What is an unstable kneecap?
The kneecap, or patella, is critical to stability in the knee joint. The kneecap is a small bone located in the front of the knee joint where the thighbone and shinbone meet. It acts as a shield for the joint and connects the muscles in the front of your upper leg to your shinbone. The underside of the kneecap is covered with slippery hyaline cartilage that allows the bones in the joint to glide smoothly as your leg moves.
Because the kneecap connects thigh muscles to the bone in your lower leg, bending and straightening your leg causes the kneecap to be pulled up or down. The kneecap is held in place by a groove in the thighbone. However, if the groove is uneven or too shallow, the kneecap may slide out of place causing partial or complete dislocation. A blow to the kneecap could also pop it out of position in the joint.
Once a kneecap has dislocated, the knee is at greater risk of:
- Future dislocations
- Permanent cartilage damage
- Osteoarthritis
What are the symptoms of an unstable kneecap?
Symptoms of an unstable kneecap include:
- A sense that the knee is buckling and can no longer support your weight
- The kneecap slips off to the side of the joint and no longer feels as though it is in the proper position
- A catching sensation in the knee joint when you bend or straighten your leg
- Pain in the front of your knee that increases with activity
- Knee pain while sitting
- Stiffness or swelling in the knee
- Creaking or cracking sounds when you move your knee
How is an unstable kneecap diagnosed?
Your doctor will diagnose an unstable kneecap based on:
- Your medical history, including whether you have ever dislocated your knee
- Your symptoms (such as the location of the pain)
- The activities that make the pain better or worse
- A physical examination of the movements and strength of your knee
Your doctor may also order diagnostic imaging, including an X-ray or MRI, to confirm the diagnosis.
How is an unstable kneecap treated nonsurgically?
Nonsurgical treatment options for a first knee dislocation or unstable kneecap include:
- Reduction to return the knee to its proper position (in the case of dislocation)
- A knee brace
- Physical therapy
- Rest
What are the surgical treatment options for an unstable kneecap?
If the kneecap instability becomes chronic, or if you dislocate your knee more than once, you and your doctor may consider surgery to stabilize the kneecap. Surgical options include:
MPFL reconstruction surgery
This is the most common surgery used to address an unstable kneecap.
- The physician takes one of the patient’s hamstrings, or a hamstring from a cadaver
- Then, the physician makes a new ligament to replace the damaged medial patellofemoral ligament, or MPFL, that holds the kneecap in place
- This is outpatient surgery that can be performed in about an hour
Tibial tubercle osteotomy
In cases where the patient’s kneecap and shinbone aren’t well aligned, this surgery is used to reposition the bones in the knee joint, thereby stabilizing it.
- In this procedure, the physician cuts a piece of bone from the shin
- Then, the physician shifts the alignment of the kneecap so that the bones are correctly positioned
- This is also performed as an outpatient surgery
How long does it take to recover from kneecap stabilization surgery?
Each kneecap stabilization surgery requires a six- to eight-month recovery period. The patient is on crutches for six weeks and then works with a Summit physical therapist to regain motion and rebuild strength.
Additional resources for you
- More on Summit’s Sports Medicine services
- From American Academy of Orthopedic Surgeons (trusted external resource): Unstable Kneecap
