Functional biomechanics of the lower limb Ben and Matt. 24th July 2011 Principles of function Gravity Ground reaction Eco-concentric eccentric loading (preload) of a muscle (or group) is essential for its subsequent concentric action. Eccentric deceleration. Proprioception Mass and momentum Subconscious muscle reaction Real and relative motion The functional approach considers all planes of motion - sagittal, transverse, and frontal. If there is an area where movement is reduced, first work with the positive movement; the movement the patient can do. This improves the negative movement through recoil from a position of ease into the restriction. Phases of gait Contact phase Midstance phase Propulsive phase Swing phase Gait In heel strike (in dorsiflexion) the calcaneus contacts the floor in inversion. The knee is almost in full extension. As the movement progresses into plantar flexion, decelerated by tibialis anterior, the calcaneus moves into eversion. This causes relative dorsiflexion at the talocrural joint. This preloads soleus, which decelerates dorsiflexion, and is important in function as an extensor of the knee. The medial arch flattens during pronation and helps absorb ground forces. Pronation works to absorb shock primarily through 2 mechanisms. 1) The foot retractions through the talus adducting and plantar flexing. 2) Eversion allows tibial internal rotation which unlocks the knee into flexion. The internal rotation of the tibia causes internal rotation of the femur, then flexion of the hip and anterior rotation of the inominate. Internal rotation of the femur preloads the external rotators. At this point / phase (front leg), the movements occur faster closer to the floor (ʻbottom upʼ) tibial internal rotation occurs faster than femoral rotation causing relative internal rotation of the knee. Femoral internal rotation occurs faster than inominate rotation (in the transverse plane), causing relative internal rotation of the inominate. As the medial arch flattens, the cuboid and the navicular line up and pivot on each other. This is a position of flexibility, force absorption and preload. Preload is simply eccentric
muscle action which allows for suitable concentric muscle response. The midfoot moves back into some supination and the calcaneum into some inversion, creating greater stability. This is initiated by the swing phase of the other leg. When the foot is supinated the sacrum is nutated, allowing for force transference. When the foot is pronated, the sacrum is counternutated and ʻlocked upʼ. Analogy of catching a baseball and allowing the arm to ʻbuckleʼ. The other leg now swings around creating external rotation of the stance leg. In this phase, the movements occur faster higher up (ʻtop downʼ) rotation of the inominate occurs faster than femoral external rotation, causing relative internal rotation of the femur, and similarly further down causes relative rotation of the tibia on the femur. In the swing phase the hip drops on the stance leg (lateral tilt). This causes abduction at this hip, and preloads psoas in all 3 planes (sagittal - extension, transverse - rotation/ swing, frontal - lateral tilt). Flexor hallucis longus and the plantar fascia are preloaded by dorsiflexion of the first toe in the propulsive phase (the Windlass mechanism). Fibularis longus, tibialis anterior and tibialis posterior reform the arch creating stability for the ʻexplodeʼ of the propulsive phase. Fibularis longus plantar flexes the first ray to enable toe off. It also act to maintain the locked position of the mid tarsal joint via it's tendon running under the cuboid. Consider which bone is moving faster, which muscles are decelerating, and which muscles are being loaded. In the LEx, the relative movement is named by the movement of the distal bone, e.g. tibial internal rotation - where the tibia is moving faster than the femur. In the spine the relative movement is named by the movement of the proximal bone. Pelvic movements Rotation anterior rotation in heel strike (in the sagittal plane), and transverse plane rotation Tilt Lateral shift Stepping matrix Sagittal plane motion - the patient is asked to step forwards and backwards Frontal plane motion the patient is asked to step to each side (abduction and adduction) Transverse plane motion the patient is asked to step around into internal and external rotation Foot analysis Normal walking Walking in inversion Walking in eversion Squat walking (low ceiling)# Long strides
