Table 1.
Origin, insertion and action of the major muscles of the proximal pelvic limb
| Muscle | Abbreviation | Origin | Insertion | Action |
|---|---|---|---|---|
| Psoas minor | PMN | Ventral bodies of last 3 thoracic and first 3–4 lumbar vertebrae, crura of diaphragm | Psoas minor tubercle of femur | Flexion of hip |
| Psoas major | PMJ | Vertebral aspect of last 2 ribs, bodies and transverse processes of all lumbar vertebrae | With iliacus onto lesser trochanter of femur | Flexion of hip |
| Iliacus | IL | Pelvic surface of ilium, sacrum and tendon of psoas minor | Lesser trochanter of femur | Flexion of hip |
| Gluteus superficialis | GSP | Gluteal fascia | Third trochanter of femur and ischiadic tuber | Flexion and abduction of hip |
| Gluteus medius | GMD | Gluteal fascia, sacrum and sacro-iliac ligament | Greater trochanter of femur | Extension and abduction of hip |
| Gluteus profundus | GPF | Ischiatic spine | Greater trochanter of femur | Extension and abduction of hip |
| Tensor fascia lata | TFL | Tuber coxae | Via fascia lata onto patella and tibia | Flexion of hip, extension of stifle |
| Biceps femoris | ||||
| Vertebral head | BFV | Spinous and transverse processes of last three sacral vertebrae, caudal fascia, broad pelvic ligament, ischiadic tuber | Blend with femoral and crural fascia and insert onto patella ligament, patella, tibial crest and lastly onto calcaneal tuber via calcaneal tendon | Extension and abduction of hip during stance, flexion of stifle and extension of hock during swing |
| Middle head | BFM | Ischiatic tuber and ischium | As above | As above |
| Caudal head | BFC | As above | As above | As above |
| Semitendinosus | ||||
| Vertebral head | STV | Last spinous and transverse processes of sacrum, caudal fascial, first 3–4 caudal vertebrae and broad pelvic ligament | Medial tibial crest with aponeuroses of gracilis and sartorius and calcaneal tuber via calcaneal tendon which unites with that of biceps femoris to become accessory tendon | Extension of hip during stance, flexion of stifle and extension of hock during swing |
| Pelvic head | STP | Ischiadic tuber | As above | As above |
| Semimembranosus | ||||
| Vertebral head | SMV | First caudal vertebra and broad pelvic ligament | Medial condyle of femur, medial collateral ligament and medial aspect of tibia | Extension of hip during stance, adduction of hip and flexion of stifle during swing |
| Pelvic head | SMP | Ischiadic tuber | As above | As above |
| Sartorius | SRT | Iliac fascia and aponeurosis of PMJ | Via crural fascia onto medial aspect of tibia and onto medial straight patella ligament | Flexion and adduction of hip, flexion of stifle during swing |
| Gracilis | GRC | Pelvic symphysis, tendon of insertion of rectus abdomius and accessory ligament | Via crural fascia onto tibial crest and onto medial straight patella ligament | Adduction of hip, flexion of stifle during swing |
| Pectineus | PCT | Pubis, terminal tendon of rectus abdomius and accessory ligament | Medial shaft of femur (linea aspera) | Adduction of hip |
| Adductor | ||||
| Magnus | ADM | Pelvic symphysis | Medial shaft of femur (linea aspera) | Adduction and extension of hip |
| Brevis | ADB | As above | As above | As above |
| Quadriceps femoris | ||||
| Rectus femoris | RF | Body of ilium | Middle patella ligament to tibial tuberosity and tibial crest | Flexion of hip, extension of stifle |
| Vastus medialis | VM | Craniomedial femoral shaft | As above | Extension of stifle |
| Vastus intermedius | VI | Cranial femoral shaft | As above | As above |
| Vastus lateralis | VL | Craniolateral femoral shaft | As above | As above |
Primary action at each joint is listed first, followed by secondary/auxillary actions (Nickel et al. 1986). Piriformis is part of GMD in the horse and so is not listed as a separate muscle. The hamstring muscles flex the stifle joint during swing but constrain extension during the first half of stance due to the antagonistic action of rectus femoris and the cranial position of the vertical ground reaction force vector (Clayton et al. 2001).