Kager’s fat pad, also known as the pre-Achilles fat pad, is an important structure at the back of the ankle. Sometimes it’s a direct source of pain, particularly in athletes and active people. More often, oedema within the fat pad is a sign of another problem, such as Achilles tendonitis. This article looks at the role of Kager’s fat pad, the causes and assessment of oedema, and how Kager’s fat pad oedema is managed.
What is Kager’s fat pad?
Kager’s fat pad is a triangular structure of fatty tissue at the back of the ankle, sitting between the Achilles tendon and the calcaneus (heel bone). It has several essential functions:
- Cushioning, to reduce friction between the Achilles tendon and the surrounding structures during movement
- Helping the Achilles tendon glide smoothly
- Shock absorption during activities such as running and jumping
Oedema or inflammation of Kager’s fat pad can result from overuse, trauma, or an underlying condition such as tendonitis, os trigonum syndrome, or inflammatory arthritis — leading to significant discomfort.
Assessing oedema in Kager’s fat pad
Symptoms of oedema in the fat pad include pain at the back of the ankle, swelling or tenderness over Kager’s fat pad, and discomfort when pointing the toe upwards. In many cases, the oedema is associated with another condition — such as Achilles tendonitis, os trigonum syndrome, or ankle joint arthritis — so these structures can be the true source of the pain.
On examination, your doctor finds swelling and tenderness of the fat pad, along with any of the other problems above.
Imaging usually detects the inflammation or oedema. Ultrasound shows the oedema, increased blood flow in the fat pad, and any tendonitis. MRI gives detailed images that confirm fat pad inflammation and rule out other conditions such as Achilles tendonitis, retrocalcaneal bursitis, or os trigonum syndrome. Sometimes blood tests are needed to rule out an underlying autoimmune or inflammatory arthritis.
Management of fat pad inflammation
Treatment aims to reduce the fat pad inflammation, usually by treating the underlying condition.
Activity modification is key. We avoid running and jumping, while cross-training activities such as cycling and swimming can continue. Heel raises and orthotics relieve pressure on the fat pad, and medication such as oral ibuprofen helps reduce pain and inflammation.
Specific treatments are used where there’s an underlying pathology. In Achilles tendinopathy, for example, a progressive calf-strengthening programme reduces Achilles swelling, which in turn reduces fat pad oedema. Heel raises and ankle-joint mobilisation help with os trigonum syndrome.
Injections
Occasionally, with severe Kager’s fat pad oedema, we use an injection to reduce inflammation. A cortisone injection into Kager’s fat pad reduces the oedema — but it must be used cautiously, given the risk of fat atrophy and Achilles tendon damage. Platelet-rich plasma (PRP) may promote healing and reduce chronic inflammation. We perform these injections under ultrasound guidance to improve effectiveness and reduce the risk of harm to surrounding structures.
Surgery is rarely needed, but where conservative measures fail, it may involve debridement or removal of inflamed tissue. Because Kager’s fat pad is an important protective structure, we avoid removing it unless all other measures have failed.
Frequently asked questions about Kager’s fat pad oedema
Is it common for fat pad oedema to occur without other ankle problems?
No. Fat pad inflammation usually occurs because of another problem around the fat pad — such as Achilles tendonitis, os trigonum syndrome, FHL tendonitis, ankle or subtalar joint arthritis, or a metabolic or autoimmune condition. So your doctor should look for and exclude these other causes.
What causes Kager’s fat pad oedema?
Most often,n it’s secondary to a nearby condition — Achilles tendonitis is the commonest — along with os trigonum syndrome, FHL tendonitis, ankle or subtalar arthritis, and inflammatory arthritis. It can also follow overuse or direct trauma to the back of the heel.
Is Kager’s fat pad oedema serious?
In itself, usually not — it’s more a marker that something else is going on at the back of the ankle. The important step is finding and treating the underlying cause, which is what settles the oedema and the pain.
How long does Kager’s fat pad oedema take to settle?
It depends on the underlying cause; for example, with calf strengthening for Achilles tendinopathy, the fat pad oedema typically improves over weeks to a few months.
Can I run with Kager’s fat pad oedema?
Usually not while it’s painful — we reduce running and jumping and switch to non-impact cross-training such as cycling and swimming until it settles. A graded return follows once the underlying cause is under control.
How is Kager’s fat pad oedema treated?
By treating the cause, alongside activity modification, heel raises or orthotics, and anti-inflammatories. A cautious ultrasound-guided injection is reserved for severe cases, and surgery is rarely needed.
Final word from Sport Doctor London about Kager’s fat pad oedema
Kager’s fat pad oedema can cause real discomfort and affect performance, but it’s usually a sign of another problem at the back of the ankle rather than a condition in its own right. Early diagnosis — through clinical assessment and imaging — and a plan aimed at the underlying cause lead to effective relief and a return to activity.
If you have pain at the back of the ankle, Dr Masci can assess you in London, including an in-clinic ultrasound. Contact the team here or call +44 (0) 203 488 0350.
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