Hip analysis Wide stance walking - may implicate the adductors and psoas (front butt) Narrow stance walking - may implicate the back butt Walking in internal rotation Walking in external rotation Monkey walking Look for health, not dysfunction find the transitional zone (trasma); tweaks should be made as close to this as possible, but remaining within the limits of function. Tweaks Movement Range Speed Stability Weight Environmental e.g. orthotics, using walls as barriers to lunges Foot assessment (prone) Hold the talus with one hand, between forefinger and thumb, and hold the fifth metatarsal with the other hand. Move the foot into abduction and adduction, feeling for movement of the talus and noting whether movement is equal. Then find the neutral point of movement and fix the talocrural joint into dorsiflexion. Observe the calcaneum and the tibia they should be in line. Make sure the fat pad does not influence this assessment. Then observe vertically to assess whether there is any forefoot varus or valgus. Findings could include: Rearfoot varus Rearfoot valgus Forefoot varus - This is the most common seen in practice. Causes excessive compensatory internal rotation at the hip and commonly causes femoral acetabular impingement (FAI). In midstance there is an overpronatory phase. It can also cause sciatic nerve problems and tibialis anterior tendinopathy/ʻshin splintsʼ. Sciatic nerve problems occur due to excessive stretch of the nerve. Shin splints (anterior compartment) can occur due to the increased requirements of the muscles required to decelerate the greater range of pronation. It can also lead to torsion at the knee and can cause meniscal problems. Forefoot valgus - First toe, and others toes ʻslapʼ the floor. Looks like a cavus foot. Tend to get lateral knee/meniscal problems. Also associated with gluteal bursitis and lumbar spine problems. It has a compressive effect.
Remember to assess the medial border of the foot in both supination (locked) and pronation (unlocked). Assessing which hip is problematic Wide based frontal plane lunge. Start with the foot internally rotated on one side (front leg), which creates internal rotation at the hip, then lunge as far as possible onto this leg. Return to neutral. Move the same foot into an externally rotated position and lunge again. If the movement range is the same, it is likely there is an adductor problem on the other leg. If the movement is now greater this indicates a problem with the same side hip. Repeat on the other side. Example Patient does not go through calcaneal eversion on the right during gait, and passively. Implications reduced tibial internal rotation and consequently the chain reaction above reduced femoral internal rotation causes lack of eccentric preloading of the external hip rotators, which weakens them. This patientʼs gluteus maximus on this side appeared to ʻjump outʼ more than / sooner than the other side. Possible exercise stand in split-stance, weight onto right foot, supported by hands onto wall in front if necessary, step the other leg into and out of external rotation. This encourages eversion and strengthens the external rotators on the other side (adds preload / internal rotation too). Some further points Marathon runners Usually have an immobile thoracic kyphosis. Exercise - running upstairs is usually helpful. The adductors decelerate both flexion and extension at the hip. Loaded in split stance. Dynamic foraminal gapping can be a useful technique. As usual, but use the patientʼs UEx as a driver for side-bending and rotation by reinforcing active UEx movement. Type 1 coupling: Side-bending and contralateral rotation: OA, TSp. Type 2 coupling (2 - together): Side-bending and ipsilateral rotation: CSp, LSp. Facet irritation antalgic posture gaps the joint in every plane - flexion (AP), rotation towards (transverse), side-bending away (frontal). Same and same rehab etc for facet?
Hannah, Gayle, SJ, and Kathryn. Checked by Matt and amendments made, August 2011. From: Hannah Brunt <hannahbrunt@yahoo.co.uk> Subject: email to Ben and Matt - hope this is ok...? sorry, a bit hectic here x Date: 12 August 2011 20:38:48 GMT+01:00 To: SarahJane <Sjintheuk@yahoo.com.au> 1 Attachment, 29.5 KB Hi Ben and Matt, Me, SarahJane and Gayle have got together and have come up with some notes summarising our understanding of what you covered during the course. It would be great, if you still don't mind, if you could have a look and fill in the gaps for us; i'm sure there'll be many! Thanks again for a great course. Kind regards, Hannah Biomechanic doc (29.5 KB)