Osgood Schlatter Syndrome (OSS)

Introduction

This condition was first described separately in 1903 by two different physicians namely Osgood and Schlatter. It usually presents in growing children and teenagers with a gradual onset of pain, swelling and tenderness at the front of the knee. It occurs more commonly in boys than girls and it involves both knees in 20-30% if patients. In boys, the peak age of occurrence is between 12 and 15 while in girls it is between 8 and 12.

Pathology

OSS is considered a ‘traction apophysitis’, which means that a patch of bone just below the knee is repetitively strained by the strong pull of the quadriceps muscles during sporting activities. This patch of bone, as it is pulled away, continues to grow and enlarge. These two mechanisms are the cause of the patient’s pain and swelling.

Clinical features

Symptoms are often worse with sporting activities that involve jumping such as basketball, volleyball or when there is direct contact e.g. kneeling. Complaints may vary but usually patients present with a vague history of pain and swelling at the front of the knee. Initially symptoms are mild and intermittent however in an acute situation, the pain can sometimes be severe. Physical examination reveals tenderness and swelling at the tibial tuberosity, which is a bony bump located just below the knee. Pain may also be reproduced with resisted knee extensions.

Natural History

Once the acute phase of OSS passes and the pain and tenderness subsides, patients will often be left with a lump at the front of their knee. OSS is generally regarded as a self-limiting condition with 90% of patients’ symptoms resolving by themselves. It is important however to note that symptoms may come and go for as long as 12-24 months before it fully resolves. In 10% of patients, symptoms continue into adulthood despite all treatment measures.

Investigations

Although OSS is a clinical diagnosis, physicians often order X-Rays of the knee to exclude other more serious conditions. A lateral X-Ray of OSS will show bony separation of the tibial tuberosity in its early stages to separation in later stages.

Treatment

Initial treatment of OSS is conservative and non-operative. This includes ice, oral anti-inflammatory medications and protective knee padding if it improves symptoms.

In those with severe symptoms, activity modification may be prescribed to remove the patient from sport or exercise that aggravates their symptoms and redirected to another low-impact activity that maintains fitness e.g. swimming.

An exercise program may be included as part of treatment to improve flexibility. This should include a gradual introduction of hamstring and calf stretches to unload the front of the knee. High intensity quadriceps strengthening exercises can initially aggravate OSS and should be avoided until symptoms settle.