A bipartite patella means that the patella (knee cap) is two separate bones instead of being the usual one piece; because it failed to fuse together properly during childhood.

That’s why this is a pretty rare condition, which affects only 1-2% of the general population.

The good news is that most of the time, a bipartite patella doesn’t cause much knee problems. In fact, most of the time, patients dont even realize simply because there’s no symptoms (it’s discovered typically during routine checkups or unrelated knee problems.)

That being said, sometimes it can cause knee pain where the knee cap is (front of the knee), usually when one squats. It can also decrease knee movements too.

What causes bipartite patella?

Upon birth, there is no bone is in the knee cap.

Over time and early childhood years, our knee cap cartilage grows and expands. It’s this knee cartilage that will start to ossify (become bony), forming small portions of the bone.

These bony segments will gradually fuse together by the time we’re 12 years old where it’d end of in a single kneecap.

Sometimes, such like in bipartite patella, these bony segments do not fuse completely, leading to two distinct pieces of patella bones in one knee (most of the time it’s a larger and a smaller bone piece).

Unfortunately no one knows for sure why exactly it happens, just that two portions of bone remain unfused and connected by fibrocartilaginous tissue known as synchondrosis.

Bipartite patella happens in males 9x more than females.

Types of bipartite patella

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%

The most common place to have the synchondrosis is at the top of the kneecap, on the outer side, type 3. In about 50% of the patients, both knees are affected with the same type or classifications of bipartite patella.

Bipartite patella symptoms

Majority of patients with bipartite patella have no symptoms…and we’re talking about 98%, leaving only a very small minority of patients who do get knee pains because of this condition. This usually happens when the cartilage tissue between the bones, the synchondrosis, is damaged, leading to knee irritations and inflammation.

Most of the time, there’s a reason, be it

• a direct blow to the front of the knee
• a fall or
• repetitive overloading at the knee.

Activities that typically cause problems are those where there is repetitive knee bending, jumping or squatting such as with skiing, cycling, hill walking or baseketballs with lots of jumping and landing.

The most common symptoms that people do experience with symptomatic bipartite patella are:

1. Knee pain located 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 with direct pressure is placed over the bony fragment
3. Knee swelling this tends to be fairly localized to where the patella is
4. Knee 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. Enlarged Patella The kneecap may well be larger than usual on the affected knee

Diagnosing Bipartite Patella

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.

Sometimes it be may be mistaken for a patella fracture but the tell-tale signs of bipartite patella are:

• Rounded Edges: as compared to the characteristic jagged edges seen in patella fractures
• Location: A gap on the superolateral aspect of the kneecap is characteristic of bipartite patella rather than a fracture
• Bilateral: If both knees show similar findings on x-ray it is most likely bipartite patella rather than a fracture (not common to have TWO patella fractures at the same time)

Treatment options for bipartite patellar knees

Most symptomatic cases can be treated without surgery with

1. Rest – It is important to rest from all aggravating activities. If an activity causes or aggravates knee pain, dont continue that specific task or activity (at least in the beginning, for now). We need to allow 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 and will bring down knee pain levels.
3. Knee Brace – a knee brace can help decrease load and stress on 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.
4. 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.
5. Medication – Your doctor may prescribe painkillers and anti-inflammatory medication can help to reduce any knee pain and inflammation. It’s not recommended for long term, but short term it can help a lot with physical therapy and exercise.
6. Knee Pain Physical Therapy – 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.

Symptoms usually settle after two or three months with these treatment methods. However if the knee pain from your bipartite patella lingers more than 6 months (180 days) then you may have to consider corrective knee surgery.

Patients may also receive the following physiotherapy treatment modalities:

• cold therapy
• moist heat paraffin wax therapy
• radio-frequency
• joint mobilization
• stretching exercises
• strengthening exercises
• scar management
• hands on manipulation and mobilization (manual therapy)
• soft tissue management
• heat therapy and heat treatment and heat pack to relief tight muscles and joints
• ultrasound therapy to accelerate soft tissue healing
• exercise therapy
• acupuncture and/or dry needling
• deep tissue release
• and more

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