What are acute kneecap (kneecap) injuries?


Acute kneecap (kneecap) injury can occur from a blow to the knee or a fall. Soft tissue damage, such as a ruptured patellar tendon or a broken bone, can occur.

Symptoms can include pain, swelling, a feeling of instability, or a blockage in the joint. Some types of injuries can be treated with strengthening exercises and rehabilitation, but others may require surgery.

Types of acute patellar injury

The patella is part of the knee joint along with the tibia (lower leg) and femur (femur). It is wrapped in the patellar tendon, which connects the quadriceps femoris muscle with the tibia below the knee joint.

Located in the front of the knee joint, the patella runs in the groove at the end of the femur (patellofemoral joint) and improves knee extension.

The most common types of acute patellar injury are as follows.

  • Patellar tendon tear: The tear can be small, partial, or complete. A complete rupture can be a serious injury that often requires surgery and repair for at least four to six months .
  • Dislocated kneecap : This occurs when the kneecap extends completely out of the groove of the thigh, usually to the side. Usually it needs to be put back in place, which is called repositioning. While it is painful, it is not as serious as a dislocated knee , in which the femur and shin lose contact with each other.
  • Patellar subluxation (unstable patella) : This condition is associated with a dislocated patella and refers to the patella that does not remain in the groove of the femur. It can involve a partial or complete dislocation and can cause pain and discomfort with physical activity.
  • Fracture (kneecap fracture) : The kneecap bone can break if it is dropped or bumped. It can be a complex fracture that requires surgery .
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Acute kneecap injuries cause symptoms common to other soft tissue and bone injuries, such as pain, swelling, and deformity. You will also often have functional symptoms.

Common symptoms include the following .

  • Pain – Most acute patellar injuries are very painful. Knee pain may be more noticeable with certain activities, such as climbing stairs (especially going downhill) or kneeling . But it can be so serious that you can't put weight on your leg.
  • Tumor : Acute injuries often cause swelling due to inflammation.
  • Noises: You may hear a popping or popping sound during an injury, especially if the patellar tendon is torn or dislocated. In some cases, you may hear a grinding or grinding noise ( crackling ), although this can also occur in normal knees.
  • Instability : After an injury, you will not be able to support your weight on your leg. It may bend when trying to stand or walk .
  • Locked joint : You may find that the joint is locked and you cannot bend or straighten your knee.
  • Deformity – Especially with a fracture or dislocation, the knee joint may appear deformed.
  • Contusion : There may be significant contusion from a fractured or ruptured tendon, or any injury to the kneecap.

Patellar injuries generally result in difficulty moving the knee, walking, or running. The patella is functionally important because it increases the stress on the knee joint and the force of the leg extension.

A dislocated kneecap can spontaneously return to its place. This can cause bruising and soft tissue damage. You should see your doctor as soon as possible for further testing, even if there is no damage.

Prepatellar bursitis (inflammation and swelling of the sac around the knee) can be a complication of traumatic injuries to the patella caused by the injury itself or by an infection resulting from the injury. In addition to the swelling in the front of the kneecap, this area can be painful and hot. If the bursitis is caused by an infection, there may also be a fever and chills.


Acute kneecap injuries can result from injuries, sports, or anatomical problems in the knee joint.

Accidents and injuries

The location of the kneecap at the front of the knee makes it vulnerable to fractures, dislocations, or tendon ruptures during falls, impacts to the knee, or sudden impacts such as the dashboard in a car accident.

Traffic accidents represent 78.3% of patellar fractures. Industrial and domestic accidents represent 13.7% and 11.4%, respectively .

If a person has osteoporosis , weak bones can increase the risk of a patellar fracture from a slight fall or blow to the knee. Pathological fractures of the patella can also occur in the case of a bone infection or a bone tumor.

Sports injuries

Acute kneecap injuries can also occur during violent movements, such as those that can be performed during sports, such as when the foot is supported and the torso rotates rapidly while swinging a baseball bat .

You can also tear your patellar tendon when landing in a jump with your knee bent and your foot in place. You may be predisposed to a patellar tendon tear if you already have patellar tendonitis (jumper's knee) , which is inflammation caused by overuse of the knee joint. This is seen in people who jump on hard surfaces, such as basketball or volleyball players.

A sudden contraction of the quadriceps muscle can lead to a kneecap fracture. This can happen when jumping from a height, although this rarely happens.

Anatomical differences

Changes in the anatomy of the knee can contribute to the risk of injury, especially when it comes to instability or dislocation.

Some people are born with a shallow or irregular femoral groove. This compromises the stability of the patellofemoral joint and can lead to displacement of the patella due to seemingly normal activities, not just a blow or fall.

Some people may be more prone to dislocation of the kneecap due to weakening of the ligaments. Patella luxations are more common in teenage girls.


