Sinding-Larsen-Johansson syndrome is characterized by inflammation of the kneecap (patella) at its lowest point in the area of the growth center. This is the site of origin of the patellar tendon. There is traction on the kneecap at this point due to the action of the large, powerful thigh muscle (quadriceps), as well as with deep bending of the knee. The injury is usually due to repeated stress or vigorous exercise.
Sinding-Larsen-Johansson syndrome results from stress (a single sudden incident or repeated) or injury of
the lower patella that interferes with development, causing inflammation. This may be inflammation of the
cartilage of the growing patella, death of tendon cells from repeated stress, or pulling off of the lining of the
patellar bone.
Mild cases can be resolved with a slight reduction in activity level, whereas moderate to severe cases may require significantly reduced activity (12-16 weeks) and even immobilization (cast/brace) at times. Initial treatment consists of medications and ice to relieve pain, stretching and strengthening exercises, and modification of activities. Specifically, kneeling, jumping, squatting, stair climbing, and running on the affected knee should be avoided. The exercises can all be carried out at home for acute cases. Chronic cases often require a referral to a physical therapist or athletic trainer for further evaluation or treatment.
Uncommonly, the affected leg may be immobilized for 6 to 8 weeks (in a cast, splint, or reinforced elastic knee support). A patellar band (brace between the kneecap and tibial tubercle on top of the patellar tendon) may help relieve symptoms. Rarely, surgery is needed (if conservative treatment fails) in the growing patient. In addition, surgery may be necessary after skeletal maturity if the ossicle becomes painful.
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