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The Zebra Farm: When Anterior Knee Pain Isn’t Patellofemoral Pain · MSKMag OutLoud

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  SPEAKER_00: Zebra Farm, when patellofemoral pain isn't just patellofemoral pain.
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  SPEAKER_00: Written by James Noak.
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  SPEAKER_00: In musculoskeletal medicine,
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  SPEAKER_00: a few diagnoses are more common than patellofemoral pain syndrome, PFPS.
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  SPEAKER_00: Anterior knee pain, stairs,
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  SPEAKER_00: squatting, sitting, running, jumping, pain, all form a pattern to clinicians.
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  SPEAKER_00: Most of the time, the diagnosis is correct.
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  SPEAKER_00: But every so often patients present with what appears to be classic PFPS only for
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  SPEAKER_00: the real diagnosis to sit somewhere entirely different.
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  SPEAKER_00: Perhaps in connective tissue,
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  SPEAKER_00: instability or an embryological remnant hidden within the joint itself.
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  SPEAKER_00: This is where the zebra farm comes in.
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  SPEAKER_00: Each time we explore a trio of real-world cases as written up by Dr.
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  SPEAKER_00: James Noak,
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  SPEAKER_00: consultant in Musculoskeletal Sport and Exercise Medicine,
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  SPEAKER_00: in his upcoming book,
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  SPEAKER_00: Real World Sports Medicine and Musculoskeletal Case Studies, Knee and Lower Leg.
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  SPEAKER_00: These cases remind us that not all anterior knee pain is created equal,
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  SPEAKER_00: and that pattern recognition can sometimes become pattern misrecognition.
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  SPEAKER_00: Because sometimes when you hear hoof beats, it isn't a horse.
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  SPEAKER_00: This is the zebra farm.
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  SPEAKER_00: Case one,
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  SPEAKER_00: the patellofemoral pain that was actually hypermobile,
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  SPEAKER_00: Ehlers-Danlos syndrome and POTS.
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  SPEAKER_00: An ex ice skater now into weight training presented
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  SPEAKER_00: with bilateral anterior knee pain,
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  SPEAKER_00: generalized fatigue, postural dizziness, occasional palpitations.
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  SPEAKER_00: At first glance,
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  SPEAKER_00: the knee symptoms looked like an entirely plausible patellofemoral pain syndrome in
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  SPEAKER_00: a young athletic individual.
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  SPEAKER_00: However, the clue wasn't in the knees, it was in everything else.
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  SPEAKER_00: The patient described lightheadedness on standing,
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  SPEAKER_00: fatigue disproportionate to activity, palpitations, generalized hypermobility.
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  SPEAKER_00: Increasing the chance that this is a systems issue rather than an isolated knee injury.
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  SPEAKER_00: Diagnosis, Hypermobile Ehlers-Danlos Syndrome with Postural Orthostatic Tachycardia Syndrome .
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  SPEAKER_00: The anterior knee pain was merely one manifestation of a broader connective tissue disorder.
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  SPEAKER_00: The patient required multidisciplinary assessment including cardiac evaluation
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  SPEAKER_00: and investigation for POTS which is strongly associated with hypermobility
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  SPEAKER_00: and Ehlers-Danlos Syndrome.
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  SPEAKER_00: Why if fooled conditions?
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  SPEAKER_00: The presenting complaint was knee pain.
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  SPEAKER_00: Many patients with hypermobility are highly active athletes or dancers.
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  SPEAKER_00: The autonomic symptoms may be volunteered only when specifically asked.
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  SPEAKER_00: Anterior knee pain accompanied by fatigue,
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  SPEAKER_00: dizziness,
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  SPEAKER_00: palpitations,
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  SPEAKER_00: or widespread musculoskeletal complaints should prompt consideration of
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  SPEAKER_00: a systemic cause.
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  SPEAKER_00: Clinical Pearl.
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  SPEAKER_00: As performing arts physiotherapist Liz Bailey notes in her accompanying reflection,
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  SPEAKER_00: dancers,
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  SPEAKER_00: gymnasts,
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  SPEAKER_00: circus artists, divers,
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  SPEAKER_00: and skaters occupy a space where artistry and athleticism are inseparable and
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  SPEAKER_00: where hypermobility is not only common but actively celebrated.
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  SPEAKER_00: In these populations,
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  SPEAKER_00: hypermobility spectrum disorders and Ehlers-Danlos syndrome appear
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  SPEAKER_00: with notable frequency.
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  SPEAKER_00: It is not difficult to understand why.
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  SPEAKER_00: Children who are naturally bendy find themselves in environments
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  SPEAKER_00: where those qualities are rewarded,
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  SPEAKER_00: praised for party tricks,
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  SPEAKER_00: admired for high kicks and deep backbends,
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  SPEAKER_00: selected for their aesthetically pleasing lines,
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  SPEAKER_00: their pliable feet, their effortless turnout.
