A torn patellar tendon is a rupture or tear of the fibrous tissue connecting the kneecap to the shin bone. This injury represents a significant disruption to the knee’s extensor mechanism.
The Patellar Tendon’s Role
The patellar tendon is a strong band of tissue at the front of the knee, extending from the bottom of the kneecap (patella) to the top of the shinbone (tibia). It functions as a continuation of the quadriceps tendon.
This tendon works with the quadriceps muscles to facilitate knee extension. It transmits the force from the thigh muscles, enabling movements like straightening the leg. The patellar tendon also helps maintain kneecap alignment.
Common Causes of Tears
Patellar tendon tears result from a strong force applied to the knee. Sudden, forceful quadriceps contractions, often during jumping or landing, are common causes. Direct impact to the front of the knee, such as from a fall, can also lead to this injury. The greatest stress on the patellar tendon occurs when the knee is flexed beyond 60 degrees.
Pre-existing conditions can weaken the tendon, making it prone to tearing. Patellar tendinitis, or “jumper’s knee,” is an inflammation that can weaken the tissue. Chronic medical conditions like diabetes, rheumatoid arthritis, lupus, and chronic renal disease also increase risk. Prolonged corticosteroid use or previous knee surgery can further increase susceptibility.
Identifying a Patellar Tendon Tear
A patellar tendon tear often causes a sudden popping or tearing sensation at the moment of injury. This is followed by immediate, sharp pain below the kneecap. Swelling and bruising around the front of the knee are common symptoms.
A noticeable indentation or gap may be felt or seen above the kneecap where the tendon has torn. With a complete tear, the kneecap may shift upward into the thigh, no longer anchored to the shinbone.
The ability to straighten the leg is significantly impaired or lost. Bearing weight on the affected leg may be difficult or impossible, and the knee might buckle. Even small tears can make walking and daily activities challenging.
Tears are categorized as partial or complete. In a partial tear, some tendon fibers remain intact, meaning the kneecap and shinbone are still partially connected. Partial tears cause pain, swelling, and limited motion, but some knee function may remain. A complete tear means the tendon has fully separated from the kneecap, leading to a total loss of the ability to straighten the knee.
Medical Confirmation and Initial Steps
A healthcare professional diagnoses a patellar tendon tear through medical history and physical examination. The exam checks for tenderness, swelling, and a palpable gap in the tendon. A key assessment is the knee extension test, which evaluates the ability to actively straighten the leg. Loss of this function is a primary indicator. Patella height changes are also inspected.
Imaging tests confirm the diagnosis and determine tear extent. X-rays can show if the kneecap has moved higher (patella alta), suggesting a tear, or if bone has broken off. Magnetic Resonance Imaging (MRI) visualizes soft tissues to confirm the tear, assess severity, and differentiate between partial and complete ruptures.
After diagnosis, initial steps protect the knee. Immobilization, often with a knee immobilizer or brace, keeps the knee straight to aid healing. Crutches are necessary to avoid putting full weight on the injured leg. Patients should elevate the knee to reduce swelling. Consultation with an orthopedic specialist follows to discuss treatment options.