Heel Off Phase of Gait - Wheeless' Textbook of Orthopaedics

- Discussion:
- at heel off the resultant force passes in front of the knee and acts to extend the joint (hyper-extension moment);
- as resultant forces passes in front of metatarsal heads, knee joint flexes & mechanical forces
act in direction of flexion once again;
- knee has extended to approx 178 deg;
- is probably being initiated by the biarticular gastrocnemius which is also helping to prevent
hyperextension of the knee from occuring;
- peak electrical activity of gastrocnemius occurs shortly after heel off;
- since mechanical forces are acting to extend knee at this time, and since hamstrings are inactive,
it is reasonable to assume that gastrocnemius is helping to prevent knee hyperextension;