Skeletal Evidence of Knee Injury and Stress

The knee is the largest and one of the strongest joints in the human body. It is a major weight-bearing joint and is subjected to stress and injury even during sedentary daily living. During athletic competition and other strenuous activity, the stress is increased

Bony Landmarks The Body
Fig. 16. These thick, strong tendons and capsular structures that cover the posterior aspect of the knee help mold the contours of the underlying bone (illustration by the author, reproduced with permission from ref. 1; Hughston Sports Medicine Foundation, Inc., Columbus, Georgia).

to incredible levels. Some of these injuries and stresses can produce changes in the bone that become part of the permanent osteological evidence and thus can be used to recreate a pattern of activity. In forensic cases, this type of analysis can lead to a correlation with a medical record and possibly a positive identification. It is important to be able to recognize changes in the bone that are due to injury and to the stresses caused by such factors as misalignment and other mechanical forces.

The process of bone remodeling is controlled by an intricate system of bone deposition and resorption. The biomechanical principles that apply to long-bone response and remodeling are not quite the same as those that apply to synovial weight-bearing joints such as the knee, but the physiological principles are similar.

Knee Kick Reflex Type Stress
Fig. 16. Continued.

At the ends of the femur and tibia, the trabeculae are arranged to resist both tensile and compressive forces. When a change occurs in overall body weight, biomechanical forces, or both, there is a corresponding thickening or thinning of the trabeculae. This change in trabecular thickness, rather than cortical bone remodeling, is the primary stress response at the joint.

Other forces and factors in and around the articular surfaces of weight-bearing joints affect the response to injury and stress. In addition to bone, cartilage is the primary connective tissue involved in and around large synovial joints. Articular cartilage covers the gliding and load-bearing surfaces of the bones; fibrocartilage attaches ligaments and tendons to the bones, and fibroelastic cartilage constitutes the bulk of the interarticular menisci.

Semitendinosus Gracilis

Fig. 17. The tendons of the sartorius, gracilis, and semitendinosus muscles come together as the pes anserinus tendon group. Here the large distal retinacular portion of the vastus medialis is also evident (illustration by the author, reproduced with permission from ref. 1; Hughston Sports Medicine Foundation, Inc., Columbus, Georgia).

Fig. 17. The tendons of the sartorius, gracilis, and semitendinosus muscles come together as the pes anserinus tendon group. Here the large distal retinacular portion of the vastus medialis is also evident (illustration by the author, reproduced with permission from ref. 1; Hughston Sports Medicine Foundation, Inc., Columbus, Georgia).

The articular cartilage is continuous with the synovium, or synovial membrane. This synovium is a vascular mesenchymal tissue that lines the joint space and produces the joint fluid that serves to lubricate, nourish, and remove cellular debris within the joint capsule.

Trauma to a large synovial joint affects primarily the ligamentous, capsular, and cartilaginous structures, but these in turn can affect the osseous structures because of the action and interaction of all anatomic and biomechanical parts. Trauma to the synovial membrane and cartilaginous surfaces is a contributory factor to the later onset of degenerative arthritis. Miltner et al. (9) pointed out that this synovial membrane becomes congested with small hemorrhages, resulting in the formation of pannus at the osteocartilaginous junction. This causes fibrillar degeneration of the surface layers of cartilage on the side of injury and cell damage and Assuring of the intermediate layer of cells on the opposite side. This latter change is the primary culprit in the onset of late traumatic arthritis.

Ligament injuries may be complete or incomplete. Complete ligament injury will result in demonstrable instability that if left untreated may become permanent and cause

Medial Tibia Attachments

Fig. 18. Proximal view of the posterior and medial tibia showing the soft tissue attachment sites.

Tibial collateral ligament

Fig. 18. Proximal view of the posterior and medial tibia showing the soft tissue attachment sites.

irreparable damage to cartilaginous and osseous structures. Repeated microtrauma can lead to the same sequence of hemorrhage, pannus, and fibrillar degeneration.

Postmortem evidence of these injuries and instabilities can be seen in and around the ends of long bones. They are sometimes overlooked or attributed to the general condition of "arthritis." For forensic identification experts, however, it is important to be able to recognize and classify evidence of knee injuries and specific stress that may offer clues leading to identification of the victim.

As a consequence of diagnostic coding protocols that have been established by the health insurance industry, the recognition and exact classification of an injury is often

Posterior View Nerve Supply The Knee
Fig. 19. Anterior and posterior views of a right patella. The top two views show the bony topography of the patella. The bottom two views indicate the attachment sites of soft tissues.

necessary to trace an individual's medical history. The ability to provide autopsy documentation that an individual at one time likely sustained an "acute avulsion of the anterior cruciate ligament" or a "lateral tibial plateau fracture" will prove to be an advantage when attempting to match damaged, decomposed, or skeletal remains with the medical records of missing persons.

This section will illustrate the typical appearance of bones that have incurred repeated mechanical stress and some of the most common knee injuries.

Femur: STRESS RELATED:

Age-related gonarthrosis (Fig. 21) Injury-related gonarthrosis (Fig. 22) Suprapatellar plica anatomy (Fig. 8) Suprapatellar plica defect on bone (Fig. 23)

Fabella Radiology

Fig. 20. Articular surfaces of a fabella and a toe sesamoid. The articular surface of the fabella is gently concave in superior-inferior and medial-lateral directions. There is a central convex curve in a toe sesamoid (7).

Fig. 20. Articular surfaces of a fabella and a toe sesamoid. The articular surface of the fabella is gently concave in superior-inferior and medial-lateral directions. There is a central convex curve in a toe sesamoid (7).

Fabella articulation (Fig. 24) Subluxing patella (Fig. 25) Osteochondritis dissecans (Fig. 26) Pellegrini-Steida disease (Fig. 27)

INJURY RELATED:

Supracondylar and condylar fractures (Fig. 28) Ligament avulsions (Fig. 29)

Tibia: STRESS RELATED:

Meniscal wear (Fig. 30) Age-related gonarthrosis (Fig. 31)

INJURY RELATED: Condylar fractures (Fig. 32) Tibial plateau fractures (Fig. 33) Avulsion fractures (Fig. 34) Osgood-Schlatter disease (Fig. 35)

Patella: Patellar injuries (Fig. 36)

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