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  SPEAKER_00: What begins as biological variation becomes over time a professional asset.
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  SPEAKER_00: And yet, the demands placed on these bodies have evolved.
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  SPEAKER_00: Dance in 2026 is no longer defined solely by artistry.
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  SPEAKER_00: It is increasingly virtuosic and relentlessly athletic.
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  SPEAKER_00: Choreography now requires strength,
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  SPEAKER_00: power, stamina, coordination, and precision at the highest level.
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  SPEAKER_00: Hypermobility challenges the traditional biomedical model.
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  SPEAKER_00: For those working with dance and aesthetic athletes,
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  SPEAKER_00: it also requires navigating the tension between performance demands
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  SPEAKER_00: and physiological reality.
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  SPEAKER_00: Ultimately,
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  SPEAKER_00: while hypermobility may complicate clinical pathways,
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  SPEAKER_00: it also offers an opportunity to practice with greater curiosity,
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  SPEAKER_00: compassion and depth.
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  SPEAKER_00: Being flexible goes both ways.
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  SPEAKER_00: Sometimes the problem isn't pain, it's instability.
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  SPEAKER_00: The first case reminds us that anterior knee pain can be part of a multi-system disorder.
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  SPEAKER_00: The next case appears far more mechanical.
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  SPEAKER_00: But what looks like patellofemoral pain is actually the aftermath of a major instability event.
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  SPEAKER_00: Case 2.
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  SPEAKER_00: The patellofemoral pain that was actually a patellar dislocation.
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  SPEAKER_00: A tall, hypermobile woman in her 20s landed awkwardly from a jump for a ball.
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  SPEAKER_00: The mechanism.
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  SPEAKER_00: Single leg landing, dynamic valgus collapse, immediate severe pain, inability to weight bear.
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  SPEAKER_00: Initial thoughts.
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  SPEAKER_00: Many clinicians seeing the patient later
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  SPEAKER_00: in their recovery might simply encounter anterior knee pain,
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  SPEAKER_00: retropatellar discomfort,
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  SPEAKER_00: effusion,
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  SPEAKER_00: quadriceps inhibition,
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  SPEAKER_00: apprehension during loading, which can be features of patellofemoral pain.
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  SPEAKER_00: The role of imaging.
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  SPEAKER_00: Memori demonstrated patellofemoral dislocation,
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  SPEAKER_00: medial patellofemoral ligament,
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  SPEAKER_00: MPFL tear, large haemarthrosis, relatively shallow trochlear groove.
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  SPEAKER_00: Ultrasound additionally demonstrated acute MPFL avulsion injury at the medial patellar border.
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  SPEAKER_00: Acute patellofemoral dislocation with MPFL tear.
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  SPEAKER_00: The patella had physically escaped the trochlear groove,
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  SPEAKER_00: damaging the primary soft tissue restraint that prevents lateral translation
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  SPEAKER_00: and resulting in structural instability.
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  SPEAKER_00: Why it fooled clinicians?
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  SPEAKER_00: Patients may not appreciate that a dislocation actually occurred.
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  SPEAKER_00: The patella often spontaneously relocates.
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  SPEAKER_00: Later presentations may resemble standard anterior knee pain.
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  SPEAKER_00: Quadriceps inhibition is frequently attributed to PFPS.
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  SPEAKER_00: A valgus landing mechanism with immediate swelling,
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  SPEAKER_00: severe pain,
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  SPEAKER_00: and inability to weight bear should trigger suspicion
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  SPEAKER_00: of transient patellar dislocation.
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  SPEAKER_00: Extra Zebra.
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  SPEAKER_00: One particularly important pearl from this case,
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  SPEAKER_00: approximately 50% of acute patellar dislocations may have an associated MCL injury.
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  SPEAKER_00: Make sure to assess this too.
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  SPEAKER_00: Could it be the cartilage?
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  SPEAKER_00: The first case was systemic, the second instability.
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  SPEAKER_00: The third teaches an equally important lesson.
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  SPEAKER_00: Sometimes the patellofemoral joint hurts despite the cartilage being completely normal.
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  SPEAKER_00: Case three, the chondral injury that was actually medial plica syndrome.
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  SPEAKER_00: A female weightlifter presented with functionally disabling anterior
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  SPEAKER_00: and medial knee pain,
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  SPEAKER_00: both retro and suprapatellar pain,
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  SPEAKER_00: heat and redness,
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  SPEAKER_00: but no rheumatology risk factors,
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  SPEAKER_00: clicking and catching sensations,
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  SPEAKER_00: difficulty squatting even with low load, symptoms during deep snatch positions.
