Musculoskeletal Dysfunction

When we are presented with a patient who is lame, but radiographs are negative, what tests do we have to determine the source of lameness? This is an area where understanding physical therapy diagnostic techniques can be of great benefit to veterinarians. In order to diagnose a problem, we must be very familiar with what is normal in joint, ligament, muscle and tendon behaviour. A physical therapist approaches a patient in a way that focuses upon the soft tissues surrounding the bones and joints and upon the interaction of joint surfaces during movement.

Range of Motion

Range of motion (ROM) is determined by osteokinematics and arthrokinematics. Osteokinematics (osteo = bone; kinematics = motion) is the gross motion which occurs when bony segments move around a joint axis. Elbow flexion is an example of osteokinematics. This range of motion is measured in degrees, using a goniometer. There are two kinds of osteokinematics, active range of motion (AROM) and passive range of motion (PROM). The difference between these two can be an important diagnostic tool. AROM is defined as motion performed by the patient, while PROM is motion performed by the therapist. It is PROM that we measure in our canine patients using a goniometer.

The goniometer is composed of two parts with a central hinge. When measuring ROM, the stable arm of the goniometer is placed on the proximal segment; the hinge, or fulcrum, is placed over the joint axis, and the moving arm is placed over the distal segment. Using elbow flexion as an example, the stable arm of the goniometer would be placed on the humerus, using the greater tubercle as the proximal landmark, with the fulcrum at the lateral epicondyle. The moving arm would be placed along the ulna, using the lateral styloid process as the distal landmark.

If, in our example of elbow flexion, our patient is reluctant to flex the elbow in normal activity ('decreased AROM in elbow flexion'), but we can get normal, non-painful range of motion on flexing the elbow for him ('normal PROM'), what might our differential diagnosis be? It is this type of problem-solving which the physical therapist applies to the patient.

Flexibility

The first issue that we must address in this example is the difference between ROM and flexibility. ROM refers to joint motion while flexibility refers to muscle length, so there is no such thing as 'joint flexibility'. Problems associated with decreased flexibility are most often noticed in muscles that cross two joints. In our elbow flexion example, if we have triceps muscle (long head) shortening, and we test the elbow range of motion with the shoulder in flexion, where the triceps is on slack, the elbow will have a normal ROM. If we then place the shoulder into extension, and our range of motion is now limited, all arrows point to triceps flexibility as our probable source of problems.

End Feels

What else can limit ROM? Possibilities include intra-articular lesions, joint capsule tightening, ligament shortening, pain and swelling in or near the joint. How can we tell these apart? Physical therapists use 'end feels' here. An end feel is defined as the sensation or feeling which the therapist detects when the joint is at the end of its available PROM. There are several end feels that are used. We will discuss the five most common.

 Bony end feel is a hard (abrupt) sensation that is blocked by bone, and is painless in the normal patient. An example of normal bony end feel is elbow extension. Try this on yourself. If you have a normal elbow, the sensation you feel at the end of extension is one of bone-on-bone restricting the elbow from extending further. In a pathological joint with a bony end feel, the sensation will happen before the expected end range of motion. The common veterinary example is hip abduction in the hip dysplastic patient.

 Soft tissue approximation is a soft, yielding end feel, where the block is soft tissue (muscle or fat). In the normal example, stifle flexion is limited by the gastrocnemius engaging the hamstring group. In a pathological joint, this end feel would be found when hip flexion is limited by adipose tissue in the patient with a large flank lipoma.

 A firm end feel gives the sensation of a firm, elastic response with a slight give. Carpal flexion in the normal patient will have a firm end feel. Try this on yourself. In the abnormal joint, a firm end feel will happen before the normal end ROM, such as hip extension in the hip dysplastic patient.

 The springy end feel is always abnormal. There is a spring, or rebound, before the normal end range of motion, and it may be painful. The most common example of springy end feel is the meniscus in stifle extension when the canine patient has a medial meniscal tear.

 An empty end feel is also always abnormal. In this circumstance, there is no mechanical resistance to PROM, but pain causes the patient to resist any further motion. An empty end feel indicates serious pathology, such as a neoplasm.

To summarise, when the physical therapist evaluates the patient, they are assessing ROM (both active and passive), flexibility and end feels. The next step involves assessing arthrokinematics, accessory joint motions, ligamentous stability and muscle strength.

Arthrokinematics

The movement that occurs between two joint surfaces during AROM is called arthrokinematics. This is a passive, involuntary movement. It can be broken down into roll and glide. Roll is the action of one joint surface on the other in a motion equivalent to a tyre rolling along the pavement. Glide is the action equivalent to a tyre skidding along the pavement. Each motion is essential to normal joint motion. Both motions are required to have normal osteokinematic range of motion.

Accessory joint motion, which describes arthrokinematic motion, can be affected by abnormal tightening of the joint capsule or the joint ligaments. How can we resolve these abnormalities? The answer lies in joint mobilisations.

Joint Mobilisations

A joint mobilisation is a manual technique used to assess a joint and to stretch the joint capsule or ligaments. Joint mobilisation is accomplished through glides, oscillations, distractive forces and/or compressive forces on the joint surfaces. There are several grading systems to rate the joint mobilisations. The Kaltenborn Grading System is commonly used in the US. When assessing a patient's joint, the scores can read 0 to 6, with 0 being a fused joint, 6 being a luxated joint and 3 being normal.

When treating a patient, the glides are ranked grade I to V. A grade 1 glide is a fast, small-amplitude glide at the beginning of available range. Grade II glides are slow, large-amplitude glides through the first half of range of motion. Grade III glides are slow, large-amplitude glides in the mid to end range of motion. Grade IV glides are fast, small-amplitude glides at end range of motion. A Grade V mobilisation is called a manipulation and is a small-amplitude quick thrust performed at the end of the arthrokinematic range. To perform a manipulation, one must be trained in veterinary chiropractic.

The goals of joint mobilisation are to stretch the joint capsule and ligaments, to create enough space for proper joint arthrokinematics, which allows for normal osteokinematics, and to prevent compensation which is the result of decreased ROM.

All of the terms described in this presentation are used every day in physical therapy practice, and are important for anyone wishing to pursue veterinary rehabilitation. There is much more to the practice of rehabilitation than performing new 'therapies'. A valid diagnosis, based upon physical therapy evaluative techniques, is vital for a successful outcome.

References

1.  Bronfort G, Haas M, et al. Efficacy of spinal manipulation and mobilization for low back pain and neck pain: a systematic review and best evidence synthesis. The Spine Journal 2004;4:335–356.

2.  Childs J, Fritz J, et al. A clinical prediction rule to identify patients with low back pain most likely to benefit from spinal manipulation: A validation study. Annals of Internal Medicine 2004;141:920–928.

3.  MacKay C, Davis A, et al. Expanding roles in orthopaedic care: a comparison of physiotherapist and orthopaedic surgeon recommendations for triage. Journal of Evaluative Clinical Practice 2009;15:178–183.