A kneecap becomes dislocated when the patella bone, which sits at the front of the knee, comes out of position. In the process, the connective tissues that hold the bone in place may stretch and tear.
A dislocated kneecap is a common injury when a person changes direction suddenly with their feet planted on the ground — such as during sports or when dancing.
Research suggests that a first-time dislocation of the kneecap can take at least 6 weeks to heal. The time depends on the necessary treatment and any factors that suggest that the injury may reoccur. Some people also require extensive physical therapy.
Below, we explore the symptoms, treatment options, and recovery timeline for a dislocated kneecap. We also look into the risk factors for a recurrent injury.
The symptoms depend on the severity of the dislocation and whether there is damage to surrounding structures.
If the injury is less severe, the kneecap may only partially dislocate before returning to its original position. This is called a subluxation, and the person may be able to return to their regular activities fairly quickly.
Symptoms of a partial dislocation may include:
- the feeling that the kneecap has slipped to one side
- pain, especially at the front of the knee
- popping or crackling sounds in the knee
- stiffness and swelling
- a locking or catching sensation in the knee
- a feeling of instability
When the kneecap has fully dislocated, the person may:
- find that their knee has an odd, angular appearance
- have moderate to severe pain
- feel a strong popping sensation in their knee
- experience severe stiffness and swelling
- find that their knee locks, making it difficult or impossible to move the leg
- be unable to walk or stand
Anyone with symptoms of a partial or full dislocation should receive medical attention.
Even if the kneecap shifts back into place on its own, a doctor needs to ensure that the other structures in the knee are correctly aligned and undamaged. This requires an X-ray.
The right treatment for a dislocated knee depends on the type and severity of the injury and whether the bone, cartilage, and other surrounding tissues have been damaged.
If the injury is minor, the doctor may recommend ways to protect the knee as the body heals on its own with time.
Common nonsurgical options include:
- physical therapy
- RICE therapy, which involves:
- resting the knee to prevent further injury
- applying ice packs to reduce inflammation and pain
- using a compression bandage to ease swelling and provide support
- elevating the knee to reduce swelling
- nonsteroidal anti-inflammatory drugs, such as ibuprofen or aspirin, to reduce inflammation and pain
- crutches or a cane to take weight off the knee and aid mobility
- a brace to support the knee and stabilize the kneecap
- shoe inserts, called orthotics, to reduce stress on the knee
- aspiration, a simple clinical procedure to remove any excess fluid in the joint
It is uncommon to need surgery after a first-time dislocation of the kneecap, but surgery may be necessary if the injury is severe or there is a high risk of repeat dislocations.
Some surgical treatment options include:
This minimally invasive procedure involves inserting a camera and surgical tools through small incisions around the knee.
With their tools, the surgeon assesses the extent of the damage and may be able to perform repairs.
In people with more severe injuries or recurrent dislocations, reconstructive surgery can:
- repair damaged tendons or ligaments
- remove and repair damaged cartilage and bone
A 2015 review notes that surgeons most commonly perform reconstructive surgery to repair the medial patellofemoral ligament, which attaches the inside of the kneecap to the long bone of the thigh.
According to the review, a tear in this ligament occurs in as many as 90% of kneecap dislocations.
Tibial tuberosity transfer
This, the most involved and complex type of surgery for recurrent kneecap dislocations, involves cutting away a piece of the shin bone, or tibia, and moving it to a position that improves the stability and alignment of the kneecap.
The surgeon may then insert screws to help keep the transferred bone in place while it heals.
Anyone who has dislocated their kneecap is at risk of the injury happening again. According to a 2020 meta-analysis, people who have received nonsurgical treatment for a first-time kneecap dislocation experience a reoccurrence about 50% of the time.
The risk of a recurrent dislocation increases if the body has not had enough time to recover fully from the initial injury.
A 2018 review observes that surgical treatment may be a good option for people with a first-time dislocation who have a high risk of recurrence. However, it is important to keep in mind that surgery can also increase the risk of other knee issues, such as arthritis.
Regular strength training and physical therapy may help prevent reinjury, in some cases.
The amount of time that it takes to heal can depend on:
- the severity of the injury
- whether there is damage to surrounding structures in the knee
- whether the person underwent surgery
The first stage in recovery may involve the RICE approach, which includes:
- applying ice packs to the area
- using a compression bandage
- elevating the leg
The doctor may recommend a brief period of immobilization in a brace to allow the knee to rest and to prevent further injury. The researchers behind a 2014 study recommend immobilizing the knee for 2–3 weeks, but the right amount of time depends on the injury.
People often use crutches or a cane in the early stages of recovery to take weight off the knee.
Doctors also usually recommend physical therapy to help regain the range of motion and strengthen the muscles that support the knee. This also helps to reduce the likelihood of recurrent dislocation.
It may take about 6 weeks before the person can regain the full range of motion and walk without assistance. It usually takes longer for the person to return to athletic activity.
A person who has undergone surgery may take 6 months or longer to resume their regular sports or exercise routine.
The right approach to treatment and the timing of recovery varies, depending on severity of the dislocation.
A person who has experienced one kneecap dislocation has an increased risk of another. Even after making a full recovery, a person may need to continue to strengthen the muscles that surround the knee to help prevent a recurrent injury.
Having surgical treatment may reduce the risk of future dislocations, in some cases, but it carries other risks. Discuss all treatment options and their long-term effects with a doctor.
Working closely with a doctor and a physical therapist can help ensure a smooth recovery and minimize the chances of reinjury.