How can a physio tell if I have tendonitis rather than a muscle strain? 

A physiotherapist distinguishes between tendonitis and a muscle strain by assessing the exact location of the pain, the timing of the symptoms, and the specific movements that trigger discomfort. While both conditions involve soft tissue injury, they affect different parts of the musculoskeletal system and require distinct rehabilitation approaches. In the United Kingdom, physiotherapists are highly trained to use physical palpation and orthopedic loading tests to identify whether the injury is in the muscle belly or the fibrous tendon that attaches the muscle to the bone. 

What We’ll Discuss in This Article 

• The anatomical differences between muscle tissue and tendon tissue. 

• How the location of tenderness helps identify the injured structure. 

• The role of isometric and eccentric loading in diagnosis. 

• Differences in how pain behaves during and after activity. 

• Why the mechanism of injury (sudden vs. gradual) is a key clue. 

• NHS-aligned management strategies for tendons and muscles. 

Anatomical location and palpation 

One of the most immediate ways a physio identifies the injury is through palpation, which involves feeling the tissues to find the center of the pain. Muscle strains typically cause pain in the “belly” of the muscle, which is the fleshy, thicker part of the tissue. Tendonitis, however, causes localized tenderness at the point where the muscle transitions into a tough, fibrous cord and attaches to the bone. According to NHS information on tendonitis, the pain is usually very pinpointed over a joint, whereas a muscle strain feels more widespread across the limb. 

Assessing the mechanism of injury 

The way the injury started provides significant clues for a physiotherapist. Muscle strains often occur following a sudden, explosive movement, such as sprinting or lifting a heavy object, often resulting in an immediate “pulling” or “tearing” sensation. Tendonitis is usually an overuse injury that develops gradually over weeks or months due to repetitive strain or a sudden increase in exercise volume. While acute tendon tears can happen, the NICE clinical standards for musculoskeletal pain highlight that a slow onset of aching usually points toward a tendon issue rather than a muscle tear. 

Strength and resistance testing 

A physiotherapist will use specific resistance tests to see how the tissues react to being loaded. Muscle strains often cause significant pain during a concentric contraction, which is when the muscle shortens under load. In contrast, tendonitis is often most painful during isometric holds (holding a position under tension) or during the “warm-up” phase of an activity. If the pain is sharpest during a sudden stretch or a forceful contraction in the middle of the muscle, it suggests a strain. If the pain is a deep, localized ache at the joint that increases as the load becomes heavier, it is more likely to be tendonitis. 

The behavior of pain during activity 

The timing of your pain during exercise is a classic diagnostic marker. Tendonitis often follows a “warm-up” pattern, where the pain is stiff and sore at the beginning of an activity, improves as you continue moving, but then becomes significantly worse after you stop and cool down. Muscle strains do not usually “warm up” in this way; instead, the pain tends to be more consistent throughout the activity and can feel like a sharp jab if the muscle is stretched. A physio will ask about your morning stiffness, as tendons are notoriously stiff after rest, whereas muscle strains may feel more like a constant soreness. 

Differences in swelling and bruising 

Visual signs can also help distinguish the two conditions. A significant muscle strain often involves the rupture of small blood vessels within the muscle fibers, leading to visible bruising (ecchymosis) and broader swelling around the limb. Tendonitis rarely causes bruising unless there is a complete rupture. Instead, tendonitis may involve a very localized thickening of the tendon that feels like a hard lump, or in the case of associated bursitis, a squishy, fluid-filled swelling right next to the joint. 

Rehabilitation and recovery paths 

Identifying the correct structure is essential because the treatment for a muscle strain is quite different from that for tendonitis. Muscle strains require a period of rest followed by gentle stretching to prevent scar tissue from becoming too tight. Tendonitis, however, often requires “load management,” where the tendon is gradually subjected to heavier weights, specifically through eccentric exercises, to stimulate the remodeling of collagen fibers. In the UK, a physiotherapist will create a tailored plan that ensures the tissue is challenged enough to heal without being overloaded back into a state of inflammation. 

Conclusion 

A physiotherapist can tell the difference between tendonitis and a muscle strain by looking at the location of your pain, the way the injury started, and how the joint reacts to specific types of weight-bearing. Muscle strains are often sudden and felt in the fleshy part of the limb, while tendonitis is usually a gradual, localized ache at the joint. Correct diagnosis ensures that you follow the most effective rehabilitation path for a full recovery. If you experience severe, sudden, or worsening symptoms, call 999 immediately. 

Authority Snapshot 

This article examines the clinical methods used by physiotherapists to identify and distinguish between different soft tissue injuries. It has been written by the MyPatientAdvice Medical Writing/Research Team and reviewed by Dr. Rebecca Fernandez to ensure clinical accuracy and safety. The information provided is strictly aligned with the current NHS and NICE protocols for the management of musculoskeletal injuries in the United Kingdom.