Patellar Dislocation and Kneecap Instability: Symptoms, Causes and Treatment
A patellar dislocation happens when the kneecap, or patella, slips fully out of the groove it normally glides in, usually shifting toward the outer side of the knee. It is often a sudden, painful event during a twist or a direct blow, and it can leave the knee feeling unstable afterward. After a first dislocation, the soft tissue that holds the kneecap in place can be stretched or torn, which can lead to patellar instability, a tendency for the kneecap to keep slipping out. The good news is that many people recover well, and there are effective ways to stabilize a kneecap that keeps dislocating.
If your kneecap has shifted out of place or feels like it might give way, it helps to understand what is going on. The board-certified and fellowship-trained knee and sports medicine specialists at Resurgens Orthopaedics diagnose and treat patellar dislocations and kneecap instability at locations across metro Atlanta.
Overview
- What Are Patellar Dislocation and Instability?
- What Causes a Patellar Dislocation?
- Patellar Dislocation and Instability Symptoms
- How Patellar Instability Is Diagnosed
- Patellar Dislocation and Instability Treatment
- Schedule an Appointment for Knee Care
What Are Patellar Dislocation and Instability?
The kneecap normally rides in the groove at the end of the thighbone where the kneecap moves, gliding up and down as you bend and straighten your knee. A patellar dislocation is when the kneecap comes all the way out of that groove. A partial dislocation (called a subluxation) is when the kneecap shifts out of place but not completely. Sometimes the kneecap pops back into place on its own when the leg straightens, and sometimes it needs to be guided back in.
Patellar instability is an ongoing condition that can follow. A key stabilizer, a ligament that helps keep the kneecap in place (called the MPFL), acts like a tether that keeps the kneecap from sliding too far to the outside. When it is stretched or torn during a dislocation, the kneecap has less to hold it in place, so it can dislocate again more easily. That recurring tendency is what is meant by patellar instability.
What Causes a Patellar Dislocation?
A patellar dislocation can come from an injury, an underlying anatomy that makes the kneecap less stable or a combination of the two. Common causes and risk factors include:
- Twisting or Impact: A non-contact twist or change of direction, common in sports, or a direct blow to the knee
- Shallow Groove: A shallow or flat groove at the end of the thighbone where the kneecap moves, which gives the kneecap less of a track to sit in
- High-Riding Kneecap: A kneecap that sits above the deepest part of the groove
- Loose Ligaments: Flexible ligaments throughout the body
- Leg Alignment: Knock-knees or differences in how the thighbone and shinbone are positioned
- Previous Dislocation: A prior patellar dislocation, since the kneecap dislocates again in 15% to 60% of cases after a first dislocation
A forceful contraction of the thigh muscles can also pull the kneecap out of its groove. Often, a mix of an injury and underlying anatomy is at work, which is why treatment looks at both.
Patellar Dislocation and Instability Symptoms
A full dislocation is usually obvious and painful, while instability can be more subtle. Common symptoms include:
- Visible Shift: The kneecap moves to the outer side of the knee at the moment of injury
- Sudden Pain: Severe knee pain when the kneecap slips out
- Swelling: Swelling soon after the injury
- Giving Way: A feeling that the knee is buckling or that the kneecap is shifting or catching
- Fear of Slipping: A feeling that the kneecap might slip out again when bending or turning
Please Note: If a kneecap is dislocated and does not go back into place on its own, it needs prompt medical care to be guided back safely. After any dislocation, having the knee evaluated by a specialist helps check for cartilage damage and guide a plan to help keep the kneecap stable.
How Patellar Instability Is Diagnosed
A knee specialist can usually diagnose a patellar dislocation or instability with a physical examination and your account of what happened. Your physician will check how the kneecap tracks and moves, test how far it shifts to the side and look for tenderness and swelling. Imaging fills in the detail. An X-ray shows the bones and the shape of the groove and can reveal a loose fragment, while an MRI can show the MPFL and the cartilage, which helps confirm the injury and guide treatment.
Patellar Dislocation and Instability Treatment
Treatment depends on whether this is a first dislocation or a recurring problem, and on what is making the kneecap unstable. A first-time dislocation is often treated without surgery, while a kneecap that keeps dislocating may need a procedure to stabilize it.
Nonsurgical Treatment
After the kneecap is back in place, first-line care is usually nonsurgical:
- Bracing: A brace or support to protect the knee and keep the kneecap aligned while it settles
- Activity Changes: A short break to let the swelling and soreness ease
- Physical Therapy: Strengthening the thigh and hip muscles that help control the kneecap, a key part of recovery
- Medication: Over-the-counter anti-inflammatory medication to ease pain and swelling
Surgical Treatment
When the kneecap keeps dislocating despite a fair trial of nonsurgical care, surgery can restore stability. The right procedure depends on what is driving the instability. A common option is MPFL reconstruction, which uses tendon tissue to rebuild the ligament. When the underlying problem is bony, such as alignment or the position where the kneecap tendon attaches, the surgeon may reshape or reposition bone to correct it, sometimes in combination with ligament repair. Your Resurgens surgeon will explain which approach fits your knee and your goals.
Schedule an Appointment for Knee Care
If your kneecap has dislocated or keeps feeling unstable, a knee specialist can find out why and help you get back to your activities with confidence. Book an appointment online today with Resurgens Orthopaedics or call us at (404) 847-9999.