Joint Instability - The Reflexes That Strength Exercises May Miss Following An Injury
When a Joint Gives Way And Damage Happens
Introduction:
A joint may remain unreliable after injury or surgery even when strength returns. Balance and proprioceptive training help restore automatic stability and confidence.
Several times during my life, I have suffered catastrophic damage to my ankles and knees. These injuries required orthopaedic surgery followed by long periods of recovery and rehabilitation. Given the extent of the damage, disabling post-traumatic osteoarthritis, sometimes called arthrosis, was a very real prospect.
Fortunately, that has not been my long-term outcome. Now in my mid-70s, I continue to enjoy unrestricted physical activity. I do not put this down to luck alone. Good surgery helped, but so did patient, persistent rehabilitation that continued decades after the wounds had healed and ordinary muscular strength had returned.
One lesson has stayed with me: a joint is not fully rehabilitated merely because it is strong or no longer painful. It must also recover its ability to sense movement and respond automatically. This becomes especially apparent when an ankle suddenly rolls or a knee gives way without any obvious warning.
Most of us walk without watching every footstep. We cross grass, gravel, broken pavement and uneven ground while looking ahead, talking to somebody or carrying something. The foot meets the ground, detects what is underneath it and adjusts almost instantly. The ankle, knee, hip and trunk cooperate before we have consciously thought about any of it. After an injury, that automatic system may no longer work properly.
A person may say that the ankle suddenly rolls or the knee gives way “for no reason”. They may feel safe on a smooth floor but become anxious on grass or gravel. They may find themselves staring at the ground, carefully choosing where to place each foot. Sometimes the joint has recovered much of its movement and muscular strength, yet it still cannot be trusted.
This is often described as functional instability. There may still be some mechanical looseness, pain or weakness, but the missing part may also be the quality and speed of the joint’s sensory and reflex control.
A joint is more than hinges, ropes and muscles
Ligaments are often described as passive straps joining one bone to another, while tendons attach muscles to bones. That description is mechanically correct, but incomplete. These tissues are also richly involved in sensation and movement control. Sensory receptors in muscles, tendons, joint capsules, ligaments and skin continually report information about:
joint position;
the direction and speed of movement;
muscle length and the rate at which it is changing;
tension through the muscle–tendon unit;
pressure beneath the foot; and
movement towards the vulnerable limits of a joint.
Muscle spindles detect muscle length and rapid changes in length. Golgi tendon organs, situated mainly near the muscle–tendon junction, detect tension through the muscle–tendon unit. Ligaments and joint capsules contain several kinds of mechanoreceptors, including Ruffini, Pacinian and Golgi-like endings.
The messages from these receptors travel through sensory nerves to the spinal cord and brain. The nervous system combines them with information from vision and the balance organs of the inner ear. It then continually adjusts muscle activity throughout the limb and trunk.
If the foot begins to roll on a stone, for example, the protective response cannot wait for a conscious decision. Selected muscles must contract, others must ease, and some must stiffen the joint together. Timing is critical. A strong muscle that reacts too late may be of little help.
How an apparently minor injury can disturb the system
A sprain does more than stretch a piece of connective tissue. It may damage some of the small sensory endings within the injured ligament or capsule. Pain and swelling can also change sensory input and inhibit normal muscle activation. The person then unloads the limb, moves differently and begins to rely on protective habits.
Even a relatively minor injury can therefore disturb the conversation between the joint and the nervous system. With a major ligament rupture, recurrent sprains or reconstructive surgery, the disturbance may be greater.
Surgery may be entirely necessary to restore the mechanical integrity of a badly damaged joint. However, it is also a controlled injury involving incisions, tissue handling, fixation, swelling and a period of protected movement. A repaired or reconstructed ligament does not immediately reproduce the sensory behaviour of the original tissue.
The brain also adapts to what has happened. After weeks or months of pain, instability, bracing or altered walking, it may continue using the protective movement pattern even after healing is well advanced. The rehabilitation task is therefore not only to rebuild tissue and muscle, but to retrain the whole sensorimotor system.
The clue is having to watch every step
One of the clearest practical clues is visual dependence. If a person must look down to place the injured foot safely, vision may be compensating for unreliable information from the ankle, knee or surrounding tissues. The eyes tell the brain where the foot and the ground are because the internal position-sensing system is not yet providing enough confidence.
Balance also depends on the inner ear, the nervous system, strength, pain, reaction time, sensation in the feet, medications and general health. Nevertheless, a new need to watch every step after a limb injury is useful clinical information and should not be dismissed.
Strength is necessary, but it is not the whole answer
Calf raises, squats, step-ups, resistance exercises and progressive loading are all valuable. Strength helps the muscles generate force, protects healing tissues and restores physical capacity.
However, a controlled exercise performed on a firm floor is not the same as responding to an unexpected change beneath the foot. Rehabilitation should also develop balance, joint-position awareness, coordinated co-contraction, reaction speed and confidence under gradually less predictable conditions.
Current ankle-sprain clinical guidelines recommend proprioceptive and balance-focused exercise to reduce recurrent injury. Knee-ligament guidelines similarly recommend neuromuscular re-education alongside strengthening. This is particularly relevant after ankle ligament injury and anterior cruciate ligament injury, but the principle applies much more widely.
The stork stand: a simple comparison
The stork stand is a useful favourite. It is both a rough comparison and, when practised regularly, a simple exercise.
