Patellofemoral Pain Syndrome (Runner's Knee)

**Patellofemoral pain syndrome (PFPS)** is anterior knee pain caused by dysfunction of the **patellofemoral joint** — where the kneecap (patella) glides in the trochlear groove of the femur. The pain doesn't come from a single specific structure but rather from abnormal stress on the joint due to: - **Maltracking** of the patella in the trochlear groove - **Cartilage stress** on the back of the patella - **Abnormal forces** during knee flexion-extension - **Soft tissue irritation** of surrounding structures **Key Anatomical Concepts:** **The Q Angle:** - The angle formed by the line of pull of the quadriceps and the patellar tendon - Wider in women due to broader pelvis (~15-20° vs 10-15° in men) - Higher Q angle = more lateral pull on the patella = increased PFPS risk **Patellar Tracking:** - The patella should glide centrally in the trochlear groove during knee flexion - Excessive lateral tracking is the hallmark of PFPS - Influenced by quadriceps balance, hip mechanics, and foot pronation **The Kinetic Chain:** - PFPS is rarely just a "knee problem" - **Hip weakness** (especially gluteus medius) allows hip drop during running - Hip drop causes **knee valgus** (knee caves inward) - Knee valgus increases lateral patellar pressure - Foot pronation also contributes to abnormal lower limb mechanics **Conditions on the Spectrum:** - **Chondromalacia patellae** — actual cartilage softening (more severe form) - **PFPS** — the broader umbrella term, often without clear cartilage changes - **Patellar tendinopathy ("jumper's knee")** — affects the tendon below the patella, distinct condition

## Root Causes **Patellofemoral pain is rarely from a single cause — it's typically a combination of factors:** **1. Hip Weakness (Most Important — Present in 80-90% of cases):** - **Gluteus medius weakness** — allows hip drop during weight-bearing - **Gluteus maximus weakness** — reduces stabilization of the femur - Hip weakness leads to dynamic knee valgus (knee caves inward) - Knee valgus dramatically increases lateral patellar pressure **2. Quadriceps Imbalances:** - **Vastus medialis oblique (VMO) weakness or delayed activation** - The VMO normally pulls the patella medially during contraction - Weak VMO allows lateral patellar tracking - **Vastus lateralis dominance** worsens lateral pulling **3. Tight Soft Tissues:** - **Iliotibial band tightness** — pulls the patella laterally - **Lateral retinaculum tightness** — restricts medial patellar movement - **Hamstring tightness** — increases knee flexion forces - **Calf tightness** — alters lower limb biomechanics **4. Foot/Ankle Mechanics:** - **Excessive pronation (flat feet)** — internally rotates the tibia - Tibial internal rotation increases the Q angle - Higher Q angle = more lateral patellar pressure **5. Training Errors:** - Sudden increase in running volume (>10% per week) - Adding hill running too quickly - Inadequate rest between training sessions - Training on cambered or hilly surfaces **6. Anatomic Factors:** - High Q angle (women particularly) - Patella alta (high-riding patella) - Trochlear dysplasia (shallow trochlear groove) - Genu valgum (knock knees) **Risk Factors:** - Female sex (2x risk) - Adolescents and young adults (peak ages 15-30) - Running, cycling, basketball, volleyball - Sudden increase in activity level - Weak hip musculature - Flat feet or excessive foot pronation - Wide hips (higher Q angle)

## Conservative Treatment (First-Line — 70-90% Success) **1. Hip Strengthening (THE MOST IMPORTANT INTERVENTION):** This is the cornerstone of PFPS treatment. Hip-focused programs outperform knee-only programs by significant margins. *Key Hip Exercises (3 sets of 15, 3x weekly):* - **Clamshells** — side-lying with knees bent, lift top knee - **Side-lying leg raises** — strengthens gluteus medius - **Single-leg bridges** — gluteus maximus activation - **Monster walks with band** — hip abduction with resistance - **Sidesteps with band** — gluteus medius endurance - **Single-leg squats** — functional strengthening (start at small range, progress) **2. Quadriceps Strengthening (Pain-Free Range):** - **Closed-chain exercises preferred** (squats, lunges) over open-chain (leg extensions) — less patellofemoral stress - Start with mini-squats (45° flexion) and progress depth as tolerated - Wall sits — isometric quad strengthening - Step-ups — functional knee strengthening - Avoid deep squats and full leg extensions during acute phase **3. Stretching Program:** - **ITB stretching** — standing cross-legged stretch, foam rolling - **Hamstring stretching** — supine straight-leg raise - **Hip flexor stretching** — kneeling lunge stretch - **Calf stretching** — wall stretch, both straight and bent knee - Hold 30 seconds, 3 reps, 3x daily **4. Activity Modification:** - Reduce running volume by 50% temporarily - Substitute swimming, elliptical, or cycling (often well-tolerated) - Avoid stairs when possible during acute pain - Use a soft seat cushion for prolonged sitting **5. Patellar Taping or Bracing:** - McConnell taping — holds patella medially during activity - Patellar stabilization braces — provide proprioceptive feedback - May allow earlier return to activity during rehabilitation - Should be combined with strengthening, not as standalone treatment **6. Foot Orthotics (For Overpronation):** - Prefabricated arch supports often sufficient - Custom orthotics for severe overpronation - Reduces tibial internal rotation - Particularly helpful in 30-40% of PFPS patients **7. Pain Management:** - NSAIDs for 2-4 weeks during acute flares - Ice 15-20 minutes after activity - Compression sleeves for symptomatic relief ## What Doesn't Work as Well - **Isolated quadriceps strengthening** without hip work - **Prolonged rest** — leads to deconditioning, often makes symptoms worse - **Corticosteroid injection** — limited evidence; NOT recommended for PFPS - **Surgery** — rarely indicated; <5% of cases ## Surgical Treatment (<5% of Cases) Reserved for refractory cases with specific anatomic abnormalities: - **Lateral retinacular release** — for tight lateral structures - **Tibial tubercle transfer** — for severe maltracking - **Trochleoplasty** — for severe trochlear dysplasia - Surgery success rates lower than for other knee conditions; should only be considered after 6+ months of structured rehabilitation