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Knee

Patella Instability

What is the patella?

The patella, or kneecap, is a small, flat bone that sits in front of the knee joint. It glides within a groove in the femur (thigh bone) and helps transmit force from the quadriceps to extend the knee.

Patellar instability occurs when the kneecap moves out of its normal position, usually sliding laterally (to the outside). This can range from a partial shift (subluxation) to a full dislocation where the kneecap completely exits the groove.

Symptoms include knee pain, a sensation that the kneecap is “slipping” or “giving way,” swelling, and difficulty walking or straightening the leg. After a dislocation, the knee may feel unstable or untrustworthy, especially during activity.

Causes include trauma (like a direct blow or awkward twist), loose ligaments, shallow or misshaped femoral grooves, and high-riding kneecaps (patella alta). It can also result from muscle imbalance or abnormal alignment of the lower extremity.

Diagnosis begins with a physical exam and review of symptoms. Imaging, such as X-rays, helps assess alignment and rule out fractures. MRI is often used to evaluate damage to cartilage, ligaments (especially the medial patellofemoral ligament/MPFL), and to check for bone bruising or loose bodies.

Initial treatment includes rest, bracing, physical therapy, and strengthening. For patients with recurrent dislocations or significant structural abnormalities, surgery may be needed to restore stability. Common procedures include medial patellofemoral ligament (MPFL) reconstruction and tibial tubercle osteotomy.

The MPFL is a key ligament that helps keep the kneecap in place. MPFL reconstruction involves replacing this ligament with a graft to stabilize the patella and prevent future dislocations. It is often performed through small incisions.

A tibial tubercle osteotomy procedure involves shifting the bony attachment of the patellar tendon (tibial tubercle) to improve kneecap tracking and alignment. The bone is repositioned and secured with screws, usually in combination with other procedures like MPFL reconstruction.

Recovery typically takes 4 to 6 months. A brace and crutches are used early on, followed by physical therapy to restore motion and strength. Most patients return to full activity, including sports, around 5 to 6 months post-op.

Recovery takes about 5 to 6 months, but bone healing requires more protection early on. Weight-bearing is limited for the first few weeks. Physical therapy begins gradually, and return to higher-level activities is usually allowed around 6 months, depending on healing.

At a Glance

Sachin Allahabadi, MD

  • Board-Certified & Fellowship-Trained Sports Medicine Surgeon
  • Expertise in Minimally Invasive Knee & Shoulder Surgeries
  • Assistant Professor of Clinical Orthopaedic Surgery, Houston Methodist Hospital & Weill Cornell Medical College
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