Patellar Instability: Symptoms, Causes, Treatment

What are the symptoms of patellar instability?

Patellar instability occurs when the kneecap (patella) moves out of its normal position, often due to a dislocation or subluxation (partial dislocation). This can cause a variety of symptoms, ranging from discomfort to more serious knee problems.

Symptoms of Patellar Instability:

• Kneecap slipping out of place: The most noticeable symptom is the sensation that the kneecap is moving out of its normal groove, often referred to as “giving way” or “slipping.” This may occur during activities like walking, running, or jumping.
• Pain in the front of the knee: Sudden or sharp pain in the front of the knee, especially when the patella dislocates or partially dislocates. The pain is often severe at the time of injury but may subside over time if the kneecap moves back into place.
• Swelling around the knee: Swelling can develop quickly after the patella moves out of position, especially after a complete dislocation. This swelling is caused by damage to the surrounding ligaments and tissues.
• Knee instability: The knee may feel unstable, especially during physical activities, leading to difficulty with movements like squatting, climbing stairs, or running.
• Limited range of motion: You may experience difficulty bending or straightening the knee fully due to pain or a feeling of the kneecap being out of place.
• Tenderness around the kneecap: The area around the patella may feel tender to the touch, particularly after a dislocation or subluxation.
• Popping or grinding sounds: Some people may hear or feel a popping sensation when the kneecap moves out of position or slides back into place.

Conclusion:

Patellar instability can lead to ongoing knee problems if left untreated, including chronic pain, recurrent dislocations, or damage to cartilage and ligaments. Treatment options range from bracing and physical therapy to surgical interventions, depending on the severity and recurrence of the instability.

What are the causes of patellar instability?

Patellar instability occurs when the kneecap (patella) moves out of its normal position, typically due to structural or mechanical issues in the knee. Several factors can contribute to patellar instability, leading to dislocation or subluxation (partial dislocation) of the patella.

Causes of Patellar Instability:

• Trauma or Injury: A direct blow to the knee or a sudden twisting movement can force the patella out of its normal groove, resulting in instability. This is common in sports or accidents where the knee is subject to impact or stress.
• Ligamentous Laxity: Some people have naturally loose ligaments, a condition called ligamentous laxity, which can make the patella more prone to moving out of place. This can be part of a broader condition like Ehlers-Danlos syndrome or joint hypermobility syndrome.
• Weakness in the Quadriceps Muscles: The quadriceps muscles help keep the patella in place. Weakness in these muscles, particularly the vastus medialis oblique (VMO), can allow the kneecap to drift out of position, especially during movement.
• Abnormal Patellar Tracking: In some individuals, the patella doesn’t move properly within the femoral groove (the groove in the thigh bone where the kneecap rests). Misalignment can occur due to muscle imbalances or abnormalities in the structure of the bones.
• Shallow Trochlear Groove: Some people are born with a shallow or poorly formed trochlear groove in the femur. This groove is meant to guide the patella, and if it is shallow, the patella may dislocate or subluxate more easily.
• Tight or Imbalanced Soft Tissues: Tight or imbalanced ligaments, tendons, or muscles around the knee can pull the patella out of alignment. For example, tight lateral structures can pull the kneecap toward the outside of the knee.
• Congenital Abnormalities: Some people are born with a predisposition to patellar instability due to congenital factors like misalignment of the legs (genu valgum or “knock knees”) or an unusually high-riding kneecap (patella alta).
• Previous Patellar Dislocation: After the patella dislocates once, the ligaments that stabilize it can become stretched or damaged, increasing the likelihood of recurrent dislocations or instability.
• Overuse: Repetitive stress on the knee from activities such as running or jumping can weaken the surrounding structures, leading to patellar instability over time.

Conclusion:

Patellar instability can be caused by a variety of factors, including trauma, muscle imbalances, structural abnormalities, and previous injuries. Identifying the underlying cause is crucial for proper treatment, which may involve physical therapy, bracing, or in some cases, surgery to stabilize the patella.

How is the diagnosis of patellar instability made?

The diagnosis of patellar instability is made through a combination of medical history, physical examination, and imaging tests. This process helps identify the extent of the instability and the underlying causes.