Depending on your circumstances, you can see your primary care provider or seek emergency care. An urgent evaluation is best if the knee injury occurred in a fall or accident, or if the dislocation of the patella has not returned.

Your healthcare professional will take your history and tell you what caused your knee pain, your symptoms at the time (such as a clapping sound), and your current symptoms.


During a physical exam, your doctor will determine if you can walk, bend, or extend your knee. They will palpate the knee for areas that show defects, displacement, or local pain. Visual inspection of the knee can determine if there is obvious swelling, deformity, or displacement.

Manual tests and maneuvers are used to assess damage to the patella or tendons, including attempts to extend the knee against gravity. A leg stretch test can detect abnormalities in the extensor mechanism, which includes the quadriceps tendon, patella, and patellar tendon.

Images and labs

X-rays are often the first imaging method because they can show if there is a fracture that is important to detect or rule out early.

This may be a single image, or a doctor may order an MRI to further evaluate damage to ligaments, tendons, or cartilage.

Blood tests are not usually done for knee injuries, but they can be done specifically to look for signs of inflammation if an infection is suspected. If there is significant swelling, in some cases arthrocentesis may be done to remove fluid from the knee and analyze it in a laboratory for infection or blood from the injury.

The differential diagnosis may include arthritis and chondromalacia patella (runner's knee). They can be a source of knee pain without injury or be present in addition to other injuries to the kneecap.

Watch out

Treatment of these various acute conditions of the patella depends on the diagnosis. However, there are some general guidelines to follow. Your healthcare professional will advise you based on your diagnosis.

Home remedies

Acute kneecap injuries require self-care that you can do until you get medical attention and then, as recommended by your healthcare provider:

  • Rest the injured knee to prevent further damage and allow time for the swelling to subside.
  • Apply ice to your knee to reduce swelling. To avoid skin injury, make sure there is a tissue barrier between the ice pack and the skin, and avoid applying ice to the injury for more than 15 minutes at a time.
  • Take steroidal anti- inflammatory drugs (NSAIDs) such as Advil (ibuprofen) and Aleve (naproxen) to reduce inflammation and relieve some of the pain.


Patella luxation (a procedure in which the patella returns to the femoral groove) should be reduced. If this does not happen spontaneously, the doctor will perform the reduction as soon as possible.

Pain relievers may be needed to reduce the size so that the doctor can straighten the leg and manipulate the kneecap. Often it will snap back into place with slight pressure as your leg is extended.


Any acute injury to the kneecap may require immobilization with a cast, splint, or brace to allow the bone, tendon, or other soft tissue to heal. Your healthcare provider will recommend an appropriate option, if available.

Your healthcare professional may recommend that you do not lean on the affected leg while immobilizing it. You may need to use crutches or other mobility aids until the end of this period.

Surgical procedures

A fractured kneecap may require surgery if parts of the bone are out of place. This often means placing wires, screws, plates, or dowels to connect the pieces of the bone and hold them in place during healing.

Complete patellar tendon tears often require surgery. Sutures are placed over the tendon and attached to surgical anchors or holes in the patella. This can be done on an outpatient basis.

There are several surgical procedures to stabilize the patella that can be performed for recurrent patellar dislocations or subluxations. Recurrent partial and complete dislocations are associated with damage to the medial patellofemoral ligament, which holds the patella in place. Surgery can be done to repair or rebuild a ligament .


For any acute patellar injury, physical therapy will likely be recommended after the initial swelling has subsided and immobilization is no longer necessary. Immobilization itself leads to stiffness and loss of muscle strength. Your physical therapist will restore range of motion and muscle strength to your knee .

If weight bearing has been prohibited, you will gradually learn to keep weight on your injured leg. This begins with resting the toes for several weeks, then moves to 50% load, and finally after four to six weeks, depending on the type of injury, to full load .

Knee function requires balancing the strength of the knee muscles. The most important thing is to keep the quad and hamstring groups flexible and balanced. Your physical therapist will recommend specific exercises based on your condition.

Get the word of drug information

Acute kneecap injury is often not only painful, but also unpleasant, as it will mean restrictions on your activities during recovery. Talk to your doctor and physical therapist to understand what you can do to make a full recovery. Most people can often return to their previous activities after treating a fracture, tendon tear, or dislocation.

Frequently asked questions

  • The most important sign may be severe symptoms such as pain in or around the knee, swelling, inability to walk, instability, and difficulty moving the knee. Any of these symptoms requires a visit to a doctor for a damage evaluation.

  • Recovery time depends on the type of knee injury. For example, recovery from a patella fracture generally takes three to six months, while a tendon rupture requires a four to six month recovery period. A dislocated knee requires only four to six weeks of recovery.

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