: Lower Extremities
Comprehensive OMT reference hub, interactive cheat sheets, and board review notes for COMLEX Level 1, 2-CE, and 3.
Key Takeaway
Understand Q-angle and hip rules: Coxa vara (<120°) leads to genu valgum and increased Q-angle. Inversion ankle sprains tear the ATFL first and pull the distal fibula anteriorly, locking the proximal fibular head POSTERIORLY. Master knee instability testing (Lachman, Drawer, McMurray).
1. Hip & Pelvis Biomechanics (Angle of Inclination & Q-Angle)
The hip joint transfers weight from the pelvis to the lower extremity. Mechanical alignment is evaluated using the Angle of Inclination and Q-Angle.
| Structural Parameter | Normal Range | Deformity & Pathological Alignment | Associated Clinical Syndrome |
|---|---|---|---|
| Angle of Inclination (Femoral Neck/Shaft) | 120° – 135° | Coxa Valga (> 135°) $\rightarrow$ Genu Varum ('Bow-legged') Coxa Vara (< 120°) $\rightarrow$ Genu Valgum ('Knock-kneed') | Altered gait biomechanics; increased hip osteoarthritis risk. |
| Q-Angle (ASIS to Patella vs. Tibial Tuberosity) | 10°–12° (Men) 15°–18° (Women) | Increased Q-Angle (associated with Coxa Vara & Genu Valgum) | Patellofemoral Pain Syndrome; lateral patellar subluxation. |
2. Knee Ligament & Meniscal Diagnostic Matrix
| Knee Structure | Primary Function | Diagnostic Clinical Test | Key Exam Finding |
|---|---|---|---|
| Anterior Cruciate Ligament (ACL) | Prevents anterior tibial translation | Lachman Test (most sensitive) & Anterior Drawer | Soft end-point; anterior movement of tibia > 5mm. |
| Posterior Cruciate Ligament (PCL) | Prevents posterior tibial translation | Posterior Drawer & Posterior Sag Sign | Posterior sag of proximal tibia at 90° flexion. |
| Medial Collateral Ligament (MCL) | Resists valgus stress | Valgus Stress Test (at 30° flexion) | Medial joint laxity; pain. |
| Lateral Collateral Ligament (LCL) | Resists varus stress | Varus Stress Test (at 30° flexion) | Lateral joint laxity; pain. |
| Menisci (Medial & Lateral) | Shock absorption & joint stability | McMurray Test & Apley Compression Test | Painful click/pop during rotation with flexion/extension. |
O'Donoghue Unhappy Triad
The Unhappy Triad: Result of severe valgus blow to the lateral knee while the foot is planted. Injures ACL, MCL, and Medial Meniscus (though modern biomechanics notes lateral meniscus is frequently co-injured).
3. Fibular Head Mechanics & Inversion Ankle Sprain
Proximal fibular head motion is directly coupled to distal fibular and ankle movement.
| Ankle / Foot Motion | Distal Fibula Motion | Proximal Fibular Head Motion | Associated Somatic Dysfunction |
|---|---|---|---|
| Ankle Eversion & Dorsiflexion | Posterior Glide | ANTERIOR Glide | Anterior Fibular Head (resists posterior glide). |
| Ankle Inversion & Plantarflexion | Anterior Glide | POSTERIOR Glide | Posterior Fibular Head (resists anterior glide). |
INVERSION ANKLE SPRAIN CHAIN REACTION: 1. Mechanism: Inversion + Plantarflexion. 2. Ligament Tear Order: - 1st: Anterior Talofibular Ligament (ATFL) ('Always Tear First Ligament'). - 2nd: Calcaneofibular Ligament (CFL). - 3rd: Posterior Talofibular Ligament (PTFL). 3. Fibular Coupling: Distal fibula pulled anteriorly $\rightarrow$ Proximal fibular head glides POSTERIORLY!
4. Foot Arches & Key Somatic Dysfunctions
| Foot Arch | Keystone Bone | Common Dysfunction | OMT Correction Technique |
|---|---|---|---|
| Medial Longitudinal Arch | Navicular | Navicular drop (Pes Planus / Flat feet) | Navicular BLT / HVLA mobilization. |
| Lateral Longitudinal Arch | Cuboid | Dropped Cuboid (Plantar subluxation) | Hiss Whip technique / Cuboid springing. |
| Transverse Arch | Cuneiforms (Medial, Intermed, Lat) | Flattened arch / Plantar cuneiform | Transverse arch compression/springing. |
5. COMLEX Practice Knowledge Check
Source
Based on the publicly available table of contents and topic organization of OMM Review: A Comprehensive Review of Osteopathic Medicine. All notes are original; no copyrighted text, figures, or full source material is included.