Diagnosis of Patellar Instability:

• Medical History:
• The doctor will ask about any history of knee injuries, dislocations, or subluxations.
• They will also inquire about symptoms like knee pain, swelling, or a feeling of the knee “giving way.”
• Details about the type of activities that trigger the instability, such as running, jumping, or twisting movements, are important.
• Physical Examination:
• The doctor will assess the knee for signs of instability, tenderness, swelling, and abnormal patellar movement.
• They may perform specific tests such as:
  • Patellar apprehension test: The doctor will gently push the kneecap laterally (to the outside) to see if it causes discomfort or a feeling of the kneecap wanting to slip out, which can indicate instability.
  • Quadriceps contraction test: The patient is asked to contract the quadriceps muscles while the doctor observes the movement of the kneecap to check for abnormal tracking.
• The doctor will also check the strength and flexibility of the quadriceps muscles and other structures around the knee.
• Imaging Tests:
• X-rays: X-rays are used to get a clear view of the bones in the knee. They help identify abnormalities such as a shallow trochlear groove, patella alta (high-riding patella), or any fractures caused by dislocation.
• Magnetic Resonance Imaging (MRI): An MRI provides detailed images of the soft tissues in the knee, such as ligaments, tendons, and cartilage. This helps assess any damage to the ligaments (such as the medial patellofemoral ligament), cartilage wear, or tears.
• CT Scan: In some cases, a CT scan may be ordered to better assess bone alignment and the structure of the patella and femoral groove.
• Gait and Functional Tests:
• The doctor may observe how the patient walks, squats, or climbs stairs to see if the patella moves abnormally during these activities.

Conclusion:

The diagnosis of patellar instability involves gathering a thorough medical history, conducting a physical examination, and utilizing imaging techniques like X-rays and MRIs to assess the knee’s structure. This helps determine the severity of the instability and guide appropriate treatment.

What is the treatment for patellar instability?

Treatment for patellar instability depends on the severity of the condition, the underlying cause, and whether the instability is chronic or due to a single traumatic event. The goal of treatment is to stabilize the patella, reduce pain, and improve knee function. Treatment options can be non-surgical or surgical.

Non-Surgical Treatments:

For mild cases or first-time dislocations, non-surgical treatment is often recommended.

• Rest and Activity Modification:
• Avoiding activities that aggravate symptoms (e.g., running, jumping, or twisting movements) to allow healing.
• Reducing weight-bearing on the affected leg can help prevent further stress on the knee.
• Bracing or Taping:
• A patellar stabilizing brace or taping can be used to hold the kneecap in its proper position during movement, especially during physical activities.
• These devices help reduce the risk of further dislocations or subluxations.
• Physical Therapy:
• Strengthening exercises focus on the quadriceps, particularly the vastus medialis obliquus (VMO), which helps stabilize the patella.
• Stretching tight structures, such as the iliotibial band (IT band) and lateral retinaculum, to correct patellar tracking.
• Balance and proprioception exercises to improve overall knee stability.
• Gradual return to sports or activities is important after therapy.
• Anti-inflammatory Medications:
• Over-the-counter nonsteroidal anti-inflammatory drugs (NSAIDs) like ibuprofen or naproxen can help reduce pain and inflammation.
• Ice and Elevation:
• Applying ice to the knee for 15–20 minutes at a time and elevating the leg can help reduce swelling and pain, especially after activity.

Surgical Treatments:

Surgery may be necessary for chronic instability, repeated dislocations, or when non-surgical treatments fail to stabilize the knee.

• Lateral Release:
• In this procedure, tight tissues on the outer (lateral) side of the knee are cut to allow the patella to move more freely and realign properly.
• Medial Patellofemoral Ligament (MPFL) Reconstruction:
• The MPFL is often damaged during a dislocation, leading to instability. In this surgery, the ligament is reconstructed using a graft (usually from a hamstring tendon) to stabilize the kneecap.
• Tibial Tubercle Transfer (Osteotomy):
• In cases where the patella is abnormally positioned (such as patella alta), the tibial tubercle (the bump on the tibia where the patellar tendon attaches) is moved to a better position. This procedure helps correct the patella’s alignment.
• Trochleoplasty:
• For individuals with a shallow trochlear groove, this surgery deepens the groove to better hold the patella in place and reduce the likelihood of dislocations.

Recovery and Rehabilitation:

• Post-surgical rehabilitation typically includes physical therapy to regain strength, flexibility, and proper patellar tracking.
• Full recovery can take several months, depending on the type of surgery and the severity of the instability.

Conclusion:

Treatment for patellar instability ranges from non-surgical options like physical therapy, bracing, and activity modification to surgical interventions for chronic or severe cases. The choice of treatment depends on the patient’s condition, goals, and severity of instability.