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  SPEAKER_00: Many clinicians would immediately think,
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  SPEAKER_00: patellofemoral pain syndrome,
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  SPEAKER_00: chondral injury,
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  SPEAKER_00: early patellofemoral osteoarthritis, and the history certainly seemed to support it.
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  SPEAKER_00: Clinical findings,
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  SPEAKER_00: examination demonstrated,
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  SPEAKER_00: positive stutter test,
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  SPEAKER_00: positive Clark's test,
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  SPEAKER_00: medial parapatellar pouch tenderness,
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  SPEAKER_00: low-grade effusion, mechanical clicking symptoms.
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  SPEAKER_00: So far, so cartilaginous.
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  SPEAKER_00: MRI showed pristine patellofemoral cartilage surfaces.
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  SPEAKER_00: A combination of MRI and ultrasound demonstrated a large inflamed serpiginous medial plica
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  SPEAKER_00: Serpiginous.
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  SPEAKER_00: Mechanical impingement during knee movement.
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  SPEAKER_00: A dynamic reproduction of the patient's clicking symptoms.
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  SPEAKER_00: Diagnosis.
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  SPEAKER_00: Medial plica syndrome.
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  SPEAKER_00: The culprit wasn't damaged cartilage at all.
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  SPEAKER_00: It was an inflamed embryological remnant mechanically impinging inside
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  SPEAKER_00: an otherwise healthy joint.
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  SPEAKER_00: Why it fooled clinicians.
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  SPEAKER_00: Symptoms closely mimicked patellofemoral chondral pain.
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  SPEAKER_00: Clicking reinforced assumptions about cartilage injury.
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  SPEAKER_00: The location of pain was classically retropatellar.
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  SPEAKER_00: Many clinicians are unfamiliar with dynamic ultrasound assessment of the plica.
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  SPEAKER_00: Key sign,
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  SPEAKER_00: mechanical anterior knee pain with a normal patellofemoral joint
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  SPEAKER_00: on imaging should prompt consideration of symptomatic plica syndrome.
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  SPEAKER_00: Reality check.
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  SPEAKER_00: James writes that
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  SPEAKER_00: plicae
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  SPEAKER_00: are normal anatomical variants and are often diagnosed
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  SPEAKER_00: but occasionally become genuine pain sources capable
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  SPEAKER_00: of mimicking mechanical patellofemoral pathology.
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  SPEAKER_00: Closing reflection, patellofemoral pain is a symptom, not a diagnosis.
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  SPEAKER_00: These three cases look completely different.
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  SPEAKER_00: One is systemic,
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  SPEAKER_00: one instability related,
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  SPEAKER_00: the other intra-articular soft tissue impingement,
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  SPEAKER_00: yet all three of them could easily be labeled patellofemoral pain.
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  SPEAKER_00: Patellofemoral pain syndrome should be viewed as a working hypothesis rather than
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  SPEAKER_00: a final diagnosis.
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  SPEAKER_00: Across all three cases the pain was anterior,
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  SPEAKER_00: the symptoms worsened with loading,
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  SPEAKER_00: the initial pattern appeared familiar,
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  SPEAKER_00: the real diagnosis only emerged after deeper questioning or better imaging.
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  SPEAKER_00: The challenge is not necessarily spotting zebras but in recognising when
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  SPEAKER_00: the horse no longer behaves like a horse.
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  SPEAKER_00: Practical takeaways.
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  SPEAKER_00: When anterior knee pain deserves a second thought.
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  SPEAKER_00: Bilateral symptoms with systemic complaints.
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  SPEAKER_00: Palpitations, dizziness or excessive fatigue or multiple body systems appear involved.
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  SPEAKER_00: Significant hypermobility.
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  SPEAKER_00: Recurrent instability episodes.
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  SPEAKER_00: Sudden traumatic valgus landing mechanism.
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  SPEAKER_00: Mechanical clicking despite normal cartilage imaging.
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  SPEAKER_00: Failure of otherwise appropriate rehabilitation.
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  SPEAKER_00: Standard treatment repeatedly fails.
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  SPEAKER_00: Alternative diagnoses worth considering.
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  SPEAKER_00: Systemic, Hypermobility Spectrum Disorders, Hypermobile EDS, POTS.
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  SPEAKER_00: Instability,
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  SPEAKER_00: Patellar Dislocation,
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  SPEAKER_00: MPFL Injury,
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  SPEAKER_00: Intraarticular Soft Tissue,
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  SPEAKER_00: Symptomatic Medial Plyca, Structural, Osteochondral Injury, Dysplasia, Malalignment.
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  SPEAKER_00: In musculoskeletal medicine, anterior knee pain is usually just patellofemoral pain.
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  SPEAKER_00: But every so often, it's a zebra!