Overview
The patella, commonly known as the kneecap, is a flat, triangular bone located at the front of the knee joint. It sits within a specialized groove at the end of the thigh bone, where it is held in place by a complex network of ligaments and muscles. The primary function of the patella is to provide leverage for the quadriceps muscles as they straighten the leg.
Patella dislocation occurs when the kneecap slips completely out of its normal position within this groove. This is part of a spectrum known as patellofemoral instability, which also includes subluxation, where the kneecap partially slides out of place before returning to its original position.
These injuries are most frequently observed in adolescents and young, active individuals. While a single episode can cause significant discomfort, repeated occurrences can lead to long-term joint issues if the underlying instability is not addressed.
Causes and Risk Factors
Patella dislocation typically results from a combination of mechanical forces and individual anatomical predispositions.
Common Mechanisms of Injury The most frequent cause is a non-contact twisting injury to the knee while the foot is firmly planted on the ground. This sudden change in direction puts immense stress on the stabilizers of the kneecap. In other instances, a direct blow to the knee can knock the patella out of its joint. These movements are common in sports such as badminton, tennis, soccer, and basketball.
Anatomical Contributors Certain physical factors can make an individual more susceptible to instability:
- Trochlear Dysplasia: A condition where the groove in the thigh bone is too shallow or flat to secure the patella properly.
- Patella Alta: A high-riding kneecap that sits further above the joint than usual.
- Ligamentous Laxity: Generally loose ligaments throughout the body can reduce the stability of the knee joint.
- Muscle Imbalance: Weakness in the inner quadriceps muscle, known as the vastus medialis oblique, prevents the patella from being pulled into the correct alignment during movement.
- Alignment Issues: Factors such as flat feet or an increased angle between the hip and the knee can alter the tracking of the kneecap.
Symptoms
When a patella dislocates, the symptoms are usually immediate and severe, often causing a temporary inability to walk.
Acute Symptoms
- Visible Deformity: The knee may appear misshapen, with the kneecap appearing as a lump stuck to the outside of the knee.
- Inability to Straighten: The knee is often stuck in a bent position and cannot be fully extended.
- Rapid Swelling: Bleeding into the joint space, known as haemarthrosis, often causes the knee to swell quickly following the injury.
- Severe Pain: Intense pain is typically felt along the inner region of the kneecap.
Chronic Symptoms In cases of ongoing instability, patients may experience a persistent sensation that the knee is about to “give way” or feel unstable during activity. There may also be tenderness along the poles of the patella and a sense of apprehension when performing certain movements.
Diagnosis
A thorough assessment by a healthcare professional is necessary to confirm the dislocation and evaluate for associated damage to the bone and cartilage.
Physical Examination The professional will review the history of the injury and conduct a focused knee examination. This includes palpating the joint for tenderness and performing stability tests, such as the apprehension test, where the patella is gently moved to check for signs of guarding or discomfort.
Diagnostic Imaging
- X-rays: These are used to confirm the position of the patella and identify any fractures or loose bone fragments within the joint.
- Magnetic Resonance Imaging (MRI): This provides a detailed view of soft tissues, allowing the professional to check for tears in the medial patellofemoral ligament (MPFL) and assess the health of the joint cartilage.
- Computed Tomography (CT): This may be used to measure bone alignment and the tracking patterns of the kneecap to help plan for long-term management.
Treatment Options
Treatment plans are tailored to the individual based on the severity of the injury and whether it is a first-time or recurrent event.
Acute Management and Self-Care If the patella does not relocate spontaneously, a doctor must manually move it back into place. Immediate care typically follows the RICE (Rest, Ice, Compression, and Elevation) method to manage pain and reduce swelling. In some cases, a specialist may need to remove excess fluid or blood from the joint.
Non-Surgical Categories
- Immobilisation: The knee is often placed in a brace or splint for a period of time to allow the injured ligaments to heal.
- Physiotherapy: This is the mainstay of treatment for most patients. Rehabilitation focuses on strengthening the quadriceps, hip stabilizers, and core muscles to improve the tracking of the kneecap.
- Activity Modification: Patients are advised to avoid high-risk activities until they have regained sufficient strength and stability.
- Medication: Oral anti-inflammatory medicines are frequently used to manage symptoms during the recovery process.
Surgical Treatment Surgery is generally considered if there is evidence of a fracture, a loose piece of bone or cartilage in the joint, or if the patient suffers from chronic instability despite rehabilitation.
Common surgical procedures include:
- MPFL Reconstruction: Rebuilding the primary ligament that prevents the kneecap from sliding outward.
- Lateral Release: Loosening tight tissues on the outside of the knee that may be pulling the patella out of alignment.
- Tibial Tuberosity Transfer: A bony realignment procedure where the attachment point of the patellar tendon is moved to improve tracking.
- Trochleoplasty: Deepening the groove in the thigh bone for patients with severe anatomical variations.
Prevention and Lifestyle Management
Managing patella health involves maintaining the strength and flexibility of the lower limbs to reduce the risk of future injury.
Exercise and Strengthening Regular engagement in a structured exercise programme is vital. Focusing on the medial quadriceps and hip external rotators helps provide dynamic support to the kneecap.
Practical Daily Considerations
- Proper Technique: Using correct form during sports and avoiding sudden, uncoordinated lateral movements can help prevent stress on the joint.
- Supportive Gear: Wearing a patellar stabilizing sleeve or brace during high-impact activities may provide additional security for those with known instability.
- Weight Management: Maintaining a healthy body weight reduces the overall load placed on the knee joints during daily movement.
When to Seek Medical Attention
Prompt evaluation is necessary if a knee injury occurs that results in the kneecap moving out of place. You should also seek medical attention if you experience:
- Symptoms following a traumatic injury or direct blow to the knee.
- Persistent or worsening knee pain that does not respond to rest.
- A recurring feeling of the knee giving way or “popping”.
- New symptoms of weakness, numbness, or loss of function in the leg.
If symptoms persist or worsen, it is advisable to consult a qualified healthcare professional for proper evaluation.
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Disclaimer: This page is for general educational purposes only and should not be considered medical advice. Please consult a qualified healthcare professional for personalised assessment and treatment.
