Partial Dislocation of the Knee: Understanding Subluxation, Causes, Symptoms, and Treatment

What is a partial dislocation of the knee?

A partial dislocation of the knee, also known as a subluxation, occurs when the bones forming the knee joint temporarily lose their normal alignment but spontaneously or manually return to their correct position without requiring a full, external reduction.

Understanding Knee Anatomy

To comprehend a partial dislocation, it's essential to understand the basic anatomy of the knee. The knee is a complex hinge joint formed by three bones: the femur (thigh bone), tibia (shin bone), and patella (kneecap). These bones are held together and stabilized by a network of ligaments (e.g., anterior cruciate ligament - ACL, posterior cruciate ligament - PCL, medial collateral ligament - MCL, lateral collateral ligament - LCL), which are strong, fibrous tissues. The joint surfaces are covered with articular cartilage, and two C-shaped cartilaginous discs called menisci act as shock absorbers and help distribute weight.

What is a Partial Dislocation (Subluxation)?

A partial dislocation (subluxation) differs from a full dislocation in that the joint surfaces temporarily separate but then spontaneously or easily realign. In a full dislocation, the joint surfaces remain completely separated until manually reduced. While a partial dislocation may seem less severe, it can still cause significant pain, instability, and potential damage to surrounding structures.

There are two primary types of knee subluxation:

• Patellar Subluxation: This is the most common form of knee subluxation. It occurs when the patella (kneecap) temporarily slides out of its trochlear groove (the groove at the end of the femur where the patella normally tracks) and then quickly returns to its place. This usually happens laterally (towards the outside of the knee).
• Tibiofemoral Subluxation: This is much less common and typically more severe. It involves the temporary misalignment of the tibia relative to the femur. This type of subluxation often indicates significant ligamentous injury and may be associated with high-energy trauma.

Causes and Risk Factors

Partial dislocations of the knee can result from a combination of traumatic events and underlying anatomical or biomechanical predispositions.

• Traumatic Injuries:
  • Direct blow: A direct impact to the knee, especially from the side.
  • Twisting injury: Sudden change in direction while the foot is planted.
  • Hyperextension: Forcing the knee beyond its normal range of motion.
  • Awkward landing: After a jump, particularly in sports.
• Anatomical Predispositions (primarily for patellar subluxation):
  • Patella alta: A kneecap that sits too high in the trochlear groove.
  • Trochlear dysplasia: A shallow or poorly formed trochlear groove, allowing the patella to slide out more easily.
  • Ligamentous laxity: Naturally loose ligaments, making the joint less stable.
  • Muscle imbalances: Weakness in the vastus medialis obliquus (VMO) portion of the quadriceps, which helps stabilize the patella, or tightness in the lateral structures.
  • Increased Q-angle: A larger angle between the quadriceps muscle and the patellar tendon, often seen in individuals with wider hips, which can pull the patella laterally.
• Activities:
  • Sports involving jumping, pivoting, or sudden stops (e.g., basketball, soccer, gymnastics).
  • Repetitive stress or overuse in individuals with predisposing factors.

Signs and Symptoms

The symptoms of a partial knee dislocation can vary in intensity but typically include:

• Sudden, sharp pain: Often localized to the front or side of the knee.
• Feeling of "giving way" or "shifting": The sensation that the knee buckled or moved out of place.
• Temporary visible deformity: The kneecap may appear out of place momentarily before it reduces.
• Swelling: Rapid onset of swelling due to inflammation and bleeding within the joint.
• Tenderness: Pain upon touching the affected area.
• Limited range of motion: Difficulty bending or straightening the knee due to pain and swelling.
• Popping or clicking sensation: May be heard or felt at the time of injury.
• Apprehension: A feeling of fear or instability when attempting certain movements.

Diagnosis

Accurate diagnosis is crucial to determine the extent of the injury and guide appropriate treatment.

