OMM Review — Lower Extremities
Original OMM review notes for hip, knee, ankle, and foot mechanics, dysfunction, and entrapments.
Hip and Knee
The hip is a ball-and-socket joint with flexion, extension, abduction, adduction, internal/external rotation, and circumduction. The knee primarily flexes and extends, with a small amount of tibial rotation in flexion.
Tibial torsion and femoral anteversion affect apparent foot progression angle; distinguish structural from functional causes.
Ankle and Foot
Ankle motion is primarily dorsiflexion and plantarflexion at the talocrural joint, with inversion/eversion at the subtalar and transverse tarsal joints. Dysfunction often involves restricted talocrural dorsiflexion due to posterior talar glide restriction.
| Dysfunction | Common findings |
|---|---|
| Anterior innominate rotation | ASIS low, functional leg appears long |
| Posterior innominate rotation | ASIS high, functional leg appears short |
| Pronated foot | Navicular drop, Achilles valgus |
| Supinated foot | High arch, lateral weight bearing |
Functional vs Anatomical Leg Length
Anatomical leg-length discrepancy is a true bony difference measured on imaging or standing radiographs. Functional discrepancy results from pelvic obliquity, sacral base unleveling, or soft-tissue asymmetry and changes with positioning.
- Seated-heel comparison helps distinguish functional from anatomical short leg.
- Standing-heel comparison reflects the combined effect of anatomy and function.
- Treat the pelvis/SI before assuming an anatomical short leg.
Q: A patient supinates the foot during gait. Which talar motion is likely restricted?
A: Eversion / dorsiflexion mechanics at the subtalar/talocrural complex are often restricted in a supinated foot.
Q: How do you distinguish functional from anatomical short leg on exam?
A: Compare standing and seated heel heights. A difference that persists in sitting is more likely anatomical; one that resolves suggests pelvic/SI or soft-tissue dysfunction.