Three Causes to Consider with Chronic Knee Pain in Young Athletes

Pain in the front of the knee is a very common and often frustrating occurrence in children who participate in running, jumping/leaping and turning activities. When sensible treatment strategies such as rehabilitation exercises, ice, activity modification, and time just don't seem to be creating pain, consider the following three causes of chronic anterior knee pain.

1) Osteochondral Lesions

Articular cartilage is thin tissue that covers the ends of the thigh bone (femur), shin bone (tibia) and backside of the kneecap (patella). An osteochondral lesion is damage to that creates crescent-shaped fragments (look like "shark-bites") of bone and cartilage that is most extreme cases may separate from the bone of origin and float within the knee joint. Symptoms may mimic more common anterior knee pain, though locking, catching, and local swelling are more suggestive of osteochondral damage. 

Osteochondral lesions can be initially identified on plain x-rays, which must include the tunnel view which best visualizes the lower thigh bone.  Have seen cases where not obtaining the tunnel leads to missed opportunities to identify injury, such at the osteochondral lesion identified on the inside of the femur seen on the x-ray image above.  Magnetic Resonance Imaging (MRI) is often used to better characterize size and nature of lesions.

Management of osteochondral lesions depends on several factors:

• Age of the patient: children with open growth plates tend to have better chance of non-surgical repair
• Size of the lesion
• Present of separation of fragment from bone of origin
• Location: fragments on the inside of the femur tend to have the best outcomes, while fragments on the outside of the femur tend to have less optimistic outcomes and those on the back of the patella tend to have the most difficult outcomes.

2) Anterior Fat Pad Impingement

Image courtesy of http://www.physiotherapy.co.uk/blog/wp-content/uploads/2011/09/hoffas_impingement1.gif

Located below the patella and behind the patellar tendon between the femur and tibia (see yellow shaded region in adjacent picture), an enlarged or irritated anterior fat pad can become trapped and cause pain especially with bending of the knee.  More commonly seen in adolescents, this is often best identified by direct finger-tip pressure placed on either side of the patellar tendon with the knee bent to about 90 degrees.

While identification of fat pad impingement can be a challenge, treatment is also fraught with unique potential challenges. Direct injection of anesthetic and anti-inflammatory medication can help both with diagnosis and pain relief, but often the initially promising results wear off within a few months. Surgical excision of the fat pad is a reasonable next option, but regrowth of the fat pad commonly can occur.

3) Placing Too Much Focus on the Knee

When the knee hurts, seems logical to put direct emphasis on correcting problems at that joint. However, failing to evaluate and respond to mechanical issues above and below the knee can slow progress and prolong pain and frustration.

• Hip/Buttock: Inadequate strength of the buttock gluteal and hip external rotator muscles can lead to abnormal positions of the knee and place undue forces particularly on the patella. Proper attention to the hip and buttock is essential for long-term resolution of anterior knee pain.
• Great Toe: Amazing to realize how much dysfunction can occur with limited motion of the metatarsophalangeal joint of the big toe. Restricted movement can also place unnecessary forces on the patella.

This article is not designed to provide any diagnosis or treatment recommendations. Seek qualified pediatric sports medicine speciality evaluation to help young athletes properly identify factors causing chronic anterior knee pain and provide potential solutions.