Bipartitie Patella - Congenital Split in The Kneecap

kneecap
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A bipartite patella occurs when the patella, or kneecap, occurs as two separate bones. Instead of fusing together in early childhood, the patella remains separated. A bipartite patella is usually not a problem; it occurs in about 2-3% percent of the population.

The Kneecap

The kneecap--or properly named, the patella--is a type of bone called a sesamoid bone.  Sesamoid bones are enveloped within a tendon.

  The patella is within the quadriceps tendon and it has three important functions:

  1. It is a fulcrum to increase power of the knee joint
  2. It protects the knee from trauma
  3. It's cartilage surface lubricates and provides nutrition for the knee joint

Normally, the patella is formed from one ossification center, a place that forms bone in fetal development and early childhood.  In some, a secondary ossification center forms, and this may not fuse with the primary ossification center.  In these people, the patella forms as two separate bones.

Signs of Bipartite Patella

Most people with this condition never have any symptoms.  However, in some people who have a bipartite patella, the fibrous tissue that connects the pieces of bone can become inflamed and irritated. The tissue that connects the two parts of bone is called a synchondrosis.  The symptoms of knee pain that can develop are usually the result of a direct injury to the kneecap, or repetitive strain on the synchondrosis.

  Common symptoms of an inflamed bipartite patella include:

  • Pain directly on the kneecap
  • Swelling at the synchondrosis
  • Painful range of motion of the knee

A bipartite patella is most commonly diagnosed as an incidental finding, meaning it is noticed on an x-ray or MRI that was performed for diagnosis of symptoms unrelated to the kneecap.

In people with no symptoms related to the bipartite patella, nothing further needs to be done.

If people do have symptoms related to their bipartite patella, they will often have x-rays to identify the abnormal kneecap.  An MRI can be helpful to determine the amount of inflammation surrounding the bipartite patella.  A bone scan is another test that can be used to detect the degree of inflammation around the abnormal patella, although most physicians are currently using MRI rather than bone scans.

Treatment Options

In most cases, no treatment is needed for patients diagnosed with a bipartite patella. If there are symptoms related to inflammation of the synchondrosis of the bipartite patella, treatment may be pursued to try to calm the inflammation of the kneecap.  These treatments are likely to include:

  • Rest: Allowing the kneecap to rest is the first step in treatment, and often the only step necessary to resolve the symptoms of this condition.  Rest may include immobilization of the knee in a slightly bent position to take pressure off the kneecap.
  • Ice Application: Decreasing inflammation and relieving pain are often accomplished with the application of cold packs directly to the front of the kneecap.
  • Anti-Inflammatory Medications:  Oral medications can be used to help relieve pain and reduce inflammations.  Typically nonsteroidal anti-inflammatory medications (also called NSAIDs) are used to help calm the irritated kneecap.  In more severe cases, a cortisone injection, also a powerful anti-inflammatory medication, can be administered to help address the problem.
  • Compression Knee Braces:  Knee braces can help to limit mobility and support the kneecap.  A simple patellar compression knee brace is often the most helpful type of brace for this condition.

In the few patients who develop persistent symptoms as a result of their bipartite patella, there are surgical treatment options. Most surgeons recommend trying nonsurgical treatment options for a minimum of 6 months prior to considering any surgical solution.  The surgery usually consists of removing the smaller fragment of bone or detaching the muscle that inserts on the smaller piece of bone.

Sources:

Gaheer RS, et al. "Contemporary Management of Symptomatic Bipartite Patella" Orthopedics; Vol. 32, No. 11; November 2009. Pages 843-9.

Atesok K, Doral MN, Lowe J, Finsterbush A. "Symptomatic bipartite patella: treatment alternatives" J Am Acad Orthop Surg. 2008 Aug;16(8):455-61.

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