Stand beside a solid bench or heavy chair that will not move. Have another person nearby if there is any concern about falling.
Stand on one leg with the eyes open.
Lift the other foot clear of the floor without pressing it against the standing leg.
Keep the hands free, or stretch the arms sideways like a tightrope walker.
Time how long the position can be maintained before the raised foot touches down, the standing foot hops or the hand grabs support.
Compare sides under the same conditions.
Thirty seconds is sufficient for a simple home comparison. The quality of control is as important as the time. Watch for excessive ankle wobble, the knee collapsing inwards, gripping with the toes, large arm movements or the trunk leaning to rescue the balance.
The two sides need not be identical, and the result is not a diagnosis. Pain, fatigue, previous injuries and natural side dominance can all affect performance. A marked difference, especially when it matches a history of giving way, is worth addressing. The way that this is typically addressed is by practicing balancing exercises, including the stork stand.
Progressing the stork stand
Once ordinary one-leg standing is safe and comfortable, progression may include:
turning the head slowly from side to side;
reaching in different directions with one hand or the free foot;
standing on a folded towel or another mildly compliant surface;
rising carefully onto the ball of the foot and holding there;
catching and returning a light ball; and
responding to gentle, unpredictable movements under professional supervision.
Balancing high on the ball of the foot adds calf and foot strength demands as well as a much smaller base of support. Poor performance at that level does not isolate proprioception, but it is a useful advanced task when the tissues are ready for it.
What happens when the eyes close?
Closing the eyes removes the visual information that may be compensating for poor sensory control elsewhere. A person who is steady with the eyes open may become much less stable when both eyes close.
Closing only one eye is a small progression because vision remains available through the other eye, although depth perception changes. Closing both eyes is the more meaningful challenge. It is also substantially more hazardous.
Do not attempt an eyes-closed one-leg stand unless ordinary balance is already secure. Stand within immediate reach of a fixed support, have someone ready to assist and stop at the first sign of losing control. Frail people, those with dizziness, poor foot sensation or a history of falling should do this only with an appropriately qualified health professional.
A poor eyes-closed result is not specific to a damaged ankle or knee. Vestibular disorders, peripheral neuropathy and neurological conditions can produce the same finding. New or unexplained balance loss deserves proper assessment.
Balance Beam, or Walking the Plank
A short length of timber can provide an inexpensive balance exercise. A piece of 100 × 50 mm timber, traditionally called four-by-two, may be laid securely on the floor and used like a very low balance beam.
Make certain it is straight, sound and unable to slide, tip or rock. Begin with the wider face uppermost and place it beside a wall, with a heavy chair or rail on the other side. Do not use loose furniture that might move when grabbed. Having soft surfaces like carpet, grass, or, better still, gym mats on either side is an added safety measure.
Walk slowly along the timber, looking ahead rather than staring constantly at the feet. At first, touching the wall, chair or other support lightly is sensible. As control improves, reduce hand support, slow the steps, walk backwards, or carry out gentle head turns. The exercise can later become more demanding, such as making a pivot (spin) 180 degrees, but difficulty should be increased only one element at a time.
The aim is not to perform a circus trick, or pretend to be a gymnast. It is to teach the nervous system to receive imperfect information, make rapid corrections and maintain control while attention and vision are directed towards the world ahead.
Progress from predictable to unpredictable
The final stages of rehabilitation should increasingly resemble the demands of ordinary life, work or sport. Depending on the injury, this may include stepping in several directions, walking over uneven surfaces, controlled perturbations, hopping, landing, turning, decelerating and performing tasks while distracted or tired. Controlled perturbations are small disturbances to balance, such as a gentle push, an unstable surface or catching a ball from an unexpected direction. They train the nervous system and muscles to make the rapid, automatic corrections needed when the ground or body moves unexpectedly.
For an ankle, attention should extend beyond the peroneal muscles to the calf, tibialis anterior and posterior, intrinsic foot muscles, knee, hip and trunk. For the knee, hip and trunk control are particularly important. The body does not stabilise a joint in isolation.
Balance work should not be the only component of rehabilitation, just as strength work should not be the only component. Mobility, progressive loading, power, endurance, reaction and task-specific practice must eventually come together.
Do not rush a healing reconstruction
Be the tortoise - not the hare. For my own injuries, I gave them not weeks, not months, but years to complete a full process of recovery.
After surgery or a significant ligament injury, the timing of each exercise is important. An exercise that is useful later may overload healing tissue if introduced too early. Weight-bearing, range of movement, calf loading, hopping and uneven-surface work must follow the surgeon’s and physiotherapist’s restrictions.
Seek reassessment if the joint continues to give way, becomes increasingly swollen or painful, locks, develops new numbness or weakness, or fails to progress. Persistent instability may reflect mechanical laxity, cartilage damage, tendon injury, impaired nerve function or another problem that balance exercises alone cannot correct.
A stable joint is not merely a strong joint. It is a joint that senses, communicates and responds quickly enough to protect itself before conscious thought is required. Following injury or surgery, restoring that automatic ability deserves the same patience and attention as rebuilding muscle.
Further reading
Medical disclaimer: This article provides general educational information and is not a diagnosis or an individual rehabilitation programme. Exercises must be appropriate for the injury, stage of healing, surgical procedure, age and fall risk. Seek advice from the treating surgeon, physiotherapist or other suitably qualified health professional before progressing balance or loading exercises.
Comments