What is the medial plica?
The medial parapatellar plica (medial plica) is a fibrous thickening of the inner part of the knee joint capsule on its medial side. It connects the patella to the medial capsular wall and represents a remnant of the embryonic blood vessel of the knee. Although everyone has a medial plica, its anatomical size and thus clinical significance vary considerably.
Symptoms most commonly occur in adolescents. In symptomatic cases the plica is prominent with a taut edge and rubs against the femoral condyle during knee flexion, causing medial knee pain.
Diagnosis
Children or adolescents present with medial knee pain near the patella related to activity, with no clear recollection of significant injury or swelling, although many participate in sports involving falls or minor impact. Some describe a snapping sensation during knee movement.
On examination the knee appears normal externally – no swelling, redness, restricted motion or instability. However, tenderness is found on palpation of the medial patellar border. A painful thickening may sometimes be palpated directly.
Adolescents with symptomatic medial plica often have tight quadriceps muscles. If pain occurs on firm pressure near the patella with a repeated snap on each knee movement, X-ray should be performed because similar symptoms can be caused by osteochondritis dissecans (OCD) of the knee.
The medial plica is a soft-tissue structure not visible on X-ray. MRI is required for confirmation of the diagnosis and to rule out other causes of medial knee pain.
Treatment
Treatment is best started conservatively with physiotherapy. Activities causing pain should be restricted; in active athletes, training should be modified rather than stopped entirely.
Physiotherapy includes stretching exercises for the quadriceps and calf muscles. Orthotic insoles sometimes provide relief and pain resolves completely.
If there is no improvement after 3–4 months of conservative treatment and MRI clearly shows the medial plica, surgery is indicated.
Surgical treatment
Surgery consists of arthroscopic resection of the plica through two small portals next to the patella. The procedure is minimally invasive and effective – the thickened plica is removed entirely, eliminating the source of friction and pain.
After surgery children immediately bear weight on the leg to the limit of pain and return to sport quickly, typically within a few weeks.