With cases from James Noake In musculoskeletal medicine, we are trained to recognise patterns. Most of the time, the answer sits comfortably within the familiar: overload, strain, tendinopathy. But every so often, something doesn’t quite fit. The story is slightly off, the response to treatment unexpected, or the clinical picture just a little too inconsistent. This is where the ‘Zebra Farm’ comes in. Each time, we explore a trio of real-world cases as written up by Dr James Noake (Consultant in Musculoskeletal, Sport and Exercise Medicine) in his upcoming book ‘Real World Sports Medicine and Musculoskeletal Case Studies : Knee and Lower Leg’. The cases challenge diagnostic instinct; presentations that look routine on the surface but reveal something far less obvious underneath. These are not just rare conditions for rarity’s sake; they are reminders of the cognitive traps we all fall into: anchoring, pattern recognition bias, and premature closure. Because sometimes, when you hear hoofbeats, it isn’t a horse. This is the Zebra Farm. In musculoskeletal medicine, few diagnoses are more common than patellofemoral pain syndrome (PFPS). Anterior knee pain, stairs, squatting, sitting, running, jumping pain all form a pattern to clinicians. Most of the time, the diagnosis is correct. But, every so often, patients present with what appears to be classic PFPS, only for the real diagnosis to sit somewhere entirely different. Perhaps in connective tissue, instability, or an embryological remnant hidden within the joint itself. This is where the Zebra Farm comes in. Each time, we explore a trio of real-world cases as written up by Dr James Noake (Consultant in Musculoskeletal, Sport and Exercise Medicine) in his upcoming book Real World Sports Medicine and Musculoskeletal Case Studies: Knee and Lower Leg. These cases remind us that not all anterior knee pain is created equal, and that pattern recognition can sometimes become pattern misrecognition. Because sometimes when you hear hoofbeats, it isn’t a horse. This is the Zebra Farm. Case 1: The Patellofemoral Pain That Was Actually hEDS and POTS An ex-ice skater, now into weight training, presented with: * Bilateral anterior knee pain * Generalised fatigue * Postural dizziness * Occasional palpitations At first glance, the knee symptoms looked like entirely plausible patellofemoral pain syndrome in a young athletic individual. However, the clue wasn’t in the knees - it was in everything else. The patient described: * Light-headedness on standing * Fatigue disproportionate to activity * Palpitations * Generalised hypermobility Increasing the chance that this is a systems issue, rather than an isolated knee injury. Diagnosis: Hypermobile Ehlers-Danlos Syndrome (hEDS) with Postural Orthostatic Tachycardia Syndrome (POTS) The anterior knee pain was merely one manifestation of a broader connective tissue disorder. The patient required multidisciplinary assessment including cardiac evaluation and investigation for POTS, which is strongly associated with hypermobility and Ehlers-Danlos Syndrome. Why It Fooled Clinicians * The presenting complaint was knee pain * Many patients with hypermobility are highly active athletes or dancers * The autonomic symptoms may be volunteered only when specifically asked Key Sign ➡️ Anterior knee pain accompanied by fatigue, dizziness, palpitations or widespread musculoskeletal complaints should prompt consideration of a systemic cause. Clinical Pearl As performing arts Physiotherapist Liz Bayley notes in her accompanying reflection: “Dancers, gymnasts, circus artists, divers, and skaters occupy a space where artistry and athleticism are inseparable, and where hypermobility is not only common, but actively celebrated. In these populations, hypermobility spectrum disorders (HSDs) and Ehlers-Danlos Syndrome (EDS) appear with notable frequency. It is not difficult to understand why. Children who are naturally “bendy” find themselves in environments where those qualities are rewarded - praised for party tricks, admired for high kicks and deep backbends, selected for their aesthetically pleasing lines, their pliable feet, their effortless turnout. What begins as a biological variation becomes, over time, a professional asset. And yet, the demands placed on these bodies have evolved. Dance in 2026 is no longer defined solely by artistry; it is increasingly virtuosic and relentlessly athletic. Choreography now requires strength, power, stamina, coordination, and precision at the highest level. Hypermobility challenges the traditional biomedical model - for those working with dancers and aesthetic athletes, it also requires navigating the tension between performance demands and physiological reality. Ultimately, while hypermobility may complicate clinical pathways, it also offers an opportunity to practice with greater curiosity, compassion, and depth. Being flexible goes both ways.” Sometimes the Problem Isn’t