Fat Pad Syndrome (Hoffa's)

Lower Limb

Overview

Hoffa's fat pad syndrome is an inflammatory condition affecting the infrapatellar fat pad located beneath the patellar tendon in the knee joint. This highly innervated and vascularised structure becomes irritated, impinged, or inflamed, causing anterior knee pain that is often exacerbated by extension activities. The condition is commonly seen in athletes and individuals with patellofemoral dysfunction or recent knee trauma.

Pathophysiology

The infrapatellar fat pad (ligamentum mucosum) is a highly sensitive structure rich in nociceptors and blood vessels. Repetitive microtrauma, direct compression, sudden hyperextension, or chronic irritation from patellofemoral joint dysfunction can cause the fat pad to become inflamed, hypertrophic, or impinged between the femoral condyle and tibia. Synovitis and inflammatory mediator release perpetuate pain and swelling. Postural dysfunction and quadriceps weakness allow increased anterior knee translation, compressing the fat pad further.

Patient Education

Hoffa's fat pad syndrome typically responds well to activity modification, reducing deep knee bending movements, and addressing underlying biomechanical issues such as quadriceps weakness or altered patellar tracking.

Typical Presentation

Site

Anterior knee, deep to the patellar tendon, often localised to the infrapatellar region just below the patella

Quality

Sharp, catching, or pinching sensation; may describe as deep knee pain rather than surface pain

Intensity

Mild to moderate (4-7/10), variable depending on activity level

Aggravating

Deep knee bending (stairs, squats, lunges), activities requiring knee extension against resistance, kneeling, prolonged sitting with knee bent, activities causing sudden hyperextension

Relieving

Rest, ice application, anti-inflammatory medications, knee extension in relief position, avoiding deep flexion activities

Associated

Mild swelling around infrapatellar region, slight warmth, catching sensation, functional limitation with stairs, difficulty with sports or running, stiffness after rest

Orthopaedic Tests

Test descriptions are written with AI assistance from standard clinical texts. Where a test lists Sources, its description has been checked against them; those sources are independent and do not endorse OsteoKit. Accuracy figures and grades (A–D) appear only when checked against the published study; tests without one are marked “No accuracy study”.

Further reading: full test procedures are described in standard clinical examination texts, e.g. Magee & Manske, Orthopedic Physical Assessment (7th ed.), and Cook & Hegedus, Orthopedic Physical Examination Tests: An Evidence-Based Approach (2nd ed.).

No accuracy study

Hoffa's Test (Fat Pad Impingement Test)

Procedure

Patient supine, knee bent to about 30°. Press your thumbs into the soft tissue either side of the patellar tendon, just below the kneecap, and ask the patient to straighten the knee fully.

Positive Finding

Reproduction of the familiar pain below the kneecap as the knee reaches full extension.

Interpretation

Supports fat pad irritation. Pain on pressing here also occurs with patellar tendinopathy, so a positive result on its own does not separate the two. Not a validated test. Hoffa's test is a provocation manoeuvre for infrapatellar fat pad impingement with no established diagnostic accuracy; the previously cited Ferretti 1992 work concerns patellar tendinopathy (jumper's knee), not the accuracy of this test, so no validated sensitivity/specificity pair supports the figures shown.

Sources

No accuracy study

Fat Pad Palpation (Knee Bent and Straight)

Procedure

Patient supine. Palpate the fat pad either side of the patellar tendon with the knee bent, then with it straight, and compare.

Positive Finding

Tenderness either side of the tendon that is worse with the knee straight.

Interpretation

Fat pad tenderness is typically worse in extension, while patellar tendon tenderness at the lower pole tends to ease when the knee is straight and the tendon is relaxed. This helps separate the two but is not validated.

Sources

No accuracy study

Knee Extension Lag with Fat Pad Palpation

Procedure

Patient supine or seated. Ask the patient to straighten the knee fully, and to push the knee into full extension, while you palpate either side of the patellar tendon.

Positive Finding

Pain under the kneecap at end-range extension or with the knee pushed back into hyperextension.

Interpretation

Pain at end-range or hyperextension fits fat pad irritation, as the fat pad is squeezed in this position. Not a validated test.

Sources

No accuracy study

Joint Effusion Check (Bulge Sign / Patellar Tap)

Procedure

Patient supine, knee straight and relaxed. Stroke up the inner side of the knee, then down the outer side, and watch for a bulge on the inner side. For larger effusions, squeeze the suprapatellar pouch down and press the kneecap onto the femur.

Positive Finding

A bulge of fluid returning on the inner side, or the kneecap tapping on the femur.

Interpretation

A joint effusion points to a problem inside the joint (such as a meniscal or cartilage injury, or synovitis) rather than isolated fat pad irritation, and is a reason for further assessment.

Sources

No accuracy study

Medial-Lateral Fat Pad Discrimination Palpation

Procedure

Patient supine, knee straight and relaxed. Palpate the soft tissue on each side of the patellar tendon, and the tendon itself, from the lower pole of the kneecap down to the tuberosity.

Positive Finding

Tenderness in the soft tissue beside the tendon rather than on the tendon itself.

