CONDITION
Medial Shoulder Instability
Medial shoulder instability refers to a condition in which the structures that normally hold the shoulder joint in position on its inner side become lax or damaged, allowing abnormal movement or partial displacement of the joint during activity. This can occur after injury to ligaments, tendons, or the joint capsule, or it may develop gradually in some dogs without a clear inciting event. Owners often notice lameness that may be subtle at first, sometimes appearing after exercise or play and improving with rest. The leg may appear to be carried differently, or the dog may show reluctance to bear weight fully on the affected limb. In some cases, the shoulder may feel unstable or appear to shift when the limb is moved in certain directions. This page explores the observable signs that may suggest shoulder instability, the anatomical changes that underlie the condition, the investigations used to assess the joint, and the range of approaches—both conservative and surgical—that exist for managing it. The information is intended to help you understand what may be happening and what questions might be useful to consider.
Why this matters now
Medial shoulder instability tends to appear in young to middle-aged dogs, often between one and five years of age, though it can develop at any stage of life. Certain breeds with naturally looser joint conformation or those engaged in activities involving rapid direction changes—such as agility work or ball chasing—may be more susceptible. In some cases, the condition follows a single traumatic event, whilst in others it develops gradually without a clear moment of injury, possibly reflecting cumulative strain on supporting structures over time.
The course of medial shoulder instability varies considerably between individuals. Some dogs experience mild, intermittent lameness that remains relatively stable for months or years, whilst others show gradual worsening as the joint capsule and surrounding ligaments stretch further or as secondary changes develop within the cartilage and bone. In a subset of cases, the instability may stabilise spontaneously if compensatory muscle strength develops or activity levels are naturally reduced, though persistent abnormal movement often leads to progressive discomfort and functional limitation.
Signals & patterns
Early signals
Intermittent front-limb lameness
The dog may carry one front leg slightly differently after periods of exercise, particularly if play has involved sudden turns or jumping. The lameness often improves after rest, which can make it easy to overlook in the early stages.
Reluctance to extend the leg fully
When walking or stretching, the affected limb may not reach as far forward as the opposite side. This subtle shortening of stride can reflect discomfort when the joint is placed under load in certain positions.
Shifting weight when standing
An owner may notice the dog redistributing weight between the front legs whilst standing still, or resting the affected limb with the paw slightly lifted or rotated. This behaviour often indicates that full weight-bearing is uncomfortable.
Reluctance to climb stairs or jump
Activities that require the shoulder to bear concentrated force during push-off may be avoided or performed hesitantly. The dog may pause before ascending stairs or decline to jump onto furniture that was previously accessible.
Later signals
Persistent lameness at rest
As the condition progresses, lameness may become noticeable even during slow walking or after minimal activity. The shoulder may appear stiff when the dog first rises from lying down.
Visible muscle loss over the shoulder
Chronic reduced use of the limb can lead to atrophy of the muscles around the shoulder blade and upper arm, which may become apparent when comparing the two sides. This reflects prolonged offloading of the affected leg.
Palpable instability or clicking
In some cases, gentle manipulation of the shoulder may reveal abnormal movement or a sensation of the joint shifting. Occasionally, a clicking or clunking sound can be felt or heard as the joint moves through certain ranges.
Click to read about the biological mechanisms
How this is usually investigated
Options & trade-offs
Last reviewed: Invalid Date ·