What risk factors predispose a professional female footballer with a three‑day knee effusion and MRI‑confirmed patellar chondromalacia to this cartilage injury?

Risk Factors for Patellar Chondromalacia in Professional Female Footballers

Female sex, high training loads, low energy availability, and inadequate calcium/magnesium intake are the primary modifiable risk factors for patellar cartilage injury in elite football players.

Sex-Specific Risk Factors

• Female athletes face inherently higher risk for cartilage pathology compared to male counterparts, with approximately 16% body fat mass typical in elite female footballers, though performance can occur outside this range 1
• Women are at increased risk for relative energy deficiency in sport (RED-S), with 26-33% of NCAA Division I female footballers meeting criteria for low energy availability during competitive seasons 1
• Low energy availability directly increases bone and cartilage injury rates by 4.5-fold, affecting both males and females, though females show higher prevalence 1

Training Load and Biomechanical Factors

• High physical demands of elite football create repetitive patellofemoral stress, particularly during preseason when training loads peak and energy intake may be restricted 1
• Bone marrow lesions (BMLs) underlying cartilage are associated with increased knee pain, especially in patients with family history of osteoarthritis 1
• Patellofemoral cartilage loss correlates with chronic knee pain, with active pain linked to underlying BMLs 1

Nutritional Deficiencies as Critical Risk Factors

• Inadequate calcium intake is particularly concerning for athletes training in any environment, as dermal sweat losses and urinary losses deplete calcium stores 1
• The recommended dietary allowance is 700-1000 mg/day; typical sources include milk (240 mg per 200 mL), hard cheese (220 mg per 30 g), and yogurt (200 mg per 120 g) 1
• Magnesium deficiency affects 22% of Olympic athletes at some point, with athletes having history of patella tendon pain showing significantly lower magnesium levels 1
• Magnesium plays essential roles in energy production, muscle function, bone health, and pain modulation—all relevant to cartilage integrity 1

Energy Availability and Body Composition Management

• Restricting carbohydrate intake (e.g., "training low" strategies) increases immunosuppressive stress hormone responses and may compromise tissue healing 1
• Protein intakes below 1.2 g/kg body mass/day impair optimal immune function and tissue repair 1
• 8-9% of female footballers report stress fractures, with 19% experiencing menstrual dysfunction—both markers of low energy availability that predispose to cartilage injury 1

Environmental and Seasonal Stressors

• Heat exposure during training or competition exacerbates cardiovascular and metabolic strain, increasing sweat losses and potentially depleting calcium through dermal losses 1
• Preseason training periods carry highest risk due to combination of increased training load and potential energy restriction for body composition goals 1
• Mid-season fixture congestion increases illness risk and may compromise recovery, indirectly affecting cartilage health 1

Age and Baseline Cartilage Status

• While this patient is young, it is important to note that patients aged 45-55 years show elevated T2 mapping values on 3T MRI even with normal radiographs, suggesting early cartilage degeneration 1
• In younger athletes, acute cartilage injury (as seen here with surface delamination) likely reflects acute trauma superimposed on predisposing factors rather than degenerative disease 1

Critical Pitfalls to Avoid

• Do not dismiss the 3-day effusion as trivial—moderate joint effusion with underlying bone marrow edema (as noted on this MRI) indicates significant intra-articular pathology requiring intervention 1, 2
• Do not overlook nutritional assessment in female athletes presenting with cartilage or bone injuries, as 24% of female Norwegian national team players had disordered eating 1
• Do not assume adequate energy intake based on appearance alone; formal assessment of energy availability should be performed given the 26-33% prevalence of low EA in competitive female footballers 1
• Screen for RED-S components: menstrual dysfunction, stress fracture history, and eating disorder risk should be evaluated in any female athlete with cartilage injury 1

Immediate Clinical Actions

• Assess dietary calcium and magnesium intake using food frequency questionnaire; supplement if intake falls below 700 mg/day calcium 1
• Calculate energy availability by comparing reported energy intake to training expenditure; refer to sports dietitian if EA <30 kcal/kg fat-free mass/day 1
• Evaluate for Female Athlete Triad components (low energy availability, menstrual dysfunction, low bone mineral density) using risk stratification tools 1
• Modify training load during acute phase while ensuring adequate protein (≥1.2 g/kg/day) and carbohydrate intake to support cartilage healing 1