Patellofemoral Instability Causes, Symptoms & Treatment

Overview

Your kneecap, or patella, connects muscles in your thigh (femur) to your shinbone (tibia). When your knee bends, it slides along a groove (femoral groove) at the end of your thigh bone. Patellofemoral Instability is a condition that occurs when the kneecap comes out of its groove. 

When this happens, it can result in pain, difficulty walking, and other problems. When the unstable kneecap comes out of the groove a little, but not completely, it is called subluxated. When it moves completely out of the groove, it is dislocated.

What causes Patellofemoral Instability?

Patellofemoral instability happens when the kneecap (patella) moves out of its normal position in the groove at the front of the knee. This may be caused by natural differences in knee anatomy, such as loose ligaments or a shallow groove, or by sudden twisting or pivoting movements that force the kneecap to slip or dislocate

• How the Injury Occurs: The injury occurs when sudden twisting, overextension, or direct trauma forces the patella out of its normal alignment, stretching or tearing stabilizing ligaments.
• Common Everyday Causes: Daily activities like climbing stairs, squatting, or tripping can also stress the kneecap and increase the risk of instability in susceptible individuals.

Patellofemoral instability is common in these sports:

• Football: Quick pivots and sudden directional changes can displace the kneecap.
• Gymnastics: High-impact landings and twisting movements place stress on the knee joint.
• Wrestling: Sudden movements and joint pressure increase the risk of dislocation.
• Basketball: Jumping, cutting, and rapid turns can lead to kneecap instability.
• Ice Hockey: Twists, stops, and collisions put repeated stress on the knee.
• Soccer: Pivoting, sudden stops, and directional changes can cause the patella to slip.
• Volleyball: Jumping and landing movements strain the knee and surrounding ligaments.

Symptoms

Patellofemoral instability occurs when the kneecap is not properly aligned in its groove, causing the knee to feel loose or unstable. The kneecap may slip, grind, catch, or pop, and in severe cases, fully dislocate, causing pain, swelling, and difficulty bending the knee. Common symptoms include:

• Knee giving out and unable to support weight: The knee may suddenly buckle or fail during activity.
• Kneecap slips off to the side: Visible displacement may occur during movement or dislocation.
• Knee catches during movement: The joint may lock or feel stuck temporarily.
• Pain in the front of the knee that increases with activity: Discomfort worsens with running, jumping, or sports.
• Pain when sitting or going up/down stairs: Prolonged bending or repetitive motion aggravates symptoms.
• Stiffness: Reduced flexibility and difficulty bending the knee.
• Creaking or cracking sounds during movement: Audible popping or grinding indicates improper tracking.
• Swelling: Inflammation around the kneecap may be present after activity or dislocation

Non-operative treatment

Often, the kneecap goes back into place on its own. However, if you have an initial kneecap dislocation episode and your kneecap is out of place, you should be seen in the emergency room, where the doctor gently pushes the kneecap back into place. If you have an episode where your kneecap dislocates completely after initial treatment, you should schedule an appointment to be seen by your doctor.

You may also want to see your orthopedic specialist if conservative treatment does not relieve your feelings that your kneecap is out of place or if you have persistent pain in your knee after a subluxation or dislocation episode.

Your doctor may ask you questions about your activity, perform a thorough physical examination, and conduct an apprehension test, which involves carefully moving the area around your patella as you extend your knee. If your kneecap is partially out of place, you are likely to experience a feeling that your kneecap is about to dislocate while the doctor performs this test. This helps to confirm the diagnosis of patella instability.

Your doctor may ask you questions about your activity, perform a thorough physical examination, and conduct an apprehension test, which involves carefully moving the area around your patella as you extend your knee. If your kneecap is partially out of place, you are likely to experience a feeling that your knee feels unstable and is about to dislocate while the doctor performs this test. 

Try these exercises to help address your condition:

Below is a PDF of the Exercise Program

Patellofemoral Instability

Surgical Treatment

If an unstable kneecap persists, surgery may be recommended to correct the knee after multiple dislocations. Surgery can also be an effective means of addressing damage to the underside of the kneecap and the end of the thigh bone caused by subluxations or dislocations of the patella. The exact surgical procedure varies greatly for this condition based on the degree of kneecap damage and the degree of improper tracking of the kneecap.

Common surgical procedures may include tightening or reconstructing the ligaments that stabilize the kneecap, repositioning the tendon that guides kneecap movement, or correcting bone alignment to improve tracking. The exact surgical approach depends on the underlying cause of instability, the degree of cartilage damage, and how the kneecap moves within the groove.