The patella, or kneecap, is a flat, triangular bone located at the front of the knee joint. Embedded within the quadriceps tendon, the patella acts as a pulley, significantly increasing the leverage of the quadriceps muscle to extend or straighten the leg. A patella fracture is a serious injury that breaks this bone and can compromise the knee’s entire extensor mechanism. Because the kneecap is essential for movement, a fracture severely limits the ability to stand or walk, requiring precise diagnosis and treatment to restore function.
Initial Assessment and Fracture Classification
Initial assessment of a suspected patella fracture involves a physical examination and detailed history. Patients typically present with significant pain, swelling, and bruising around the knee. A key sign of a compromised extensor mechanism is the inability to perform a straight leg raise against gravity.
Diagnosis is confirmed using plain X-rays, which allow the physician to assess the fracture pattern and the degree of displacement. For complex cases, such as those involving many fragments or significant joint surface damage, a Computed Tomography (CT) scan may be necessary to understand the fracture’s complexity and articular alignment.
Fractures are categorized based on the pattern of the break and displacement. A fracture is stable or non-displaced if fragments remain in contact and the extensor mechanism is intact, allowing the leg to be straightened. Displaced fractures involve separation of bone fragments, often defined by a gap exceeding 1 to 4 millimeters or a step-off in the joint surface of more than 2 to 3 millimeters. Common patterns include transverse, vertical, and comminuted (shattered) fractures.
Non-Surgical Management of Patella Fractures
Non-surgical treatment is reserved for non-displaced or minimally displaced fractures where the knee’s stability and extensor mechanism are maintained. This approach typically requires a fracture gap of less than 4 millimeters and minimal step-off in the joint surface. Crucially, the patient must be able to actively perform a straight leg raise, confirming the quadriceps-patella unit is functioning.
The cornerstone of non-operative treatment is joint immobilization using a cast or a specialized knee brace that holds the leg in full extension. Immobilization prevents movement at the fracture site that could lead to fragment separation and necessitate surgery.
Immobilization commonly lasts four to six weeks to allow initial healing. Patients are often allowed to bear weight on the injured leg while the brace is locked straight, relying on the intact extensor mechanism for stability. Follow-up X-rays monitor the fracture position. Once initial healing is confirmed, the device is replaced with a hinged brace to begin controlled, limited movement.
Surgical Repair Procedures
Surgery is required for patella fractures that are significantly displaced, involve a large step-off, or disrupt the knee’s extensor mechanism. The primary goals are to anatomically restore the smooth articular surface and re-establish the function of the quadriceps-patella complex. Accurate restoration minimizes the risk of developing post-traumatic arthritis.
The most common technique for simple transverse fractures is tension band wiring. This method uses Kirschner wires and a figure-of-eight wire loop. The tension band principle converts the quadriceps muscle’s pulling forces into compression forces at the fracture line, promoting stable healing.
For fractures involving a large, non-reconstructable fragment, partial patellectomy may be performed. This removes the damaged piece and reattaches the patellar tendon to the remaining bone. In rare cases of severe comminution, a total patellectomy (complete removal of the kneecap) might be necessary as a salvage procedure, though this is avoided due to significant loss of quadriceps strength.
Vertical fractures may be treated with lag screws alone. After fixation, the surgeon checks the integrity of the extensor mechanism by assessing the knee’s range of motion. Patients should be aware that hardware removal may be necessary later due to irritation or pain.
Rehabilitation and Return to Function
Recovery centers on a structured rehabilitation program, whether the fracture was managed surgically or non-surgically. Physical therapy (PT) begins soon after immobilization or surgery to combat joint stiffness, a common complication. Early, gentle range of motion (ROM) exercises are introduced to safely regain the ability to bend the knee.
The initial phase focuses on passive and active-assisted ROM, often restricted to a safe arc (e.g., 0 to 45 degrees of flexion) to protect the healing bone. Isometric exercises, such as quadriceps tightening sets, are started simultaneously to maintain muscle tone without moving the joint. ROM gradually increases, aiming for 90 degrees of flexion by six to eight weeks post-injury.
The subsequent phase emphasizes progressive strengthening of the surrounding muscles, targeting the quadriceps, hamstrings, and gluteals to restore functional power. Closed-chain exercises, such as squats and leg press, are introduced, along with balance and stability training.
Adherence to the PT regimen is essential for a good outcome, as early mobilization prevents long-term joint stiffness. While timelines vary, light daily activities often resume around three months. High-impact sports typically resume between three to six months, contingent upon achieving near-full ROM and at least 80% strength compared to the uninjured side.