Patella/Kneecap Instability

Patellar instability, also known as patellar subluxation or dislocation, is a medical condition common in adolescents and adults. It is the abnormal movement of the patella (kneecap) out of its normal position within the joint. Patellar instability is common in females aged 10-16.

Common symptoms of patellar instability include:

• Pain and discomfort around the kneecap.
• A feeling of the knee “giving way.”
• Swelling and inflammation.
• Audible popping or snapping sensation during movement.
• Deformity or abnormal appearance of the knee.

Patellar instability can be caused by various factors, which can be broadly categorized into anatomical, traumatic, and functional causes.

Anatomical factors:

• Abnormal alignment of the legs can predispose to dislocation, typically with valgus (knocked knee) and rotational malalignment
• Trochlear dysplasia is a shallow or uneven groove in the femur that can make the patella unstable and more likely to dislocate.
• Patella alta is a condition in which the kneecap sits higher than normal in relation to the thigh bone, increasing the risk of instability.
• Ligament laxity is due to a connective tissue disease or due to dislocation of the patella, which stretches and strains the ligaments.
• An abnormally shaped patella.

Trauma such as a blow to the knee, a fall, or a collision can cause the patella to dislocate. Indirect trauma, such as a sudden twist or pivot from a sport, can lead to dislocation and is more commonly the cause of patellar dislocation.

Functional causes include muscle imbalances and poor biomechanics during running, jumping, or changing direction, which can increase the risk of dislocation.

Some medical conditions that affect muscle coordination and control can predispose to patellar instability.

Other risk factors include a family history of patellar dislocation and a prior dislocation, which increases the risk of patellar instability.

Diagnosing patellar instability typically involves reviewing your medical history and evaluating risk factors. Dr. Waterman will perform a thorough clinical examination, including assessing knee stability and range of motion. Imaging studies like X-rays, MRI, or CT scans may be ordered to visualize the structural aspects of the knee joint and identify any underlying issues.

The management of patellar instability depends on its severity and underlying causes. Treatment options may include:

Conservative management:

Primary patellar instability, or a first-time dislocation, can be treated with conservative measures unless a fracture, area of cartilage damage, or severe instability is present. These include:

• A structured physical therapy program, including strengthening exercises.
• Bracing and taping can offer added support and even correct patellar tracking.
• NSAIDs to treat pain and inflammation
• Activity modification

Surgery:

Surgical intervention may be necessary when conservative treatments fail to provide adequate relief or in cases of recurrent patellar instability. Options include:

• Medial Patellofemoral Ligament (MPFL) Reconstruction: A procedure that involves reconstructing the MPFL, which is often damaged during patellar dislocation.
• Lateral Retinacular Lengthening: In cases where tight lateral structures pull the patella out of alignment, a lateral lengthening procedure will allow the patella to sit properly and be more balanced in the trochlear groove.
• Tibial Tubercle Transfer (Osteotomy): A procedure that repositions the tibial tubercle (the bony prominence where the patellar tendon attaches) to correct patellar tracking issues. This can involve medialization and/or distalization to correct malalignment. 
• Trochleoplasty: A surgical procedure to deepen a shallow or misshaped trochlear groove, providing better containment for the patella.
• Patellar realignment surgeries: These aim to correct the patella’s alignment through various techniques, such as soft tissue balancing or bony realignment with a femoral or tibial osteotomy.
• Cartilage Restoration Procedures: In cases where patellar instability has led to significant cartilage damage, procedures such as chondroplasty, marrow stimulation, osteochondral autograft or allograft transplantation, or matrix-assisted autologous chondrocyte implantation may be performed to restore damaged cartilage.

Rehabilitation following surgery for patellar instability is crucial for optimal recovery. Successful treatment of patellar instability requires a tailored approach that addresses each patient’s specific needs and underlying causes. Early intervention and adherence to a comprehensive rehabilitation program are essential for achieving the best possible outcomes.