knee, you will feel pain in the front of the knee. The front of your knee will usually be swollen, and bruising may also occur. You will not be able to straighten the knee or walk and put pressure on the knee. Ligaments are the tissue that surrounds the joint and connects bones to other bones. People who play sports often injure their ligaments. Torn or stretched ligaments limit the movement of the knee, making it difficult to turn or twist, and your knee may also buckle or give way. Multiple ligaments may be injured at the same time. A stretched ligament is considered a sprain. With a sprain, the knee may swell or bruise, and the knee hurts and is hard to use. If the ligament has torn, there might be bleeding beneath the skin. Sometimes there is no pain because the tear also tears the pain receptors. Typically nerve damage will only occur when a ligament is completely torn. The anterior cruciate ligament (ACL) and the posterior cruciate ligament (PCL) are in the front and back of the knee, respectively. The ACL is responsible for forward movement and the PCL is responsible for backward movement. The ACL is usually injured during a sudden change of direction, and PCL injuries often occur during a direct impact to the front of the knee, such as in a motor vehicle accident. Sports such as soccer, football, basketball, and skiing lead to ACL and PCL injuries. The medial collateral ligament (MCL) provides stability of the inside of the knee. The lateral collateral ligament (LCL) provides stability of the outside of the knee. These are not as commonly injured as the other ligaments. These generally are injured when you get hit in the knee during sports. The meniscus are two pieces of cartilage in the knee that helps absorb impact from the thigh and shin. Knee cartilage injuries are one of the most common knee injuries. Though anyone can tear their cartilage, it is common among athletes. Older people tear their meniscus due to degeneration and thinning of the cartilage. A torn meniscus feels like a pop. You may not feel anything until a few days after the tear. Immediately, or up to a few days after the tear, you may experience pain, swelling, stiffness, difficulty walking, locking of your knee, your knee being weak and not holding, and a limited range of motion. A patella dislocation is when the kneecap is forced out of its normal position. You will see an obvious dislocation of the knee, where the knee looks like it is not in the correct place. The kneecap may pop back into place, though still cause problems. You will feel pain as soon as the patella pops out of place. Your knee will swell at the site. You also may not be able to move the knee or leg, and the area around the dislocation may be bruised. This knee injury is rare. It generally occurs due to major trauma, such as car crashes or a high speed injury. You may also dislocate your knee while doing certain physical activities, such as dance. Young people are at a higher risk for kneecap dislocation.
Decide if you have a fracture. Determine if you have a ligament injury. Check for a meniscus injury. Identify a dislocation.