Knee Pain: Fat Pad Irritation or Hoffa’s Syndrome

 

Fat pad irritation (Hoffa’s syndrome) is a condition that falls under the broad umbrella of knee dysfunction leading to anterior knee pain.

It is a potential source of pain referral to the anteromedial knee .

Because of the proximity of the fat pad to other structures such as the patella tendon, it can sometimes be misdiagnosed as patella tendinopathy.

There are however signs and symptoms that are unique to an individual with fat pad irritation, allowing for the diagnosis of this condition. It is a fairly simple condition to treat, once accurately diagnosed, as long as the causative factors are recognized and managed.

Physiotherapy treatment includes local cryotherapy, taping, local muscle flexibility and strengthening exercises, and correcting lower limb biomechanics to reduce symptoms.

Mechanism Of Injury

The richly innervated fat pad located just below the kneecap can become irritated due to direct trauma to the anterior aspect of the knee or can occur overtime. 

Excessive knee hyperextension can predispose the knee to infrapatellar fat pad (Hoffa’s fat pad) impingement. One contributing factor is anterior pelvic tilt, which is commonly observed in individuals who frequently wear high heels. This posture shifts the body’s alignment forward and often pushes the knee into a recurvatum (hyperextended) position during standing.

At the same time, this biomechanical position can lead to shortening of the quadriceps muscle group, particularly the rectus femoris. A tight quadriceps can pull the patella superiorly, which may tilt the inferior pole of the patella posteriorly toward the fat pad. If the patellar tendon is already taut, such as in individuals with pre-existing patellar tendinopathy, the posterior pressure on the fat pad can increase further. Because of this, fat pad irritation may sometimes coexist with or be mistaken for patellar tendinopathy.

Signs And Symptoms

Patients can present with an acute or chronic complaint of sharp pain in the infrapatella region.

A patient will often complain of pain with walking, prolonged standing, wearing high heel shoes, in fact, any activities that put their knee into full extension.

Clinical Signs Of A Fat Pad Impingement

Clinically, individuals with fat pad impingement may present with anterior knee pain just below the patella, tenderness on either side of the patellar tendon, mild swelling or fullness at the front of the knee, and discomfort when the knee moves into full extension or hyperextension. Some patients may also adopt a slightly flexed knee posture to avoid compressing the fat pad.

Conversely, patients will report significant relief if the inferior pole of the patella is tipped up and away from the fad pad, which is achieved by pushing the superior border of the patella posteriorly. This has a see-saw effect of subsequently lifting the inferior pole of the patella. This offloads the fat pad from direct pressure from the patella, relieving symptoms.

Biomechanical factors that are therefore important to assess include genu recurvatum (knee hyperextension), anterior pelvic tilt, and quadriceps tightness, as these can increase the likelihood of fat pad irritation.

Differential Diagnosis Of Fat Pad

Fat pad impingement can be mistaken as patella tendinopathy at first glance because of the location of the pain. The latter tends to produce localised pain on palpation of the tendon which can be easily palpated unlike the fat pad which is located deep to either side of the patella tendon.

Stressing the patella tendon with resistance to the quadriceps, e.g. doing a squat, reproduces pain to the tendon. Wearing a patella tendon band increases the pain to the fat pad but brings relief to patella tendinopathy.

Hoffa’s test is a useful diagnostic test to confirm the source of pain being likely from the Hoffa’s fat pad and not the patella tendon. If the pain increases with activation of quad muscles this may be more indicative of a patella tendon condition.

Management Of Inflammed Fat Pad

Swelling management

The initial treatment for an inflammed fat pad is to manage the swelling and inflammation. Ice can be applied to the infrapatella region for approximately 15-20 minutes for 2-3 times a day. This is to be done for about an hour apart, especially at the end of the day. Therapeutic ultrasound with iontophoresis using anti-inflammatory gel can also help to bring down the swelling. Once the swelling reduces, the condition is a lot easier to manage due to a reduction in pain.

Taping

A commonly used taping technique involves lifting up the inferior pole to offload the fat pad and prevent impingement.

As shown in the pictures above, the medial and lateral border of the patella is pulled diagonally upwards to sling the patella superiorly. The superior border will be taped across horizontally. This is to tilt the inferior pole away from the fat pad. This provides mechanical relief to the fat pad, giving it an environment to heal. Depending on the type of tape, this may restrict full knee extension hence should only be used in the early phases post injury. Depending on the situation, the physiotherapist may decide to use an elastic tape – like Kinesio tape – rather than rigid tape to offload the fat pad.

Taping techniques to prevent excessive hyperextension of the knee is also a useful option. This is especially so in the acute phase of the injury. This will help reduce individual symptoms, which allows for the other factors to be treated.

Stretching

Management of fat pad impingement also requires regime of quadriceps stretching and myofascial release, specifically the rectus femoris. This will help in offloading the inferior pole.

Strengthening

Progressive strengthening of the quadriceps especially at the end ranges of knee extension is important to reduce hyperextension in functional tasks and reduce posterior tilting of the inferior pole of the patella.

Biomechanics

Other than treating the localized inflammation and realigning the patella, the biomechanical factors also need addressing. Advice to avoid heels may be recommended. This is because the tiptoe position with in high heels encourages the knee to hyperextend, and the pelvis to go into anterior tilt.

Hodges et al found that pain in the fat pad changes motor control of the quadriceps muscle when ascending and descending stairs. Without proper control of the quadriceps, the chances of recurrence of fat pad impingement are high due to increased instability of the knee as a result. Hence, strength training for the quadriceps should include stability training to improve on the control and coordination of the quadriceps.

Experiencing knee pain? Click here to find out more about physiotherapy for knee pain relief and how Core Concepts can help.

 

References

Brukner P and Khan K (2004) Clinical Sports Medicine. 2nd ed Anterior Knee Pain. McGraw-Hill. Chap 24 Pg 480-481.

Hodges PW, Mellor R, Crossley K, Bennel K, Pain induced by injection of hypertonic saline into the infrapatellar fat pad and effect on coordination of the quadriceps muscles. Arthritis Care & Research 2009. Vol 6: Issue 1: 70–77