A 30-year-old woman who presents pain with hyperextension of the knee and by pressing on the lower pole of the patella.
Inflammatory changes in Hoffa fat located between the lateral femoral condyle and the patellar tendon (figures 1, 2 and 3). The patellar tendon shows discrete lateralization. High patella is also observed (Insall-Salvati Index 1.4;figure 4). The described findings are compatible with lateral femoral condyle-patellar tendon friction syndrome.
Frequently underdiagnosed, the patellofemoral friction syndrome, also called Hoffa's fat cushion compression syndrome, is mainly represented by 2 characteristic symptoms, which are mainly found in women (especially if they present obesity or rapid weight gain, as in pregnancy): patellofemoral pain and instability in the patellar region [1].
Edema of the superolateral Hoffa fat pad is associated with pathology of the patellofemoral region, such as malalignment and friction syndrome (object of this clinical case).
This pathology that must be diagnosed with MRI, since MRI is the imaging technique of choice for the diagnosis of this entity. Radiographs and CT are usually normal. [1, 2]
The upper patella, the increased distance TT-TG (distance between the anterior tuberosity of the tibia and the deepest part of the femoral trochlea), and a short distance between the lateral trochlear (external) facet and the patellar ligament, this is, the distance PL-T [1, 4].
The upper patella and the distances described are also independent predictors of the appearance of a hypertensive signal that translates oedema in the Hoffa fat region.
In addition, once the hyper signal in Hoffa's fat is detected, the lateral aspect of the patellar ligament should also be assessed in an active search for pathology indicative of focal tendinopathy [3]
The most typical image findings of this entity is a hyperintense focal area on STIR and T2-weighted sequences (representing the oedema on the inferolateral aspect of the femorotulin joint), in the region included in the most superolateral portion of the infrapatellar fat of Hoffa. It is not uncommon to find a lesion of a cystic nature located between the lateral retinaculum and the external femoral condyle, but this finding is not too frequent [1, 4].
Associated findings: high patella;lateral patellar subluxation. These superimposed findings can appear in >90% of patients.
The edema in the superolateral region of the fat of Hoffa is should make us suspect that there is a femorotullar misalignment, with the distances described above altered. In addition, when there is oedema, there is a tendency to present greater external deviation of the patella and the existence of a trochlear groove that is less deep than normal (to assess signs of trochlear dysplasia). The existence of less deep trochlear grooves or external subluxations will cause a greater friction (excessive if the syndrome appears) in the region of the external femoral condyle and the superolateral zone of the infrapatellar fat [4].
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Patellofemoral friction syndrome.
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The patient is a 30-year-old female who complains of pain upon knee hyperextension and when pressing on the inferior pole of the patella. MRI shows that in the patellofemoral articular surface at the lateral patella and corresponding area of the lateral femoral condyle, there is a prominent hyperintense signal in Hoffa’s fat pad (especially in its superolateral portion) on T2-weighted and STIR sequences, indicating edema or inflammatory changes. In addition, the patella is positioned higher (high patella), and there are signs of mild lateral patellar subluxation and possible shallow femoral trochlea.
No obvious bony destruction or large-area cartilage defects are noted, but the hyperintense region in the superolateral portion of the fat pad may be associated with patellofemoral malalignment.
Taking into consideration the patient’s age, clinical symptoms (pain with knee hyperextension and tenderness at the inferior pole of the patella), and imaging findings (significant hyperintensity in the superolateral portion of Hoffa’s fat pad, accompanied by patellar lateral deviation and high patella indicating malalignment), the most likely diagnosis is Hoffa’s Fat Pad Impingement (Patellofemoral Friction Syndrome).
1. Conservative Treatment:
(1) Relieve local inflammation and pain: Under the guidance of a physician, non-steroidal anti-inflammatory drugs (NSAIDs) or local physical therapy (such as ice packs, ultrasound, or low-frequency therapy) can be employed.
(2) Strengthen surrounding knee joint musculature: Emphasize the medial portion of the quadriceps (especially the vastus medialis oblique, VMO). Appropriate isometric contractions and low-load closed-chain exercises can improve patellar stability and reduce continuous impingement on Hoffa’s fat pad.
(3) Correct lower limb alignment: If necessary, consult a rehabilitation specialist or orthopedic physician for orthotic insoles or knee braces to minimize patellofemoral malalignment.
2. Indications for Surgical Intervention:
If conservative treatment shows no substantial improvement and pain persists or significant functional impairment occurs, arthroscopic exploration and debridement may be considered. This includes removing inflammatory hyperplastic tissues in the fat pad and correcting patellofemoral alignment imbalances (e.g., appropriate soft tissue release, lateral retinaculum release, etc.).
3. Rehabilitation/Exercise Prescription (FITT-VP Principle) Example:
(1) Frequency (F): 3–4 sessions per week focusing on strengthening the muscles around the knee joint.
(2) Intensity (I): Start with low-load (non-weight-bearing or low-resistance band) closed-chain exercises. Increase resistance progressively as symptoms improve and muscle strength develops.
(3) Time (T): Each session can last 20–30 minutes, adjusted according to tolerance.
(4) Type (T): Emphasize isometric or low-load isotonic quadriceps exercises initially; once local pain is reduced, progress to static squats, partial squats, and other joint stability drills.
(5) Progression (P): Increase exercise difficulty and intensity gradually as knee function and pain improve. For instance, progress from seated leg raises (low resistance) to multi-joint closed-chain weight-bearing exercises, while also strengthening core muscles.
(6) Volume (V): Assess according to the patient’s overall physical condition. Each session may be divided into sets (e.g., 3–4 sets), resting 30–60 seconds between sets to ensure safety and tolerance.
Throughout the rehabilitation process, regular follow-up is recommended to monitor symptoms and knee stability. Adjust exercise intensity and form under the guidance of medical professionals or rehabilitation therapists. If other lower limb alignment issues or obesity are present, a more individualized approach is necessary to avoid excessive loading and further injury.
This report provides a reference analysis based on the current condition and imaging data and cannot replace in-person clinical consultation or professional medical advice. The actual treatment plan should be formed by professional physicians in conjunction with comprehensive examination, laboratory results, and individual differences.
Patellofemoral friction syndrome.
