How Does a Broken Bone Heal? Nature’s Four-Step Fix!

Physio rehab after fracture in Phnom Penh

Bone healing is a biological masterpiece

Bone is one of the few tissues in the human body capable of regenerating itself completely. Unlike muscles, tendons or ligaments, which form scar tissue, bone rebuilds a structure almost identical to the original.

The process is complex yet beautifully orchestrated. It follows predictable phases — but their duration, quality, and success depend heavily on load management, circulation, and appropriate rehabilitation.

Physiotherapy does not “accelerate” bone healing, but it optimises the environment so the bone can heal efficiently.

Phase 1: Inflammation — the body’s emergency response

Immediately after a fracture, the body enters an inflammatory phase lasting a few days. Blood vessels rupture, bleeding occurs around the fracture, and a hematoma forms.

This inflammation is not a problem — it’s a biological necessity. It triggers cellular activity that initiates the healing sequence. Pain, heat, and swelling are normal signs that the body is responding exactly as it should.

Phase 2: Soft callus — the bridge that stabilises the bone

During the following weeks, the body creates a soft callus. This temporary tissue stabilises the fracture, acting like a biological splint. It is flexible, not yet strong, and cannot tolerate heavy loading.

This phase is critical: too much movement or premature weight-bearing may disrupt callus formation. Too little movement leads to joint stiffness, loss of muscle strength, and longer rehabilitation times.

The art of physiotherapy in this stage lies in finding the right balance between protection and controlled mobility.

Phase 3: Hard callus — the transition to real bone

Over the next several weeks, the soft callus is gradually replaced by a hard, mineralised structure. This is when clinical healing becomes visible on X-rays.

The bone is now stable enough to tolerate progressive loading. For patients, this is the turning point: exercises become more functional, muscles regain strength, and pain gradually decreases.

However, despite visible improvement, the bone is not yet at full strength — meaning that return to intense sport too soon may lead to setbacks or re-injury.

Phase 4: Remodeling — the long game of optimisation

Remodeling can last months to years. The bone reshapes itself according to mechanical forces applied through daily activity, walking, and progressive strengthening.

This phase determines the final quality of recovery. If the load placed on the bone is too low during this period, the structure remains weaker and less adapted. If load increases progressively, the bone becomes stronger and more resilient.

This is where physiotherapy plays its most important role: guiding progression based on symptoms, mobility, strength, and long-term functional demands.

What physiotherapy actually changes in bone healing

Physiotherapy does not speed up the biological timeline — no treatment can. But it ensures that the bone heals under optimal mechanical conditions. Proper guidance prevents stiffness, muscle loss, fear-avoidance, and poor movement patterns that often follow immobilisation.

Rehabilitation focuses on restoring confidence in movement, rebuilding surrounding muscles, and preparing the patient to return to sport or activity safely.

Bone healing is a biological process. Recovery is a behavioural one. Physiotherapy supports both.

The key message

Bone healing follows a natural, scientifically predictable sequence. But the quality of your recovery depends on what you do during those weeks: too much protection leads to weakness; too much intensity leads to irritation.

Progressive loading, guided rehabilitation, and realistic expectations are what transform a biological healing process into a full functional recovery.

References:

1. Sheen JR, Mabrouk A, Garla VV. Fracture Healing Overview. [Updated 2023 Apr 8]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2025 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK551678/