What stimulates tendon healing?

The right stimulus at the wrong stage is a brake: why the list needs a rule before it is used

What stimulates tendon healing is answered everywhere with a list, mechanical load first, then protein, vitamin C, sleep and the rest, and the lists are not wrong, but a reader who takes a list to an injured tendon without a rule for when each item applies will get hurt by the first item on it, because the stimulus a tendon responds to most strongly is also the one most often applied at the wrong time. The rule the honest page adds is that the right stimulus at the wrong stage is a brake. Mechanical load is the stimulus. A tendon's cells, the tenocytes, sit in rows between the collagen fibres and sense the strain of the fibres around them through their membranes and the connections between cells, and they answer strain with collagen synthesis, with the enzymes that remodel the matrix, and over time with the alignment of new fibres along the direction of pull; a tendon that is loaded within its capacity synthesises more collagen for about three days after each session and, over months, grows stiffer and in young people larger, while a tendon that is unloaded drops its synthesis below baseline and loses matrix quality within weeks. That is the biology behind every tendinopathy programme and every rehabilitation protocol, and it is true. But a tendon that has just torn or been repaired is not a tendon with a capacity to load within. In the inflammatory stage, the first days, the repair is held together by clot and by the sutures a surgeon may have placed, and has almost no tensile strength of its own, so a heavy load through it does not stimulate the tenocytes, which have not yet arrived in number; it gaps the repair, pulls the stitches through the tissue or tears the clot, and the healing restarts from a worse position. The mallet finger is the plainest example: the extensor tendon avulsed from the fingertip heals only if the end joint is held straight continuously for six to eight weeks, and a single bend in the early weeks lets the ends separate and the healing fail, so for that tendon the stimulus that heals every other tendon is the thing that prevents healing. The opposite error is as common and less noticed. Rest continued into the remodelling stage, when the proliferative scaffold has formed and the tendon needs load to turn its disorganised type 3 collagen into aligned type 1, leaves the repair bulky, weak and poorly aligned, with synthesis below baseline and a stiff joint beside it, which is how a cautious reader who waits for the tendon to feel ready before loading it arrives at a tendon that never does. The flexor tendon surgeons found this in the hand decades ago, when six weeks of immobilisation after repair gave stiff, adhered fingers and early controlled motion gave mobile ones, and the Achilles rupture trials found it again when early weight-bearing in a boot matched cast immobilisation for re-rupture and beat it for function. So the list is read as a stage-matched list or not at all.

The stage-matched list, the supporting cast that runs underneath every stage, and where collagen and the clinic's options attach

The stage-matched list has three entries for load and one supporting cast. While inflammatory, in the first days, the stimulus is protection and gentle motion: a splint, boot or sling that holds the repair at a length where its ends stay together, with gentle movement of the joints around it within the protected range, which keeps the repair from sticking to its sheath and keeps synthesis in the uninjured tendon from falling, without loading the repair itself; for a mallet finger even the gentle motion is withheld from the end joint. Through proliferation, over the following weeks, the stimulus is progressive controlled motion and weight-bearing: more range, then partial weight through a boot, then full weight, then light resistance, each step gated by the tissue's response, with new pain, swelling or a sense of giving way the signals that a step was too large and should be retaken smaller, and nothing gated by the calendar, since the proliferative scaffold strengthens at a rate that varies with the tendon, the injury and the person. Through remodelling, from the second or third month onward for a rupture and from the first session for a tendinopathy whose remodelling has stalled, the stimulus is heavy slow progressive loading: isometric holds for pain, then heavy slow resistance at loads near the heaviest manageable, every second or third day to match the seventy-two hour synthesis curve, then energy storage loading, hops and running, as the tendon tolerates, with return to sport decided by tests of strength and function rather than by the month; the tenocyte's full shopping list is on the stimulates tendon repair page. The supporting cast runs underneath every stage rather than belonging to one. Protein at the intakes an injured person needs, around 1.6 to 2 grams per kilogram, supplies the amino acids that the new matrix is built from. Vitamin C is the cofactor without which the collagen chains cannot be stabilised, and a deficient reader heals poorly in any tissue. Not smoking matters because nicotine constricts the vessels that bring the inflammatory and proliferative cells to a tendon that has few vessels to begin with. Sleep is when growth hormone and the night's repair signalling peak. Blood glucose control for a diabetic reader removes the glycation that stiffens and weakens collagen and the microvascular damage that slows every stage. And a course of fluoroquinolone antibiotics or a corticosteroid injection into a tendon are brakes worth naming, since both weaken tendon collagen. Collagen's protocol attaches to the loading session in the remodelling stage: 15g gelatin with vitamin C about an hour before loading raised a synthesis marker in healthy men, and 2.5g beside six months of calf strengthening improved Achilles tendinopathy more than placebo beside the same exercise, so the adjunct belongs beside the heavy session and nowhere earlier. The clinic's options, corticosteroid or platelet-rich plasma injections, shockwave, and surgery, are not stimuli for a healing tendon; they are options for a remodelling that has stalled despite months of loading, with evidence that is weaker than the loading's and, for corticosteroid, a short-term gain and a worse year. The worked example is the adjunct at habit scale, stated on its true terms: two capsules, 1200mg hydrolysed type 1 marine collagen with 12mg vitamin C at 15% of its reference value plus zinc, 120 for £16.99 at 28p a day, lab tested and UK made, below the 15g protocol dose, carrying vitamin C's collagen formation sentence for cartilage and bones and no tendon claim. What stimulates tendon healing: load, matched to the stage, with the right stimulus at the wrong stage a brake.

What to check on the label