Overview
Patellar instability means the kneecap (patella) moves out of its normal groove in the thigh bone (femur). This can happen as a brief partial shift (subluxation) or a complete slip out of place (dislocation). When the patella is unstable, the tissues that guide it-especially the medial patellofemoral ligament (MPFL)-can be stretched or injured, which may lead to pain, swelling, and repeated episodes. Symptoms often worsen with activities that bend the knee and place load on the kneecap, such as stairs, squatting, jumping, or quick changes in direction.
Symptoms
People with patellar instability may notice a feeling that the kneecap is slipping, shifting, or "giving way," sometimes with a painful catch or a brief period of instability. Pain is commonly felt around the front of the knee and may increase when going downstairs, rising from a chair, deep bending, or twisting. Some patients develop swelling after episodes, and repeated instability can lead to stiffness and difficulty trusting the knee during sports or everyday tasks. In recurrent cases, the patella may track poorly, creating grinding or clicking sensations.
Causes
Patellar instability is usually caused by a combination of alignment and soft-tissue control issues that make it easier for the kneecap to move laterally. After an initial injury or episode, the MPFL and other stabilizing structures can become stretched, injured, or less effective, increasing the chance of recurrence. Biomechanics also plays a role, such as weaker hip and thigh muscles, poor movement control, and excessive knee valgus during activity. Less commonly, abnormal bone shape (such as trochlear groove dysplasia) can contribute to poor patellar tracking.
Risk Factors
Risk is higher in people with naturally looser joints or underlying connective tissue differences that affect ligament stability. Teenagers and young adults-especially those who participate in sports involving jumping, landing, or cutting-are at greater risk due to higher activity demands and growth-related changes. Malalignment patterns, such as excessive kneecap tracking outward or increased femoral/tibial angles, can increase instability. Prior kneecap dislocation or subluxation is a major risk factor for future episodes because stabilizing tissues may be damaged.
Prevention
You can reduce the risk of recurrence by focusing on physical therapy that improves hip strength, thigh muscle control, and neuromuscular coordination during bending and landing. Maintaining healthy body weight and choosing activities with gradual progression can lessen kneecap overload. Flexibility work for the hips and legs, along with good movement mechanics for squats, stairs, and sports, can help the patella track more reliably. Using an appropriate brace or taping during higher-risk activities may provide added guidance while you rebuild strength and control.
How the Diagnosis Is Evaluated
Clinicians typically start with a history of how the episode happened, what the kneecap did (slipped vs fully dislocated), and whether it has recurred. A physical exam often includes checking patellar tracking, range of motion, ligament laxity, and performing a patellar apprehension or stability assessment to see how easily the patella shifts. Imaging may include X-rays to evaluate alignment and check for bone injury, and an MRI may be ordered to assess MPFL injury, cartilage damage, or structural contributors when episodes are recurrent or symptoms persist. Additional studies such as CT may be considered in complex recurrent cases, but not every patient needs advanced imaging.
Nonsurgical Treatment Options
Non-surgical care usually focuses on reducing pain, restoring normal knee mechanics, and improving stability. Physical therapy is the cornerstone and often emphasizes strengthening the quadriceps with good control, especially alongside hip abductors/external rotators, plus balance and movement retraining for stairs, squatting, and sport-specific tasks. A knee brace, patellar tracking brace, or taping may help guide the kneecap during activity and decrease apprehension while you rehab. Anti-inflammatory pain relief such as NSAIDs, along with activity modification and icing after flare-ups, can help manage symptoms. For persistent pain or inflammation that limits rehabilitation, clinicians sometimes consider injections as an adjunct-such as corticosteroid injections for inflammatory flares, or biologic options like platelet-rich plasma (PRP)-and in selected cases hyaluronic acid injections may be discussed for associated cartilage-related discomfort.
When to Seek Medical Attention
Seek prompt medical attention if the kneecap appears fully dislocated, you cannot bear weight, or the knee looks deformed after an injury. Get urgent care if there is major swelling, fever, rapidly increasing pain, or a locked knee that cannot move normally. You should also be evaluated promptly if episodes keep recurring, if symptoms are worsening despite conservative care, or if numbness, significant weakness, or other neurologic symptoms occur. If the knee injury was followed by an inability to fully extend, severe instability, or a suspected fracture, medical assessment is important.
Frequently Asked Questions
It often feels like the kneecap is slipping, shifting, or "giving way," usually with pain in the front of the knee during bending, stairs, or twisting.
Rehab timelines vary, but meaningful improvements usually require weeks to months of consistent strengthening and movement retraining.
Next Steps
If you have episodes of kneecap slipping or repeated pain with stairs or squatting, consider an orthopedic or sports medicine evaluation to assess stability and tracking. Start or continue a structured physical therapy program focused on hip and thigh strength, movement control, and bracing strategies while you monitor symptoms. If you had a recent complete dislocation, swelling, or you cannot bear weight, get assessed promptly.