The patella, or kneecap, is a bone that slides within a groove on the thigh bone, called the trochlea, when the leg bends and straightens. A patellar dislocation occurs when this bone completely shifts out of that normal groove, most frequently to the outside of the knee. This acute injury often results from a sudden twisting motion or a direct blow to the knee. Recognizing the signs of this injury is important because a dislocation can damage the surrounding ligaments and cartilage, necessitating immediate medical attention.
Visual and Sensory Indicators of Dislocation
The visible deformity of the knee joint is the primary sign of a patellar dislocation. The kneecap will appear obviously misplaced and typically sits on the outer side of the knee, creating an abnormal bulge. The front of the knee may look flattened, and the medial femoral condyle might appear prominent.
At the moment of injury, a person often experiences a sudden, severe, sharp pain, frequently accompanied by a distinct popping or grinding sensation. This feeling results from the patella forcefully moving out of its track and often tearing supporting structures, such as the Medial Patellofemoral Ligament (MPFL). The injured leg will usually be locked in a partially bent position, and the person will be unable to straighten it.
The ability to bear weight or even move the leg is immediately compromised, leaving the joint feeling unstable or “giving way.” Following the initial trauma, rapid and localized swelling develops as blood fills the joint capsule (hemarthrosis) due to soft tissue damage. Bruising around the medial side of the knee is also a common indicator, signifying the tearing of the medial restraints.
Immediate Steps Following Injury
Once a patellar dislocation is suspected, contact emergency medical services or seek immediate transport to a hospital. This injury should not be treated at home, even if the kneecap spontaneously moves back into place. Professional assessment is necessary to check for associated injuries like fractures or significant ligament tears.
While waiting for medical help, the injured leg must be carefully stabilized and protected from any movement. Use pillows, towels, or rolled-up clothing to support the knee in its current position. This stabilization helps prevent further trauma to the joint until trained personnel can take over.
Applying a cold pack to the swollen area can help manage pain and reduce swelling. The ice should be wrapped in a damp towel and never placed directly onto the skin. Never attempt to push or force the kneecap back into its groove, as this risks severe damage to the joint cartilage and ligaments.
Medical Procedures and Recovery
Upon arrival at a medical facility, diagnosis is confirmed through a physical examination and imaging studies. X-rays confirm the patella’s position and rule out associated fractures or bony fragments. A Magnetic Resonance Imaging (MRI) scan may also be performed to assess the extent of soft tissue damage, particularly to the MPFL and the articular cartilage.
The primary acute treatment is closed reduction, where a medical professional gently manipulates the patella back into its trochlear groove. This is often performed after the patient receives pain medication or a mild sedative to relax the surrounding muscles. The technique involves flexing the hip and gently guiding the patella while slowly extending the knee.
Following a successful reduction, the knee is typically immobilized using a brace or splint for a short period, often up to a few weeks, to allow the torn soft tissues to begin healing. Physical therapy starts promptly, focusing on static exercises to strengthen the quadriceps muscle, which is important for patellar tracking. Full recovery for a first-time, uncomplicated dislocation typically takes six to eight weeks before returning to normal daily activities.