Patellofemoral pain syndrome

Causes of pain syndrome

Patellofemoral articulation pathology rarely occurs in isolation. The syndrome is based on several biomechanical and structural disorders:

• Patellar fractures. If a stepped deformity of the articular surface persists after trauma (even with tight apposition and bone healing), this inevitably provokes the progression of post-traumatic patellofemoral arthrosis, persistent pain syndrome, and limited mobility.
• Chronic posterior cruciate ligament (PCL) insufficiency. Unlike anterior cruciate ligament (ACL) injuries where the main complaint is instability, patients with chronic PCL damage complain specifically of anterior knee pain. This is due to the fact that to stabilize the joint, the person constantly overstrains the quadriceps femoris muscle. The increased load on the patella causes articular cartilage degeneration.
• Pyrophosphate arthropathy. This disease has a pronounced predisposition to affect the patellofemoral compartment. Radiographs reveal joint space narrowing, meniscal chondrocalcinosis, and characteristic remodeling of the distal femoral metaphysis.

Diagnosis of patellar injuries

In the first episode of patellar dislocation or acute trauma, a comprehensive approach is necessary, as no single imaging method has absolute accuracy. It is important to remember that transchondral lesions in the acute period can often be detected only via arthroscopy.

1. Radiography. The baseline method for ruling out osteochondral fractures and intra-articular bodies. Anteroposterior and lateral views are mandatory for everyone. An axial view (20° flexion) or Merchant view (45° flexion) are performed additionally, but in acute dislocation, they are often omitted due to severe pain.
2. MRI. Indicated to assess soft tissues. It allows visualization of medial patellofemoral ligament (MPFL) tears, cartilage damage of the lateral femoral condyle, and the medial head of the quadriceps.
3. CT. Used primarily for precise preoperative planning.
4. Joint puncture. Serves a dual purpose. Fluid removal reduces pain, and the presence of blood (hemarthrosis) is a reliable sign of a clinically significant injury.

Principles of patellar fracture management

At the prehospital stage, care consists of applying a transport splint with the knee in extension, mandatory foot immobilization, and referral to a trauma hospital. Subsequent tactics depend on the degree of extensor mechanism damage and fragment displacement.

Conservative treatment Used for longitudinal, transverse, or comminuted fractures without articular surface deformation and with a fragment diastasis of no more than 2–3 mm.

• A puncture is performed to remove hemarthrosis and administer 20 ml of a 2% procaine solution for analgesia.
• A plaster cast or brace is applied from the gluteal fold to the ankle for 1 month (knee flexed at 5°).
• Rehabilitation starts early: isometric thigh muscle contractions are allowed on day 3, and crutch walking on days 4–5. Ability to work is restored in 6–8 weeks.

Surgical treatment An absolute indication is damage to the supportive ligaments (diastasis greater than 3–5 mm). Surgery is performed on an emergency basis.

• Method of choice: tension-band wiring (Weber technique using Kirschner wires and a cerclage wire loop). Its main advantage is the ability to initiate joint motion within a few days.
• Alternatives: modified purse-string lavsan sutures are used for multifragmentary fractures, but require external immobilization for 6 weeks.
• Important rule: regardless of the surgical technique, including patellar fragment resection, the supportive tendoligamentous apparatus must be repaired.

Class and exam questions

What else to study on this topic

• Physical tests for anterior cruciate ligament injury (Lachman test, anterior drawer test, pivot shift test).
• Causes of false-negative results in knee ligament testing.
• Calcium hydroxyapatite crystal deposition disease and the pathogenesis of Milwaukee shoulder syndrome.
• Mandatory list of laboratory tests prior to surgery in traumatology.

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