bubble_chart Overview

Direct trauma to the knee can cause patellar cartilage or osteochondral fractures, or repeated injuries, such as sports injuries, leading to degenerative changes in the cartilage, making the cartilage surface rough and losing its luster. In severe cases, the cartilage may detach, exposing the bone, and the opposing femoral joint surface may also be injured. The injury site is often located in the center of the patella. This condition mostly occurs in young adults and is often associated with a clear history of trauma or chronic cumulative minor injuries. The main symptom is pain behind the patella in the knee joint, varying in severity. Generally, walking on flat ground does not show obvious symptoms, but pain worsens when squatting, standing up, climbing stairs, walking on slopes, or after long-distance walking.

bubble_chart Clinical Manifestations

1. Patellar Grinding Test During the examination, the patella and its corresponding femoral condylar articular surface are compressed and ground against each other or slid up, down, left, and right. A rough grinding sensation, friction sound, and pain or discomfort may be felt. Alternatively, the examiner may forcefully push the patella to one side with one hand while pressing the posterior edge of the patella with the thumb of the other hand, which can also induce pain.

2. Single-Leg Squat Test The patient bears weight on one leg and gradually squats to 90°–135°. Pain and weakness may occur, and the patient may be unable to stand up from the squatting position using only the affected leg.

X-ray Examination: Anteroposterior, lateral, and tangential patellar views of the knee joint are taken. No abnormalities are seen in the early stages. In the advanced stage, due to extensive cartilage wear, the space between the patella and femoral condyle narrows, and osteophytes may form at the edges of the patella and femoral condyle.

The main diagnostic criteria for chondromalacia patellae are posterior patellar pain, pain induced by the patellar grinding test, and pain during the single-leg squat test. It is important to check for concurrent conditions such as meniscus injury and traumatic arthritis.

bubble_chart Diagnosis

There is a clear history of trauma or chronic cumulative minor injuries, with the main symptom being pain behind the patella of the knee joint.

bubble_chart Treatment Measures

Non-surgical therapy: For those with mild symptoms, it is important to avoid direct impact on the patella and reduce activities that cause patellar friction, such as hiking, climbing stairs, or cycling. These measures can help alleviate symptoms.

Surgical therapy: For those with severe symptoms, timely surgery is recommended. The appropriate procedure should be chosen based on the condition of the patella.

1. Patellar cartilage shaving: This includes superficial cartilage shaving, shaving down to the subchondral bone, and bone drilling.

(1) Superficial cartilage shaving: A sharp blade is used to shave away degenerated cartilage until healthy cartilage is reached. Although the regenerative capacity of cartilage is limited, after several months of remodeling, the surface becomes smooth and covered with layers of flattened cells, leading to satisfactory surgical outcomes.

(2) Shaving down to the subchondral bone: If cartilage damage extends to the bone, the full thickness of the cartilage can be shaved, and the edges of the wound can be beveled. The exposed bone is left untreated. Full-thickness cartilage defects that do not reach the medullary cavity may undergo slow endogenous regeneration, producing hyaline cartilage.

(3) Shaving down to the subchondral bone and drilling: After removing the diseased full-thickness cartilage, several holes are drilled into the exposed bone using Kirschner wires to induce bleeding from the bone bed. Full-thickness articular cartilage defects extending to the medullary cavity can achieve exogenous repair from mesenchymal tissue in the medullary cavity.

These procedures can be performed arthroscopically using a shaver or via open arthrotomy under direct visualization.

2. Patelloplasty: After shaving away the diseased cartilage, if the exposed bone area is large (2–3 cm), adjacent synovium or a layer of fat pad can be harvested and sutured over the exposed bone surface.

3. Patellectomy: For older patients with severe symptoms, large areas of exposed bone (exceeding 3 cm), and significant wear of the opposing femoral condyle cartilage, patellectomy may be considered if patelloplasty is not feasible. {|108|}