A bipartite patella happens when our kneecap is made up of two separate bones, instead of the usual and normal one piece. What causes this is that the patella failed to fuse together during childhood.
It is a fairly rare condition, affecting only 1-2% of the
Fortunately, in most cases, a bipartite patella does not cause any knee problems and may in fact, go completely unnoticed...it's usually and often only discovered when an x-ray is done for an unrelated knee problem or like a regular check up.
That being said, in some instances it can cause knee pain at the front of the knee, especially when squatting down, and can limit knee movements and function.
In this article, we will look at
The patella, or kneecap, is a triangular shaped bone.
When we're born, there is essentially no bone in the kneecap – it is made up entirely and 100% of
cartilage and blood vessels only. As we grow over time and over early childhood years, our kneecap cartilage gradually expands.
Around age 4 years old, our knee cartilage will start to ossify, forming small
portions of bone. These bone segments will slowly and gradually fuse together and by the
age of 12 we will have a single kneecap (that is single one piece) formed.
Sometimes, like in the case of bipartite patella, what happens is that the bones fail to fuse completely leaving two distinct pieces of bone. Typically there tends to be one large piece of bone and one smaller fragment.
Unfortunately no one knows why it happens, just that we know how it happens, and that the two portions of bone remain unfused, connected by fibrocartilaginous tissue known as synchondrosis.
Bipartite patella is more common in males with a male:female ratio of 9:1 (that is it happens in males 9x more than females).
The first classification system for bipartite patella was introduced
in 1921 by Saupe. What he did was that he used the location of the fragment to classify the
condition into three types:
Type 1: where fragment is at the inferior (bottom) portion of the patella. Incidence approximately 5% of the time
Type 2: where fragment is found on the lateral margin (outer side) of the patella. Incidence approximately 20% of the time
Type 3: The bone fragment is at the superolateral (upper, outer) portion of the patella. Incidence approximately 75%
as you can see, by far the most common place to have the synchondrosis
is at the top of the kneecap, on the outer side, type 3.
In approximately 98% of cases of bipartite patella, people are completely asymptomatic - this means that there are typically NO symptoms of knee issues or pain.
And in most cases, patients are not even aware they have such a condition, and they just found it about this condition when they got their knees x-rayed or scanned for
But...in 2% of bipartite patella cases, patients do develop knee symptoms and problems.
This usually happens when the cartilage tissue between the bones, the synchondrosis, is damaged, leading to knee
This is typically results from
Activities that typically cause problems are those where there is repetitive knee bending, jumping or squatting such as with
The most common symptoms that people do experience with symptomatic bipartite patella are:
1) Knee Pain:
usually at the top of the patella on the outer side of the knee. It
tends to gets worse with squatting activities as more force goes through
the kneecap with squatting and lunges
2) Tenderness: when first and direct pressure is placed over the bony fragment
3) Knee Swelling: this tends to be fairly localized to where the patella is
4) Instability: the knee may feel unstable, like it is going (or seems to be easily) to give way
5) Bony Ridge: you may be able to feel a slight ridge on the patella
6) Large Patella: The kneecap may well be larger than usual
The unfused area of the kneecap will shows up clearly on an x-ray or MRI scan of the knee. The triangular bone will have a gap in it where the fibrocartilaginous tissue has failed to ossify.
It may initially be mistaken for a patella fracture but the tell-tale signs of bipartite patella are:
Most symptomatic cases can be treated conservatively i.e. non-operatively. Treatment for bipartite patella usually consists of:
It is important to rest from all aggravating activities. If an
activity causes or aggravates knee pain, it is best practice to not continue that specific task or activity. The painful knee joint needs time to settle down
so it can heal.
2) Ice / Cold Therapy
Regularly applying ice to the knee can help to reduce inflammation in the synchondrosis.
It is really important to strengthen and stretch the knee muscles to
allow the kneecap to move properly without the synchondrosis getting
irritated and inflamed.
4) Knee Brace
Another thing that can help is to wear a knee brace to unload the kneecap and reduce the force that goes through the knee synchondrosis. In some cases the knee may be immobilised in a brace that holds the knee in 30 degrees of flexion.
5) Steroid Injections
In some cases your orthopedic doctor may give you an injection of corticosteroid mixed with local anaesthetic to reduce pain and inflammation. The knee usually feels instantly better but the effects can be short-lived.
Your doctor may prescribe painkillers and anti-inflammatory medication can help to reduce any knee pain and inflammation.
Regular session of knee physical therapy with our senior physiotherapists can also be helpful to reduce pain and inflammation and to address any areas of muscle weakness around the knee.
What they will do is to work on a knee rehab programme with you and may also use ultrasound therapy to help reduce inflammation and improve healing.
usually settle after two or three months with these treatment methods.
However if they persist for more than six months then your doctor may
advise you to consider corrective knee surgery.
Patients may also receive the following physiotherapy treatment modalities: