Medial plica of the knee

What is medial parapatellar plica or medial plica of the knee?

The medial parapatellar plica, or medial plica of the knee, is a fibrous thickening on the inner side of the knee’s joint capsule. The plica connects the patella to the medial side of the joint capsule and represents a remnant of the embryonic blood vessel of the knee. While everyone has a medial plica, the anatomical size and clinical significance can vary significantly. Symptoms of the medial plica most commonly occur in adolescents. In symptomatic cases, the medial parapatellar plica is pronounced, with a taut edge rubbing against the femur during knee flexion, causing pain on the inner side of the knee.

How to diagnose the medial parapatellar plica or medial plica of the knee?

When coming to the pediatric orthopedic clinic, children or adolescents complain of pain on the inner side of the knee around the patella associated with activities. There are no clear memories of a serious injury or significant swelling in the knee, although many are involved in sports activities where they may fall on their knees or receive minor impacts on their legs. Some adolescents describe a “catching” sensation in the knee. On clinical examination, the knees appear normal (no swelling, redness, limited mobility, or signs of instability). However, there is tenderness upon palpation of the knee on the inner side of the patella. Occasionally, a painful thickening can be palpated. Adolescents with a symptomatic medial plica usually have shorter quadriceps muscles. If tenderness occurs with increased pressure on the femur near the patella and there is a recurring catching sensation with every knee movement, knee X-rays should be performed because similar symptoms are caused by osteochondritis dissecans (OCD) of the knee. However, the medial parapatellar plica is a soft tissue structure and cannot be seen on X-rays, so the child should be referred for knee magnetic resonance imaging (MRI).

How to treat the medial parapatellar plica or medial plica of the knee?

Painful medial parapatellar plica or medial plica of the knee is best treated conservatively with physical therapy. It is essential to limit activities that cause pain, and for active athletes, activities should be modified to avoid missing training processes. Physical therapy includes stretching exercises for quadriceps and hamstring muscles. Sometimes, the use of orthopedic insoles is advised to provide relief to the muscles of the lower leg, which can alleviate knee pain. If there is no improvement after three to four months of conservative treatment, and MRI clearly shows the medial parapatellar plica, surgical treatment is necessary. Arthroscopy of the knee is performed, where the medial parapatellar plica is cut and cleaned through two small incisions near the patella. After surgery, children immediately load the knee and quickly return to sports activities.

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