How does the patella break?
The patella is located directly under the skin and is not protected by muscles, so when you fall on a bent knee, it takes the blow. The second mechanism is indirect: the quadriceps muscle contracts sharply, keeping the body from falling, and tears the bone across. A mixed mechanism is also possible. The direction of traction of the muscle and the patellar ligament itself determines whether the fragments will separate: if the lateral supporting structures are intact, there may be no displacement; if they are torn, the fragments will separate and the extensor apparatus stops working.
- Transverse fracture is the most common option
- Comminuted fracture due to a strong direct blow
- Longitudinal fracture without loss of extension function
- Avulsion of the inferior pole of the patella
- Non-displaced fracture with intact lateral structures
- Fracture with displacement and loss of extension
Symptoms
The pain is localized exactly in the area of the kneecap and sharply intensifies when trying to straighten the leg. The knee quickly swells: blood from the broken bone enters the joint cavity, and within an hour or two the joint becomes tight and hot. A painful gap may be felt above the patella, and it itself feels divided into parts. The key test is an attempt to raise the straightened leg while lying down: if the extensor apparatus is torn, this is impossible. Walking is extremely difficult, the leg gives way.
- Pain in the kneecap area
- Rapid swelling of the joint due to blood accumulation
- Inability to raise a straight leg
- Palpable gap between fragments
- Bruising on the front of the knee
- Unsteadiness when trying to walk
Diagnostics
X-ray of the knee joint in direct and lateral projections reveals the fracture line and the degree of divergence of fragments; the side shot is the most informative. Additionally, axial alignment is performed to see longitudinal fractures and evaluate the articular surface. It is important not to confuse a fracture with a congenital feature - a bilobed patella, when the bone consists of two fragments with smooth rounded edges, often on both sides and without trauma. For comminuted fractures, CT is used to plan surgery, and ultrasound and MRI help evaluate the quadriceps tendon and patellar ligament.
- X-ray of the knee in frontal and lateral projections
- Axial placement of the patella
- CT scan for comminuted and intra-articular fractures
- Ultrasound of the extensor apparatus tendons
- MRI for suspected ligament and cartilage damage
- Active leg extension test
Treatment
If the fragments have not separated and the person can maintain a straight leg, treatment is conservative: the knee is fixed with an orthosis or splint in the extension position for 4–6 weeks, walking with support is allowed, and isometric exercises for the quadriceps muscle are prescribed. If the fragments diverge by more than a few millimeters, the articular surface is damaged, or there is loss of extension, an operation is performed: the fragments are brought together and fixed with knitting needles with a wire loop, screws, or combined structures. Small fragments of the lower pole are sometimes removed to restore the ligament. Complete removal of the patella is extremely rare.
- Orthosis or splint in extension for 4–6 weeks
- Walking with support and dosed load
- Isometric exercises for thigh muscles
- Osteosynthesis with knitting needles and a wire loop
- Fixation with screws for suitable fracture geometry
- Joint puncture for tense hemarthrosis
Rehabilitation and possible consequences
The main goals of recovery are to restore full extension and strength of the quadriceps muscle and gradually restore flexion. They start with tension of the muscle in the brace and movements in the ankle, then add passive and active flexion of the knee in the range allowed by the doctor. The thigh muscle loses volume very quickly, so exercise is important from the first days. Possible consequences are stiffness, weakness of extension, pain under the kneecap during exercise, and the development of arthrosis of the patella, especially if the articular surface is not accurately restored. Metal structures are often removed after fusion due to discomfort under the skin.
- Early quadriceps tension
- Gradual increase in knee flexion angle
- Walking with support until muscle control is restored
- Knee Strength and Stability Exercises
- Control images before confirmation of fusion
- Removal of metal structures if they are disturbed