Pain... It’s Instability The first case reminds us that anterior knee pain can be part of a multisystem disorder. The next case appears far more mechanical. But what looks like patellofemoral pain is actually the aftermath of a major instability event. Case 2: The Patellofemoral Pain That Was Actually a Patellar Dislocation [pg 144 - inc MRI and USS images] A tall, hypermobile woman in her twenties landed awkwardly from a jump for a ball. The mechanism: * Single-leg landing * Dynamic valgus collapse * Immediate severe pain * Inability to weight bear Initial Thoughts Many clinicians seeing the patient later in her recovery might simply encounter: * Anterior knee pain * Retropatellar discomfort * Effusion * Quadriceps inhibition * Apprehension during loading Which can be features of patellofemoral pain. The Role of Imaging MRI demonstrated: * Patellofemoral dislocation * Medial patellofemoral ligament (MPFL) tear * Large haemarthrosis * Relatively shallow trochlear groove Ultrasound additionally demonstrated acute MPFL avulsion injury at the medial patellar border. Diagnosis: Acute Patellofemoral Dislocation with MPFL Tear The patella had physically escaped the trochlear groove, damaging the primary soft-tissue restraint that prevents lateral translation and resulting in structural instability. Why It Fooled Clinicians * Patients may not appreciate that a dislocation actually occurred * The patella often spontaneously relocates * Later presentations may resemble standard anterior knee pain * Quadriceps inhibition is frequently attributed to PFPS Key Sign ➡️ A valgus landing mechanism with immediate swelling, severe pain and inability to weight bear should trigger suspicion of transient patellar dislocation. Extra Zebra? One particularly important pearl from this case: Approximately 50% of acute patellar dislocations may have an associated MCL injury - make sure to assess this too. Could it be the cartilage? The first case was systemic, the second, instability. The third teaches an equally important lesson: sometimes the patellofemoral joint hurts despite the cartilage being completely normal. Case 3: The ‘Chondral Injury’ That Was Actually Medial Plica Syndrome A female weightlifter presented with: * Functionally disabling anterior and medial knee pain * Both retro and suprapatellar pain * Heat and redness (no rheumatology risk factors) * Clicking and catching sensations * Difficulty squatting even with low load * Symptoms during deep snatch positions Many clinicians would immediately think: * Patellofemoral pain syndrome * Chondral injury * Early patellofemoral osteoarthritis …and the history certainly seemed to support it. Clinical Findings Examination demonstrated: * Positive ‘stutter’ test * Positive Clarke’s test * Medial parapatellar pouch tenderness * Low-grade effusion * Mechanical clicking symptoms So far, so cartilaginous. The Imaging MRI showed: * Pristine patellofemoral cartilage surfaces A combination of MRI and ultrasound demonstrated: * A large inflamed serpiginous medial plica * Mechanical impingement during knee movement * Dynamic reproduction of the patient’s clicking symptoms Diagnosis: Medial Plica Syndrome The culprit wasn’t damaged cartilage at all, it was an inflamed embryological remnant mechanically impinging inside an otherwise healthy joint. Why It Fooled Clinicians * Symptoms closely mimicked patellofemoral chondral pain * Clicking reinforced assumptions about cartilage injury * The location of pain was classically retropatellar * Many clinicians are unfamiliar with dynamic ultrasound assessment of the plica Key Sign ➡️ Mechanical anterior knee pain with a normal patellofemoral joint on imaging should prompt consideration of symptomatic plica syndrome. Reality Check James writes that: ‘Plicae are normal anatomical variants and are often overdiagnosed, but occasionally become genuine pain sources, capable of mimicking mechanical patellofemoral pathology.’ Closing Reflection: Patellofemoral Pain Is a Symptom, Not a Diagnosis These three cases look completely different. One is systemic, one instability-related, the other intra-articular soft tissue impingement, yet all three could easily be labelled ‘patellofemoral pain’. Patellofemoral pain syndrome should often be viewed as a working hypothesis rather than a final diagnosis. Across all three cases: * The pain was anterior * The symptoms worsened with loading * The initial pattern appeared familiar * The real diagnosis only emerged after deeper questioning or better imaging The challenge is not necessarily spotting zebras, but in recognising when the horse no longer behaves like a horse. Practical Takeaways When anterior knee pain deserves a second thought * Bilateral symptoms with systemic complaints * Palpitations, dizziness or excessive fatigue - or multiple body systems appear involved * Significant hypermobility * Recurrent instability episodes * Sudden traumatic valgus landing mechanism * Mechanical
