# A Rare Case of Spontaneous Healing of an Anterior Cruciate Ligament Tear

## TL;DR

A 33-year-old woman with a complete ACL tear experienced spontaneous healing after choosing non-operative treatment, as shown by an MRI 11 months later.

## Contribution

This case report documents a rare instance of spontaneous healing of a complete ACL tear in a sedentary adult.

## Key findings

- The patient's MRI 11 months post-injury showed a completely intact ACL, indicating spontaneous healing.
- Non-operative treatment, including a knee brace and physical therapy, was associated with improved range of motion and pain.
- The case suggests that spontaneous ACL healing may be possible, particularly in certain tear types.

## Abstract

Anterior cruciate ligament (ACL) injuries are among the most common knee injuries in the United States. The ACL is an intra-articular ligament that resists anterior tibial translation and provides rotational stability. Most ACL injuries occur through non-contact mechanisms and are typically diagnosed based on history, physical examination, and confirmatory MRI. Treatment options include operative and non-operative management, with the latter focusing on restoring functional stability rather than expecting the ACL to heal spontaneously.

In this case report, we present a 33-year-old female patient with a sedentary lifestyle who experienced a popping sensation and immediate swelling after twisting her knee while sitting down. She presented to the clinic one week later, reporting knee instability and a dull, aching pain rated 7/10. Physical examination revealed pain with passive knee extension and positive patellar compression, Clarke’s inhibition, McMurray’s, and Lachman’s tests. MRI confirmed a complete ACL tear and a full-thickness cartilage defect in the medial facet of the patella. The patient opted for non-operative treatment, including a crossover knee brace and physical therapy. Over multiple follow-up visits, her range of motion and pain improved. Eleven months post-injury, a follow-up MRI ordered to evaluate a suspected reinjury unexpectedly revealed a completely intact ACL, indicating spontaneous healing.

This case highlights a rare instance of spontaneous ACL healing in a sedentary adult who chose conservative management. Although non-operative therapy typically aims to restore function rather than facilitate ligament healing, emerging evidence suggests spontaneous ACL healing is possible, particularly in proximal femoral single-bundle tears. Further research is needed to establish standardized conservative treatment protocols that optimize outcomes and promote ACL regeneration.