• Clinical Examination: A healthcare professional will take a detailed medical history and perform a physical examination. This includes assessing the knee's range of motion, palpating for tenderness, and performing stability tests (e.g., patellar apprehension test for patellar instability, Lachman test for ACL integrity).
• Imaging Studies:
  • X-rays: Used to rule out fractures and assess bone alignment, including the position of the patella and the depth of the trochlear groove.
  • Magnetic Resonance Imaging (MRI): Provides detailed images of soft tissues, including ligaments, menisci, and articular cartilage. An MRI can identify associated injuries often missed by X-rays.
  • Computed Tomography (CT) scan: May be used to further evaluate bony anatomy, such as trochlear dysplasia or patellar alignment, particularly in cases of recurrent instability.

Treatment and Management

Treatment for a partial knee dislocation depends on the type of subluxation, the severity of the injury, and whether it's a first-time occurrence or recurrent.

• Immediate Care (Acute Phase):
  • RICE protocol: Rest, Ice, Compression (with a bandage), and Elevation to reduce pain and swelling.
  • Immobilization: A knee brace or splint may be used temporarily to stabilize the joint and allow initial healing.
  • Pain management: Over-the-counter or prescription anti-inflammatory medications.
• Reduction: For a patellar subluxation, the kneecap often reduces spontaneously. If not, a healthcare professional can manually guide it back into place. Tibiofemoral subluxations typically require immediate medical intervention for reduction.
• Conservative Management: This is the most common approach, especially for first-time patellar subluxations without significant associated injuries.
  • Physical Therapy: A cornerstone of recovery. Focuses on strengthening the muscles around the knee and hip (quadriceps, hamstrings, glutes), improving proprioception (joint awareness), restoring range of motion, and correcting muscle imbalances.
  • Bracing: Functional braces may be recommended for activities to provide added stability and prevent recurrence.
• Surgical Intervention: Surgery may be considered for recurrent subluxations, significant ligamentous tears (e.g., medial patellofemoral ligament - MPFL), or specific anatomical abnormalities.
  • MPFL reconstruction: Rebuilding the primary ligament that stabilizes the patella laterally.
  • Tibial tubercle osteotomy: Repositioning the bony attachment of the patellar tendon to improve patellar tracking.
  • Trochleoplasty: Deepening the trochlear groove to provide better patellar stability.
  • Ligament repair/reconstruction: For tibiofemoral subluxations involving major knee ligaments.

Rehabilitation and Recovery

Rehabilitation is a critical component of recovery, whether treatment is conservative or surgical. It follows a phased approach:

• Phase 1: Acute Management: Focus on controlling pain and swelling, protecting the joint, and restoring initial range of motion.
• Phase 2: Restoring Strength and Function: Gradually increasing strengthening exercises for the quadriceps, hamstrings, glutes, and core. Incorporating balance and proprioceptive training.
• Phase 3: Return to Activity/Sport: Progressing to sport-specific drills, agility training, and plyometrics, with a gradual return to full activity under guidance.

The duration of recovery varies widely depending on the severity of the injury, the type of treatment, and individual factors, ranging from several weeks to many months.

Prevention Strategies

While not all knee injuries are preventable, certain strategies can significantly reduce the risk of partial dislocations:

• Strength Training: Develop balanced strength in the quadriceps, hamstrings, and gluteal muscles. Pay particular attention to the vastus medialis obliquus (VMO) for patellar stability.
• Flexibility and Mobility: Maintain good flexibility in the hamstrings, quadriceps, and hip flexors to prevent muscle imbalances and improve joint mechanics.
• Proprioceptive Training: Incorporate balance exercises (e.g., single-leg stands, wobble board) to improve joint awareness and reactive stability.
• Proper Technique: Learn and use correct form for sports-specific movements, jumping, and landing to minimize stress on the knee.
• Appropriate Footwear: Wear supportive shoes that fit well and are appropriate for your activity.
• Bracing: Individuals with a history of knee instability or certain anatomical predispositions may benefit from prophylactic bracing during high-risk activities, as recommended by a healthcare professional.

When to Seek Medical Attention

If you experience symptoms consistent with a partial knee dislocation, it is crucial to seek prompt medical attention. A healthcare professional can accurately diagnose the injury, rule out more severe damage, and recommend the most appropriate course of treatment to ensure proper healing and prevent long-term complications.