Chondromalacia Patellae

What It Is, Causes, Signs and Symptoms, and More

Author: Emily Miao, MD, PharmD

Editor: Alyssa Haag, MD

Editor: Józia McGowan, DO

Editor: Kelsey LaFayette, DNP, ARNP, FNP-C

Illustrator: Jannat Day

Modified: Jan 06, 2025

What is chondromalacia patellae?

Chondromalacia patellae is a radiologic diagnosis characterized by pathologic wear and tear of smooth cartilage underneath the patella or kneecap. The term is commonly used interchangeably with patellofemoral pain syndrome, a musculoskeletal condition that affects the knee joint and is often associated with overuse injury in young, athletic individuals. Knee pain in individuals with chondromalacia patellae is aggravated by high-impact, weight-bearing activities that involve an increased load on the patellofemoral joint while the knee is flexed (e.g., running, squatting, prolonged sitting).

An infographic detailing the background, causes, risk factors, signs and symptoms, diagnosis, and treatment of chondromalacia patellae.

What causes chondromalacia patellae?

Chondromalacia patellae may be caused by several etiologies including weakness of the core and thigh muscles; recurrent joint injuries or trauma, such as repetitive bending or twisting of the knee joint during sports; or iatrogenic injection of medications (e.g., steroids) into the knee joint. Weakness or imbalance of any of the major thigh muscles (e.g., pectineus, sartorius, or quadriceps femoris) can lead to improper weight distribution or loading on the knee joint, leading to inflammation and cartilage damage. Cartilage serves as a protective cushion for the bones in the knee and when substantial erosion occurs, the kneecap’s bony surface can grind painfully against other bones.

Chondromalacia patellae is more prevalent in young adults compared to any other age group. It is also common in runners, athletes who bear weight while the knee is flexed, and individuals who spend the majority of their time kneeling (e.g., gardeners).

What are the signs and symptoms of chondromalacia patellae?

The most common symptoms of chondromalacia patellae are poorly localized, aching pain in the anterior portion of the knee that is exacerbated by flexing the knee (e.g., when going up and down a flight of stairs). The knee may be stiff and/or painful after prolonged sitting. If the articular damage is severe, crepitus (i.e., popping or clicking sound produced by bones rubbing against one another) or a knee effusion (i.e., buildup of fluid) may be present.

How is chondromalacia patellae diagnosed?

Diagnosis of chondromalacia patellae begins with a thorough history of present illness, review of symptoms, and a medical history that elicits a prior history of knee infection, injury, or surgery. A musculoskeletal physical exam is performed to assess for the presence of swelling, deformity, tenderness, and/or fluid surrounding the knee joints. The patellar grind test, which detects the presence of patellofemoral joint disorder, may be positive (i.e., Clarke’s sign) if the individual is unable to contract the quadriceps with downward pressure on the kneecap. Knee X-rays may be helpful to exclude a fracture, while computed tomography (CT) or magnetic resonance imaging (MRI) of the knees are used to confirm radiologic features (i.e., focal areas of edema; loss of cartilage tissue, represented by hyperintense signals; cartilage surface irregularity and fragmentation; and exposure of subchondral bone) of chondromalacia patellae. CT or MRI can also be used to exclude differential diagnoses that can present with overlapping features (e.g., meniscus tear). In cases where there is suspicion of a joint infection or effusion, an arthroscopy which is both diagnostic and therapeutic, may be performed, where a tube-like instrument with a camera is inserted into the knee through a small opening to visualize gross pathology, debride the joint, and remove the fluid.

How is chondromalacia patellae treated?

Treatment and prevention of chondromalacia patellae consists of a combination of lifestyle modifications and pharmacologic options. Lifestyle modifications include stretching prior to athletic activities, wearing cushioned knee pads while kneeling, and avoiding excessive high-impact exercises. Pharmacologic options such as non-steroidal anti-inflammatory medications (e.g., ibuprofen, aspirin) and pain relievers (e.g., acetaminophen) can help with reducing pain. A referral to a physical therapy specialist can also help individuals develop a safe exercise program aimed at strengthening abdominal, thigh, and leg muscles. If conservative measures fail, then a surgical procedure such as joint arthroscopy may be required to remove the damaged cartilage. For severe, refractory symptoms, patellar realignment surgery (i.e., a procedure that restores the biomechanical force axis of the patellofemoral joint) and patellectomy (i.e., surgical removal of the patella) may be offered.

What are the most important facts to know about chondromalacia patellae?

Chondromalacia patellae is a radiologic diagnosis characterized by pathologic wear and tear of smooth cartilage underneath the patella and the term is used interchangeably with patellofemoral pain syndrome. Chondromalacia patellae can be caused by weakness of the core and thigh muscles; recurrent joint injuries or trauma such as repetitive bending or twisting of the knee joint during sports; or injection of medications into the knee joint. Signs and symptoms include dull, aching pain in the anterior portion of the knee which worsens with knee flexion. Diagnosis is confirmed when radiologic findings are seen on a CT or MRI scan. Treatment includes a combination of lifestyle modifications, short-term non-steroid anti-inflammatory medications, and physical therapy. In refractory cases, surgery may be warranted to remove the damaged cartilage.

References

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