RSSTERMINAL KNEE EXTENSION
August 7, 2009 by David Fitzgerald
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Filed under Physiotherapy Blog
Impairment of terminal knee extension is a frequent clinical scenario which is fairly routine for most physiotherapists. A recent clinical experience got me thinking more deeply on this topic. Firstly we are not talking about quadriceps inhibition i.e. patients who have a full passive range but an inability to actively control. This type of case doesn’t usually pose a major clinical challenge as there are a host of tools in our armoury to facilitate quadriceps activation – of which static inner range quads is probably my least frequently used technique. So we are talking here about patients who describe some form of discomfort or inability to terminally extend the knee. The first clinical priority is to identify the pathology and hence the factors limiting extension:
Factors limiting terminal knee extension
- Intra-articular derangement.
- Anterior impingement.
- Posterior restriction.
Internal derangement – namely meniscal pathology is a fairly obvious cause of extension block. Usually this is identifiable as a loss of extension of at least 10° and often associated with a “springy” painful end-feel. It is always worth trying passive relocation techniques in these cases to see if cartilage fragments can be relocated and terminal knee extension re-established. This of course is no guarantee that it will be maintained but can be used as a clinical guideline for onward referral should the pattern become recurrent.
What sparked my attention was a less clear cut case of impaired terminal knee extension where symptoms were reported at terminal stance, full weight bearing knee extension, hamstring stretch and calf stretch. These symptoms fluctuated from anterior intra articular pain, posterior capsular strain to vague non-specific intra articular discomfort. MRI scans were normal and intra articular pathology excluded.
Quantifying the extent of extension impairment
The first issue of interest was quantifying the extent of extension impairment.
Visual observation in standing showed slight side-to-side asymmetry but not sufficient to make useful clinical judgements.
Long sitting popliteal crease to bed distance was a useful marker where posterior leg surface contact area can easily be visualised and confirmed by attempting to slide the therapists hand underneath the leg.
Extension over pressure in this position is also a useful supplementary adjunctive test. Remember the accessory movement here should be an upward pull through the heel to induce anterior translation of the tibia with the counter pressure above the knee joint line on the anterior femur in order to facilitate the anterior translation of the tibia on (a fixed) femur in terminal extension.
Prone lying with the foot extended over end of the bed is an a good position to allow strong leverage to be placed through the leg but the clinical challenge is preventing hip elevation secondary to the downward pressure through the lower leg. This can be countered with belt fixation or therapist fixation of the posterior thigh but nevertheless can be a significant impediment to effective technique.
Another useful technique is to fix the femur with downward pressure with the patient in long sitting and then seek to initiate active quadriceps contraction. The distance of the heel raise from the underlying bed is another useful and easy measurable indicator of extension range.
What combinations of accessory joint motion would you use to facilitate extension ?
Enjoy the clinical challenge.
David