Interpretation

Tenderness beside the tendon fits fat pad irritation; tenderness on the tendon at the lower pole fits patellar tendinopathy. The two often coexist.

Sources

⚠ Red Flags

  • •Severe acute swelling with inability to bear weight following traumatic injury
  • •Signs of acute ligamentous injury (ACL/MCL/PCL damage)
  • •Fever with joint swelling suggesting septic arthritis
  • •History of cancer with new knee symptoms
  • •Severe redness and warmth suggesting acute infection
  • •Mechanical locking suggestive of meniscal tear

⚡ Yellow Flags

  • •High fear-avoidance behaviours regarding knee movement
  • •Excessive catastrophising about symptoms
  • •Poor compliance with activity modification recommendations
  • •Secondary gain factors related to injury
  • •Significant psychological distress affecting function
  • •Unrealistic expectations for rapid recovery

Osteopathic Techniques

Physical therapy is the mainstay: VMO strengthening, taping to offload the fat pad, stretching, and gluteal and pelvic control work.

Region

Infrapatellar fat pad and anterior knee

Technique

Soft tissue, knee and quadriceps
Grade D
Low evidence: expert consensus or could not be verified against literature
No trials in fat pad syndrome. In a small knee osteoarthritis trial, manual release improved fat pad movement on MRI.

Rationale

Hands-on work to the quadriceps and the tissues around the knee to ease tension and pain.

How it's done & evidence

How it's done

Hands-on kneading, stroking and sustained pressure to the quadriceps, the patellar and quadriceps tendons, the iliotibial band near the knee and the tissues around the joint. Transverse friction massage across a tendon is one form. In trials it was given alongside exercise.

Evidence in Fat Pad Syndrome (Hoffa's)

Searched 24 Oct 2026: no trials in Hoffa fat pad syndrome. Okita 2022 (n=14, knee osteoarthritis): after 12 sessions, the fat pad moved forward more during knee extension with manual release than with stretching. Kitagawa 2022 (n=64, healthy adults): one session of manual therapy did not change fat pad flexibility.

Region

Patellofemoral joint (kneecap glides)

Technique

Articulation, knee (tibiofemoral and patellofemoral)No trials found

Rationale

Gentle, rhythmic glides of the knee and kneecap within their range to ease pain and stiffness.

How it's done, cautions & evidence

How it's done

Passive, low-velocity glides of the knee within its range, with no thrust: distraction and front-to-back glides of the tibia on the femur, and glides of the kneecap in each direction, usually 2–3 oscillations a second for 1–2 minutes. A Mulligan variant holds a sustained glide of the tibia while the patient actively bends and straightens the knee.

Cautions

In knee osteoarthritis trials, no serious adverse events were reported with manual therapy.

Evidence in Fat Pad Syndrome (Hoffa's)

Searched 24 Oct 2026: no trials of patellofemoral mobilisation in fat pad syndrome.

Region

Quadriceps (rectus femoris)

Technique

Muscle energy, hip and thigh musclesNo trials found

Rationale

Low-force, patient-powered stretch for tight hip and thigh muscles.

How it's done, cautions & evidence

How it's done

The muscle (for example the hamstrings, adductors or rectus femoris) is taken to its barrier. The patient pushes gently, at about 10–20% effort, against resistance for 5–10 seconds, relaxes for 3–5 seconds, and the new barrier is taken up.

Cautions

Not used with an acute fracture, a joint infection or a bone malignancy; take care with severe osteoporosis or after surgery that limits muscle contraction. Use the least force needed: too much can tear a muscle or pull off a tendon, especially in older patients.

Evidence in Fat Pad Syndrome (Hoffa's)

Searched 24 Oct 2026: no trials of quadriceps muscle energy technique in fat pad syndrome.

Rehabilitation Exercises

Supine Knee Extension with Towel Roll

Range of MotionBeginner

Quadriceps Stretch (Standing or Prone)

StretchingBeginner

IT Band and Hip Flexor Stretch

StretchingBeginner

Quadriceps Setting (Isometric VMO Contraction)

StrengtheningBeginner

Straight Leg Raise (Supine)

StrengtheningIntermediate

Short Arc Quadriceps Strengthening

StrengtheningIntermediate

Terminal Knee Extension (TKE) with Resistance Band

StrengtheningIntermediate

Step-Ups (Low Height, Progressive)

StrengtheningIntermediate

Single Leg Stance on Stable Surface

BalanceIntermediate

Hip Abduction in Standing (Clamshells or Side-Lying)

PosturalIntermediate

Lateral Lunge (Controlled Depth)

StrengtheningAdvanced

Single Leg Squats or Pistol Squat Progression

BalanceAdvanced

Referral Criteria

  • •Failure to improve after 6-8 weeks of conservative treatment
  • •Signs of meniscal pathology (mechanical locking, giving way)
  • •Suspected ligamentous injury (ACL/MCL/PCL)
  • •Imaging evidence of significant osteoarthritis or loose bodies
  • •Persistent swelling despite treatment
  • •Suspected infection or septic arthritis (fever, severe warmth, redness)
  • •Functional limitation preventing return to work or daily activities
  • •Consideration for injection therapy (corticosteroid injection) or surgical intervention if fat pad impingement confirmed on imaging